Where does Daphnia live? Description and the whole truth about water flea bites Reproduction of daphnia in summer asexual reproduction

Daphnia is a small crustacean that belongs to the Daphniidae family. Because of the peculiar sharp shocks in the water, it received a second name - a water flea. Now used as live food for aquarium fish ok, which is grown even at home.

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Description

Daphnia is a tiny crustacean with miniature sizes (1-6 mm). It lives in all freshwater continental reservoirs with stagnant water or a slow current. In rivers, lakes, ponds, there can be a high population of daphnia. These are planktonic crustaceans that spend most of their time in the water. There are a number of species that live in temporary water bodies. Some species can live in arid regions - these are halophiles, preferring salty, brackish continental waters. These include the following species: daphnia atkinsoni, daphnia magna, mediterranean, and others.

Daphnia spend most of their lives in the water column, moving in sharp leaps, and waving their antennae, which are covered with special bristles. Many species of daphnia are able to crawl along the bottom or walls of containers under the stimulus of the flow of water, which creates pectoral legs. During this process, the antennas remain stationary. IN summer time Daphnia lives in lakes, rivers and ponds with flowering water, where the level of accumulation of cyanobacteria is high. These crustaceans are very prolific and multiply rapidly.

breeding process

The ability of self-reproduction without the need for heterosexual reproduction, when the offspring entirely inherits the parent's genotype, is parthenogenesis. Daphnia can reproduce at a high rate shortly after hatching from the eggs. IN natural conditions, V recent months spring, summer and autumn, regardless of temperature, nutrition, these crustaceans reproduce by parthenogenesis, and give birth to about 10 larvae. During these seasons, only females live in reservoirs.

Embryos can be seen through the mother's body without the use of a microscope. Females of the next generation will be able to prepare for parthenogenesis on the 4th day of life, and give birth to nauplii every three days. Behind life cycle females can reproduce 25 generations of crustaceans, in general, she will give birth to about 100 fry. If there is not enough food, eggs can develop in males, at which time the females produce eggs that need to be fertilized. It will develop into tiny embryos that will hibernate and become covered in a saddle-shaped shell called the ephippium.

With such a metamorphosis, Daphnia is able to survive harsh conditions. environment, even dried up reservoirs or its glaciation. The females that will appear to form the ephippium are easily distinguished - they have a dark spot on the body in the back of the body. Partogenetic broods do not have it. With the resumption of favorable environmental conditions, a generation will appear from the eggs, which will give birth exclusively to females, and all born males will die until adverse conditions resume.

How to catch daphnia?

Daphnia are caught with a net. You should choose a special net, with a handle 3 meters long, 30 cm in diameter, and a cloth cone 60 cm long, rounded at the end. The net ring can be made of durable material - stainless wire 4-5 mm. If made from a thin material, then it will bend strongly, and can tear, catching on the bottom snags. As a fabric for a net, synthetic ones are suitable - nylon, nylon. They do not rot after contact with water. The mesh size of the cell should depend on the number of crustaceans caught.

Look at catching daphnia from a pond.

Having prepared a net, you can look for a reservoir. It is desirable that it be clean and that no fish live in it. Daphnia from dirty water bodies can introduce an infection into the aquarium water. Fish food must be caught carefully: take a net, and with slow, careful movements lead it to the places where daphnia accumulate. Check the catch, shake it into a container of infused water, and continue fishing. In a crowded net, the crustaceans will die, so it is better to take out the prey in small portions.

It is possible to catch fish food in shallow puddles, but it is difficult to use a standard net in them. Use a net with a short cone so that it does not cling to the bottom and raise turbidity. To prevent hydra from getting into the catch with daphnia, catch them away from algae and aquatic plants to which hydra can attach. You can not catch food for fish in a reservoir that is located near industrial areas.

Next, the caught fish food must be placed in a container for transportation. It can be a glass jar, a can or a can. Before that, strain the daphnia through a net with small cells to remove garbage, beetles, and insect larvae that have fallen into the catch. The container should have a compressor with aeration so that most of the catch is preserved while it is delivered home.

Next, the crustaceans should be poured into a vessel with a wide bottom. After some time, unwanted organisms will settle on the bottom and walls of the tank. You can find larvae, leeches, insects, which are superfluous here. There you will also see daphnia that did not survive. Water from a container where daphnia already lives cannot be poured into an aquarium. These crustaceans are recommended to feed small aquarium fish - guppies, neons, tetras, mollies.

In the warm season, daphnia can also be dangerous for aquarium owners. In summer and spring, crustaceans feed on the pollen of flowering plant species, which are brought into the reservoir with the help of wind. Crustaceans caught during these seasons while feeding the fish cause painful allergic reactions in humans. It is during the warm seasons that the crustaceans are saturated with pollen, so there is an opinion that aquariums are unhealthy.

See how to grow daphnia at home.

How to breed at home?

You can grow daphnia at home in a 20-liter glass or plastic container. Do not use for growing containers that can release toxic substances. If you use metal containers, then they must be made of stainless steel. Aluminum oxides form a film that can be toxic. Daphnia is demanding on the oxygen content of the water, so the bottom area of ​​the tank should be wide. In the summer, you can place a 50-liter container outside, where the future fish food will grow better.

The optimal diet for daphnia is blue-green algae. Also, crustaceans can be given yeast in a pea-sized portion, diluted in water. At home, fish food is recommended to be grown at a temperature of 20-22 degrees Celsius. All types of daphnia adapt to wide temperature ranges. Maximum range: 10-30 degrees.

Daphnia is susceptible to cloudy and dirty water, but there should be enough oxygen in the water, install a compressor in the tanks for keeping and diluting. These crustaceans form hemoglobin, so even in the absence of oxygenated water, they can survive, but not for long. But they do not tolerate aeration with small air bubbles, as they can destroy them. Home grown fish food is safe and healthy for your fish.

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Daphnia are predominantly small crustaceans belonging to the Daphniidae family. This family, in turn, is included in Cladocera, which also includes gammaruses, brine shrimp, and others. For peculiar sharp movements, it is often called the "water flea". Not to mention the features of movement, daphnia appearance also looks like a flea. However, the latter belongs to insects and has a very distant common ancestor with crustaceans, since both classes are included in the phylum Arthropoda. All types of daphnia have different variations, and sometimes representatives of the same species are very different from each other. Features of the phenotype, size and shape of the body depend on the area of ​​​​origin and specific environmental conditions. Representatives of the genus Moina have a significant similarity with Daphnia.

It is important to distinguish daphnia from other "water fleas" such as copepods, cyclops species, and barnacles, which often inhabit the same areas. Sharp movements, body shape and, to a lesser extent, coloration, are the best criteria for distinguishing without the need for examination under a microscope.

The genus Daphnia has a very wide distribution, including Antarctica, where Daphnia studeri, previously attributed to the genus Daphniopsis, was found in the relict salt lakes of the Vestfold oasis. At the beginning of the 20th century, the opinion about the cosmopolitan distribution of most species prevailed, but later it turned out that the faunas of different continents differ greatly. Some species, however, have very wide ranges and are distributed on several continents. The smallest number of species is characteristic of the equatorial regions, where daphnia are rare. The fauna of subtropics and temperate latitudes is the most diverse. In recent decades, the ranges of many species have changed due to their dispersal by humans. Thus, a species from the New World, D. ambigua, was introduced into Europe. In many reservoirs in the southern United States, D. lumholtzi has become common, which until then was found only in the Old World.

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In ponds and puddles of central Russia, they are often found, and therefore the most popular among, are the following crustaceans of the genus Daphnia. Daphnia magna (D. magna), female - up to 6 mm, male - up to 2 mm, newborns - 0.7 mm. Ripen within 10-14 days. Litters in 12-14 days. In laying up to 80 eggs, but usually 20-30. The life expectancy of this crustacean is up to 3 months. Daphnia puleks (D. pulex), female - up to 3-4 mm, male - 1-2 mm. Litters in 3-5 days. In laying up to 25 eggs, but usually 10-12. Pulex live 26-47 days. In the lakes of the temperate zone of Eurasia, D. cucullata, D. galeata, D. cristata and several other species are often found.

Daphnia are small crustaceans, the body size of adults is from 0.6 to 6 mm. They inhabit all types of stagnant continental water bodies, and are also found in many slow-flowing rivers. In puddles, ponds and lakes, they often have a high abundance and biomass. Daphnia are typical planktonic crustaceans, spending most of their time in the water column. Various species inhabit shallow temporary water bodies, littoral and pelagial lakes. Quite a few species, especially those inhabiting arid regions, are halophiles living in brackish, saline and hypersaline continental water bodies. Such species include, for example, D. magna, D. atkinsoni, D. mediterranea, as well as most of the species previously assigned to the genus Daphniopsis.

Most of the time they spend in the water column, moving in sharp leaps due to the flapping of the second antennae, which are covered with special feathered bristles. Many daphnia are also able to slowly crawl along the bottom or walls of blood vessels due to water currents created by the pectoral legs; the antennae are motionless during this method of movement.

Perhaps the elusiveness of rapidly jumping crustaceans reminded scientists of the legend of the nymph Daphne, almost overtaken by Apollo, but never caught by him? Or maybe the mustache of the crustaceans seemed to someone like the branches of an evergreen laurel, into which a beautiful nymph has turned.

Ovid in the poem "Metamorphoses" told how one day the golden-haired god of light Apollo inadvertently laughed at the son of Aphrodite Eros (or, as the Greeks also called him, Eros). The offended god of love from a golden bow struck the silver-faced patron of the muses in the very heart. Having once met the beautiful Daphne, daughter of the river god Peneus, Apollo fell in love with her at first sight, but the beautiful nymph, whom Eros struck with an arrow that kills love, started to run away from him with the speed of the wind. Then Apollo chased after her, but the nymph only ran faster and faster from the beautiful god. When her strength began to dry up, Daphne began to beg her father to deprive her of her appearance, which brought her only grief. Old Peney took pity on his daughter. And at that moment, when it seemed that Apollo had already caught up with the beauty, she turned into a laurel tree.

The saddened Apollo did not want to part with his beloved. He decorated his quiver and cithara with laurel leaves, and placed a wreath of laurel branches on his head, the aroma of which always reminded him of the elusive Daphne.

Reproduction in nature

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IN summer months daphnia are often found in flowering ponds and lakes that have a high concentration of algae. The fertility of Daphnia is simply amazing, which is associated with the implementation of parthenogenesis.

Parthenogenesis is the ability of self-reproduction without the need for fertilization, when the offspring completely repeats the parent's genotype, and any differences in the physiological state are determined by environmental conditions. Parthenogenesis allows daphnia to reproduce rapidly in favorable conditions, shortly after hatching from eggs. In nature, in late spring, summer and early autumn, depending on temperature, food availability and the presence of their metabolic products, daphnia reproduces parthenogenetically, giving rise to an average of 10 nauplii per adult. During this period, only females are present in the reservoir. The developing embryo is often visible inside the mother's body without a microscope. Females of the next generation are capable of parthenogenesis after 4 days of development, while childbirth occurs every three days. During her life cycle, a female may give birth 25 times, but in practice this number is slightly less and the female tends to produce no more than 100 offspring.

With a lack of food, some eggs develop into males, and females begin to produce eggs that must be fertilized. The latter develop into small embryos which then hibernate, covered with a dark brown/black saddle shell known as the ephippium. In this form, daphnia can tolerate harsh environmental conditions, short-term drying of the reservoir and even its freezing. Females born to form ephippium are easily distinguished from parthenogenetic individuals because the developing ephippium is present as a black spot at the posterior end of the body. When environmental conditions become favorable again, a generation appears from the eggs, which, in turn, gives birth only to females, while all males die before the onset of unfavorable conditions.

Fishing in natural waters

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They catch daphnia with a net. A net for this needs a special one - with a long handle up to 2-3 meters, usually made up of several screwed segments, about 25-30 cm in diameter and a fabric cone about 50-60 cm long with a rounded end. The net ring is made of durable material, such as stainless steel wire with a diameter of 3-5mm. If you make it thinner, it will easily bend, and taking into account possible snags at the bottom ... But the most difficult thing is to choose a fabric for the net. Here, synthetic materials are preferable, such as nylon, which do not rot from prolonged contact with water. The size of the net mesh depends on what you are going to catch, a very small fabric greatly slows down the net in the water, so it is better to have several interchangeable rings with different fabrics for catching food of different sizes.

The net works calmly, smoothly, without much effort leading it with the “eight” in places where daphnia accumulate. We spent a couple of times, took it out, shook out the catch, and began to fish further. If you push a full net, then many daphnia crumple and die, so it is better to take it out more often with small portions of prey. And then greed, you know, does not lead to good. For fishing, it is better to prefer smaller reservoirs, for example, the same puddles - there daphnia are more accustomed to oxygen starvation and will more easily endure further transportation. True, it is difficult to catch with a typical net in small puddles, there you have to use a net with a shorter cone - otherwise it starts to cling to the bottom and understand the turbidity. In order not to catch hydra with daphnia, one should try to catch prey away from thickets of aquatic plants or objects in the water to which it can be attached. And in no case is it recommended to catch food in reservoirs where fish live - with such food it is easy to introduce pathogens of various diseases.

Captured daphnia are placed in a container - a can or a special cann for transportation. It is advisable to strain the catch through a sparse mesh before pouring to remove any debris and any large unwanted guests - swimming beetles or large dragonfly larvae. It is highly desirable to have a battery-powered compressor in the transport tank - it will allow you to keep most of the catch alive during the journey home.

Houses of captured daphnia are poured into a wide flat vessel, such as a white enameled basin. There, for some time, all unwanted organisms settle on the bottom and walls, on a white background it is easy to detect dragonfly and leech larvae, and everything else that has nothing to do with daphnia. In the same place, dead crustaceans accumulate at the bottom. When feeding, daphnia are caught with a net, the water in which they are located cannot be poured into the aquarium! These crustaceans are best suited for feeding small aquarium fish, such as or. For larger fish it is more convenient to use live or frozen.

In nature, daphnia live in ponds and large puddles, where they feed on various bacteria and phytoplankton. However, these reservoirs are often polluted. industrial waste Or they have fish in them. Both can lead to diseases in aquarium inhabitants.

Daphnia can also be dangerous for the aquarists themselves. In spring and early summer, the diet of crustaceans often includes pollen from flowering plants, carried by the wind into water bodies. Daphnia caught at this time and dried for future use when feeding fish can cause a painful reaction in people suffering from pollen allergies. This fact, in particular, can explain the often encountered opinion that the aquarium is harmful to health. In fact, the reason is pollen, which during the period of mass flowering of grasses is literally “stuffed” with crustaceans.

Breeding at home

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For growing daphnia, a 15 liter plastic container, or any other, is perfect. In this case, several recommendations can be noted. Avoid container material that is water soluble or releases harmful chemicals. If a metal container is used, it must be made of stainless steel. Aluminum oxides form a film, but some aluminum is still released. As in the case of a conventional aquarium, a large area of ​​​​contact with air is necessary for gas exchange, because daphnia are very demanding on the oxygen content. If the container is located outdoors, in strong sunlight or other lighting, it is recommended to use more than 40 liter volumes in order to water environment was stable. In addition, when black pond material is used, it heats up more than transparent or yellow, which should also be taken into account.

For those who wish to have a small number of daphnia per week, the culture can be maintained in a two liter bottle. For growing in an aquarium, it is a good idea to connect the lighting through a timer, which can be purchased at an electrical appliance store. Daphnia magna has been found to prefer low aeration. In theory, aeration not only supports gas exchange, but also stabilizes water conditions and prevents crop inhibition. Daphnia pulex also likes low aeration. It is necessary to avoid small air bubbles that can get under the daphnia carapace, raise them to the surface, interfere with feeding and eventually lead to death.

The best nutrient medium for the culture are blue-green algae. They are usually free-floating green algae that tend to turn water into "pea soup", yeast (Sacromyces spp and similar fungi) and bacteria. The combination of the above objects makes the culture maintenance process successful, yeast and algae complement each other.

frozen daphnia
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Microalgae are consumed by daphnia in huge quantities, and an abundance of crustaceans is observed in places where water bodies bloom. There are a number of ways to ensure the development of algae that require minimal effort.

Placing the culture container in direct sunlight guarantees algae development within two weeks, usually earlier. Their spores are airborne and colonize water bodies, but, as a rule, some algae is added to the water to speed up flowering. Use of plant fertilizers, such as Miracle grow. Once a week, 1 teaspoon of fertilizer is added to a 4 liter container. The container must be placed in direct sunlight. Aeration and slow movement of water is necessary. A system must be built whereby the first algae tank already has green color, the second will acquire this shade within two days, the third within two more days, etc.. When the first container becomes light green (after 2 weeks), it is poured into the Daphnia culture. The empty container is refilled with the mixture with the addition of a small amount of water from the second container. Thus, every two days the aquarist has 4 liters of blooming water ready to be fed to the daphnia.

The advantages of algae are the ease of preparation and the extremely rapid development of the culture of daphnia that consume them. There are no disadvantages, except for the need to constantly restart the tanks. Daphnia should not be placed in an environment that is too rich in algae, because algae tend to raise the pH up to 9. High alkalinity is associated with an increase in ammonia toxicity, even at low concentrations.

Bakers', brewers', and virtually all other types of yeast are suitable for daphnia cultivation, but it is recommended that no more than 28 g per 20 liters of water be used daily. In the case of using yeast, algae can be added to the water, which will prevent environmental pollution. It is important not to overdo it with the addition of yeast, excess will pollute the environment and destroy the daphnia culture.

dried daphnia
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Some baker's yeast comes mixed with active ingredients such as calcium sulfate, ascorbic acid which stimulate the development of fungi. These components themselves are harmless to the culture, however, ascorbic acid can lower the pH of the medium to 6, which is far from ideal for Daphnia. This usually happens with overfeeding.

The advantage of yeast as a nutrient medium is that it is easy to obtain and requires minimal effort to prepare and maintain the culture. However, they are not as valuable in terms of nutrition for daphnia as algae. Crustaceans need to consume more yeast than algae to obtain the same nutritional value.

Daphnia lives in a wide range of temperatures. The optimum temperature is 18-22 0C. D. pulex thrives at temperatures above 10 0C. Moina withstands even more severe fluctuations, 5-31 0C; the optimum is 24-31 0C. The increased resistance of Moina to temperature indicators makes it a preferred object of cultivation, when for D. magna in natural conditions the optimum is reached only once a year.

Daphnia are tolerant of dirty water, and dissolved oxygen levels can range from near zero to supersaturated. Like brine shrimp, the ability of daphnia to survive in an oxygen-poor environment is due to the ability to form hemoglobin. Hemoglobin production can be accelerated by increasing temperature and population density. As well as in the case of Artemia, Daphnia does not tolerate active aeration with small air bubbles that can kill it.

Daphnia production is a relatively easy process. However, there are measures to increase the productivity of cultivation. Good aeration, good to the extent that the water is oxygenated, but not overly aerated, is a major factor in increasing productivity. Some species prefer no aeration, but Daphnia magna is best bred in its presence. In addition, this allows you to increase the density of the culture, the circulation of water reduces algal plaque on the walls of the vessel, and also transfers food particles to a suspended state, which is typical for the natural diet of daphnia. The only drawback is that small air bubbles fill the carapace of crustaceans, which float up and cannot feed. Air atomizer should be avoided altogether, or it should be very coarse to create large bubbles. Convenient in terms of aeration is the "bio-foam" filter. It is usually used in a fry tank but is ideal for Daphnia. It captures large particles and promotes their decomposition to feed the algae.

Regular selection/collection of culture. This event maintains a constant increase in culture and provides daphnia with the opportunity to accumulate oxygen and food faster. 24-hour daylight hours increase the productivity of daphnia, but this is an optional measure. Also, do not keep Daphnia in the dark for 24 hours, because this stimulates the crustaceans to form ephippia. The mode and degree of water replacement depends on the nutrient medium used, but, in any case, they are necessary for purification from metabolites and toxins.

When it comes to cultivating Daphnia, harvesting it can be a real challenge, but it is an integral part of the whole breeding process. Otherwise, overpopulation becomes a serious problem. Even if you have to shake out the crustaceans in the sink, this must be done, because the culture can become unstable. If the aquarist cultivates daphnia at temperatures below 25 0C, it makes sense to start catching in the middle of the second week. This is because most crops take several days to adapt and start reproducing. When culling / trapping, a net is used that has meshes large enough to pass young crustaceans, but small enough to catch adults. Some aquarists recommend pouring ¼ of the container through the net and then refilling the volume with fresh water and culture medium. No more than ¼ of the population can be caught daily, which also depends on the quality of cultivation. Catching can be done during the day when aeration stops, when all daphnia rise to the upper layer of water.

Caught crustaceans can live for several days in a jig with fresh water. They exhibit normal activity at elevated temperatures. However the nutritional value daphnia is gradually reduced because they are starving and for the best effect it is necessary to provide them with food. For a long time, crustaceans can be stored frozen if they are frozen in water with a low salt content (0.007 ‰, density - 1.0046). Of course, this will kill the daphnia, by washing out the nutrients, their value will decrease, almost all enzymatic activity will be lost within 10 minutes, and after an hour ½ of the free amino acids and all related ones will be lost. Fish are not so willing to eat frozen crustaceans.

daphnia magna
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Daphnia has long been used as a quality feed for. In Soviet times, aquarists caught these crustaceans in natural reservoirs and used them live, dried or frozen. Dried was used in pure form or mixed with other dry food.

It is difficult to keep a large number of this crustacean alive at home, so freezing them during mass reproduction in nature would be optimal. Frozen food is practically not inferior in nutritional value to live crustaceans. Now frozen daphnia can be bought at pet stores and self-harvesting of this crustacean is a thing of the past.

Structure

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A little more about the structure of daphnia. This name is used by aquarists for various cladocerans. You can get an idea of ​​their appearance in the photo. In all representatives of daphnia, the body is strongly compressed from the sides and covered with a chitinous bivalve shell fastened on the back. There are two eyes on the head, which in mature individuals can merge into one compound eye, and in some species there may be another additional eye next to it.

Also on the head are two pairs of so-called antennae, the rear of which are large and additionally equipped with bristles that increase their area. It is due to the swing of these antennae that daphnia move in the water. When rowing with antennas, the body of the crustacean receives an abrupt forward movement, for which Daphnia received the second, popular, name "water flea".

Daphnia reproduce quite unusually from a human point of view. Females have a cavity called a "brood chamber" located on their back and protected by the upper edge of the shell. In the summer, if the conditions are favorable, unfertilized eggs are laid in this cavity, in the amount of 50-100 pieces. That is where they develop. Only females are hatched from them, which leave the chamber, and the adult female then molts.

A few days later, the process is repeated. Young females during this time also grow up and are connected to the breeding process. With a successful combination of circumstances, reproduction proceeds like an avalanche. This is where in the summer in small reservoirs daphnia often just teems, and the water seems to be colored reddish.

With a decrease in air temperature, at the end of summer and at the beginning of autumn, males begin to appear from some of the eggs, they fertilize the females and they have eggs enclosed in a dense shell. They are called ephippies. They are able to withstand drying and winter frosts, and can be carried with dust. Next spring, warmth and moisture will awaken them to life. The females will hatch and the cycle will repeat.

Kinds

Pulex
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Most often, daphnia are found in stagnant water bodies - puddles, ponds, lakes, ditches, pits with water. Their mass quantity, suitable for self-harvesting, can be detected by coloring the water in red or gray-green. They feed on bacteria, ciliates and plant plankton, creating a stream of water with the help of the movement of antennas.

When catching daphnia on your own, you need to take into account that they react strongly to lighting. With a strong one, they will tend to go deep into the water, and with a weak one, up or towards the light source.

In the middle lane, the following types of crustaceans are most common:
the largest - the size of the female is up to 6 mm, the male is up to 2 mm, the larva is 0.7 mm, grows within 4-14 days, the breeding interval is 12-14 days, in one clutch up to 80 eggs, lives 110-150 days;
crustaceans of medium size, daphnia pulex, female up to 3-4 mm, breeding period 3-5 days, clutch up to 25 eggs, lives 26-47 days.
small crustaceans, up to 1.5 mm: types of genera, female up to 1.5 mm, male up to 1.1 mm, larva 0.5 mm, matures during the day, litters every 1-2 days, up to 7 litters, up to 53 eggs, lives 22 days.

The stomach of freshly caught or freshly frozen crustaceans is usually full of plant foods, so they are useful for feeding aquarium fish deprived of their natural diet. The shell of daphnia, which consists mainly of chitin, is not digested, but nevertheless serves as a valuable ballast substance that activates the work of the intestines of fish that are deprived of the opportunity to actively move in the aquarium. The smallest daphnia moina, having vernacular name“live-bearer”, well suited for feeding grown-up juveniles of aquarium fish.

Catching daphnia

Moina
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When catching crustaceans on your own, it should be taken into account that in the reservoirs where moins, puleks and magna live, there is a consistent change in the number of their populations. After the death of spring phytoplankton, a large number of moins appear, which are replaced by daphnia pulex, followed by magna.

They catch daphnia with an ordinary cloth net, choosing the size of the cell, depending on the desired size of fish food. You can do it differently, catch with a net made of very fine fabric, and then pass it through sieves with different cells, sorting the food by size. You can catch daphnia from spring to late autumn, until a crust of ice appears.

You need to choose sections of the coast protected from the wind or get up on the windward side. Usually this is morning or evening in calm weather, in the absence of bright lighting. In such conditions, daphnia rise closer to the surface of the water. Daphnia are transported in cans, which are shaken out of the net when fishing. It should be borne in mind that if the density is too high, the crustaceans may die on the way home. When sorting, washing and feeding, a sharp estimate of the water temperature is not allowed, daphnia can simply die.

Keeping daphnia alive at home is not easy. The fact is that they are demanding on the oxygen content in the water. Therefore, it is necessary to keep crustaceans in large low enameled or plastic vessels with a large surface, in a cool place, not accessible to direct sunlight. To increase the density of planting crustaceans, you have to do aeration, as in an aquarium.

Breeding

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If necessary, a small number of daphnia can be propagated at home. This is rather complicated and is more of an exotic character than actual forage production. When breeding daphnia, baker's yeast is usually used as food. In this case, you can focus on the color of the water in the vessel where the crustaceans are bred. It should be light brownish or greenish.

If the color becomes saturated, then the introduction of yeast should be temporarily (for 1-2 days) stopped until the water clears. You can also use a magnifying glass to inspect the brood chambers in females. If they are empty or there are few eggs, then feeding is not enough and yeast needs to be added. When breeding daphnia, other inhabitants of local reservoirs, including cyclops, should be avoided getting into this vessel.

Finally, a recipe for breeding crustaceans used by aquarists since Soviet times:

A glass or plexiglass vessel is used with a water temperature of 20-24°C, dH 6-18°, pH 7.2-8. Aeration is weak, not raising turbidity from the bottom, the light is not bright, scattered for at least 14-16 hours a day. As feed we use baker's yeast, frozen to brown and diluted in warm water at the rate of 1-3 g per 1 liter of water. It is necessary to give food 2-3 times a week.

The optimal density of crustaceans is 100-150 pieces/l. Every day you need to catch 1/3 of juveniles. Once every 1 - 2 weeks, the vessel must be washed, removing all the dirt, the water should be changed and the culture should be re-bred. It is possible to use several vessels, starting them with a delay of several days, which provides a continuous pipeline of production of daphnia.

There are other feeding options. You can use dried lettuce or nettle leaves. Crushed into powder, they are filtered through cheesecloth and lowered into water. Provide bright light for algae development. When the water turns green, we transfer to a cool shaded place and start the culture of crustaceans. The process also has to be repeated 2-4 times a month. You can also use blood or meat and bone meal at the rate of 0.5 -2.5 cm3 per 10 liters of water.

Cancers are often very small. Such small aquatic animals include daphnia and cyclops. These crustaceans swim in large flocks in the water of ponds and other slow-flowing freshwater bodies overgrown with aquatic plants. Multi-colored dots they flicker in the water. Let's try to catch daphnia with a thick water net and place them in large glass jars or aquariums. From there, they can be easily taken with a pipette and examined under a microscope with low magnification or under a tripod magnifier.

The body of daphnia (up to 5 mm long) is placed in a bivalve chitinous shell. Behind the shell is elongated in the form of a spike. Daphnia's head is not covered by a shell, it has a large black compound eye, and near it a tiny simple eye.

Slightly convex shell valves are transparent. Through them, you can see the contractions of the heart, the movement of blood and the vibrations of the leaf-like legs. In the same way, the entire intestine with food passing through it is clearly visible on live daphnia.

The structure of daphnia is associated with the conditions of its existence. The transparent body makes it hardly noticeable in the water. Unlike crayfish, the light, transparent body of Daphnia is suspended in water. Therefore, her legs are underdeveloped. With them, daphnia mainly renews water near the gill legs located at the base, in addition, by fluctuations, daphnia legs drive small food particles to the mouth.

The main organ of movement of Daphnia is the long branched antennae of the second pair. They support the body of daphnia in the water. Waving its antennae, the animal with sharp movements, as if jumping, moves in the water. Therefore, daphnia is also called a water flea.

The mouth parts of Daphnia are very weak. This is due to its way of feeding: daphnia feeds on small, microscopic sizes, organisms and the smallest organic particles.

Daphnia and related microscopic and semi-microscopic crustaceans are the main food of most fish. Therefore, they are of great practical importance for fisheries. Daphnia is also known to lovers of indoor aquariums. Aquarium fish are mostly fed daphnia.

Scientists have developed methods for the rapid reproduction of daphnia to feed fish bred in the pond farms of our collective farms and state farms. To do this, on the sunny shore of the pond, in which carp fry are grown, a square hole is dug at a distance of 0.5 m from the shore. A mixture of crushed hay and horse or cow manure is placed in this pit. The pit is filled with water from a pond with some daphnia. At a temperature of +18 to +20 ° in the pit, a large number of flagella, infusoria of shoes, ordinary amoebas, green euglena and other microorganisms develop. Eating them, daphnia grow and multiply rapidly. When there are many daphnia and other crustaceans, a groove is made from the pit to the pond and the entire mass of crustaceans is lowered into it. The groove can then be closed and the hole refilled with water. During the summer, you can bring out live food for fish in it several times.

Daphnia are river crustaceans that are widely used in the aquarium hobby, since they are the universal food for many aquarium inhabitants. These crustaceans naturally live in ponds, but breeding daphnia at home is also possible. Most often, at home, such a type of crayfish as a species of Daphnia moina is bred, and it is about how to breed it at home that will be discussed further.

Speaking about how to breed daphnia at home, it is worth preparing not only the container in advance, but also knowing how to feed these microscopic crustaceans and how to create the necessary conditions.

Tara

For growing at home, containers with a volume of 15-20 liters are perfect. In the process of choosing a container, the following recommendations should be taken into account:

Physical conditions for keeping daphnia

1. Salinity. Since these are freshwater crustaceans, then, accordingly, the water in an artificial reservoir should be fresh for them.
2. Oxygen. Daphnia crustaceans are tolerant of oxygen levels in the water, which can vary from zero to saturated. In this case, it is worth saying that daphnia does not tolerate too active aeration of water in an artificial reservoir, with the release of small bubbles, as well as slow aeration with the release of large bubbles that will form foam on the surface of the water.
3. In matters of the level of ammonia in water and the pH level of water - the optimal indicators are the acidity of water in the range of 6.5-9.5 and the optimum indicators 7.2 - 8.5
4. Speaking about the optimal temperature regime, daphnia, photos of which can be found above or in specialized literature, can live in water with a wide temperature range. The optimum temperature for breeding is in the range of 18-22 degrees.

What to feed

If you breed daphnia at home, beginners naturally have a question - how to feed these crustaceans. Daphnia moina in natural conditions feeds on bacteria and yeast, as well as microplanton.

Bacteria can be obtained both from banana peels, food waste, and ordinary excrement, which are pre-soaked in water and infused for several days. As a rule, the water begins to become cloudy, which indicates the reproduction and growth of bacteria - the maximum effect will be achieved in 6-7 days.

Such turbid feed water is added to a container of 450 ml per 20 liters, every 5-6 days.

Yeast is another nutritious food. In this case, the simplest dry baker's yeast or wet ones sold in packs will do. They are brought in at the rate of 28 grams per 20 liters of water - this is the daily norm for daphnia, while adding microscopic algae, which will prevent water pollution and serve as an additional nutrient component for small crustaceans.

The advantage of yeast as a nutritional component is that it is easy to use, purchase, but it is less valuable than algae. Microscopic algae need to be supplied to daphnia in large quantities - you yourself could see that in algal blooms in lakes and ponds, daphnia predominate in large numbers.

The advantage of using algae in nutrition is their ease of use - it is optimal to choose algae of the Scendesmus family, as well as chlorella, which develop in large quantities in a newly equipped, populated aquarium. It is enough to scoop up water from such an aquarium, put it under the sun's rays in a warm place - the algae will actively develop, serving as food for daphnia in the future.

In water containing daphnia, you can add beet juice or cabbage, carrots - 1 tsp. per 5 liters of volume - this will not only diversify the diet of crustaceans, but also serve as a source of vitamins for them. The addition of liquid manure in small doses also gives an excellent effect, but experienced aquarists do not recommend adding milk or hay infusion - they stop the growth and reproduction of daphnia.

Aeration

Speaking about how to breed daphnia, novice aquarists may ask - is aeration necessary when growing and cultivating river crustaceans? Experienced experts say that it is desirable, especially when growing daphnia moina. It enriches the water with oxygen, promotes the development of phytoplankton and prevents the formation of a film on the surface of the water. The main thing is that aeration should be of medium intensity, since a strong air flow will disturb them, and a stream with small bubbles will accumulate under the crustacean shell and raise them to the surface.

How to increase productivity in the process of development?

This process is simple and even a beginner, puzzled by the question of how to breed crustaceans, will cope with it. In this case, take into account a number of specific recommendations:

1. Good aeration, with a uniform air flow and no too small or large bubbles. This is the first condition for increasing productivity in the process of reproduction of river crustaceans. In this regard, experienced aquarists recommend using an airlift filter in containers with daphnia, which is used in cages with fry.
2. Maintaining a clean habitat and regularly changing the composition of the water - if the volume of the aquarium in which the crayfish are kept is large, it is recommended to replace ¾ of the water composition.
3. Regular collection of culture - this will help maintain the constant reproduction and growth of Daphnia at the proper level.
4. A 24-hour daylight day can also increase growth and active reproduction at times. Of course, this is not a prerequisite, but at times increases the growth and reproduction of this river, microscopic crustacean. At the same time, the minimum duration of daylight hours for them should be at least 18 hours.


5. The mode and percentage of water replacement in containers containing daphnia - in this aspect, it is worth considering what feeds are used, how much artificial reservoir and the number of daphnia in it. But in any case, it is necessary to purify water from metabolic products of microorganisms and toxins.

As you can see, breeding daphnia, which serves not only as a nutritious and versatile food for your own fry and fish, but also a great idea for a home business, is quite simple at home.

aquariumax.ru

Systematics[edit | edit code]

One of the largest (more than 50 valid species in the world fauna) and complex taxonomy of Cladocera genera. Type view - D. longispina O.F. Mueller, 1785. The most characteristic distinguishing feature of the genus is antennae I of females fused with the head. In addition, the rostrum is usually well developed in females, and the ventral margin of the valves is convex. In both sexes, the valves, as a rule, bear spines and form an unpaired outgrowth - a tail needle. In most species (except for some Australian species, often assigned to the genus Daphniopsis) Ephippium has two eggs. All setae of antennae II ordinary, with long setulae.

Most taxonomists recognize the division of this genus into two subgenera - Daphnia (Daphnia) O.F. Mueller, 1785 and Daphnia (Ctenodaphnia) Dybowski et Grochjwski, 1895. In subgenus Daphnia (Daphnia) notch of head shield absent, egg chambers of ephippium usually almost perpendicular to dorsal margin of valves. The representatives of the subgenus Daphnia (Ctenodaphnia) notch of head shield present, egg chambers of ephippium usually nearly parallel to dorsal margin of valves. All species previously assigned to the genus Daphniopsis, are part of the subgenus Daphnia (Ctenodaphnia), and many of them have primitive (lack of notch in the head shield) or evasive (one egg in the ephippium) characters.

Daphnia species[edit | edit code]

• Daphnia ambigua Scourfield, 1947
• Daphnia atkinsoni Baird, 1859
• Daphnia arcuata Forbes, 1893
• Daphnia australis(Sergeev and Williams, 1985)
• Daphnia barbata Weltner, 1898
• Daphnia bolivari Richard, 1888
• Daphnia brooksi Dodson, 1985
• Daphnia carinata King, 1852
• Daphnia carvicervix Ekman, 1901
• Daphnia catawba Cocker, 1926


• Daphnia cheraphila Hebert and Finston, 1996
• Daphnia chevreuxi Richard, 1896
• Daphnia cristata G. O. Sars, 1862 – crested daphnia
• Daphnia cucullata G. O. Sars, 1862)
• Daphnia curvirostris Eylmann, 1887
• Daphnia dadayana Daday, 1902
  sensu Paggi, 1999
• Daphnia dubia Herrick, 1883
• Daphnia dolichocephala G.O. Sars, 1895
• Daphnia ephemeralis(Schwartz et Hebert, 1985)
• Daphnia exilis Herrick, 1895
• Daphnia galeata G. O. Sars, 1864
• Daphnia gessneri Herbst, 1968
• Daphnia hispanica Glagolev et Alonso, 1990
• Daphnia hyalina Leydig, 1860
• Daphnia jollyi Petkovski, 1973
• Daphnia lacustris G.O. Sars, 1862
• Daphnia laevis Birge, 1879
• Daphnia latispina Korinek and Hebert, 1996
• Daphnia longiremis G. O. Sars, 1862
• Daphnia longispina O. F. Mueller, 1785)
• Daphnia lumholtzi G. O. Sars, 1885
• Daphnia magna Straus, 1820
• Daphnia magniceps Herrick, 1884
• Daphnia mediterranea Alonso, 1985
• Daphnia menucoensis Paggi, 1996
• Daphnia middendorffiana Fischer, 1851
• Daphnia minnehaha Herrick, 1884
• Daphnia nivalis Hebert, 1977
• Daphnia occidentalis Benzie 1986


• Daphnia obtusa Kurz, 1875
• Daphnia oregonensis Korinek and Hebert, 1996
• Daphnia pamirensis Rylov, 1928
• Daphnia parvula Fordyce, 1901
• Daphnia peruviana Harding, 1955
• Daphnia pileata Hebert and Finston, 1996
• Daphnia prolata Hebert and Finston, 1996
• Daphnia psittacea Baird, 1850
• Daphnia pulex Leydig, 1860)
• Daphnia pulicaria Forbes, 1893
• Daphnia pusilla(Serventy, 1929)
• Daphnia retrocurva Forbes, 1882
• Daphnia quadrangula(Sergeev, 1990)
• Daphnia queenslandensis(Sergeev, 1990)
• Daphnia rosea G. O. Sars, 1862
• Daphnia salina Hebert and Finston, 1993
• Daphnia schoedleri G. O. Sars, 1862
• Daphnia similis Claus, 1876
• Daphnia similoides Hudec, 1991
• Daphnia sinevi Kotov, Ishida and Taylor, 2006
• Daphnia stuederi(Ruhe, 1914)
• Daphnia tanakai Ishida, Kotov and Taylor, 2006
• Daphnia tenebrosa G. O. Sars, 1898
• Daphnia tibetana(G.O. Sars, 1903)
• Daphnia thomsoni G.O. Sars, 1894
• Daphnia thorata Forbes, 1893
• Daphnia triquetra G.O. Sars, 1903
• Daphnia truncata Hebert et Wilson, 2000
• Daphnia turbinata G. O. Sars, 1903
• Daphnia umbra
• Daphnia villosa Korinek and Hebert, 1996
• Daphnia wardi Hebert et Wilson, 2000

External structure[edit | edit code]

Unless otherwise noted, this section describes the structure of females. The covers consist of a head shield and a bivalve carapace. Usually they have a well-marked pattern of rhombuses and polygons - reticulation. Each such cell of the integument is formed by one cell of the hypodermis. There are spines on the edge of the valves, and a tail needle covered with spines at the posterior end. Many species have rows of feathered setae on the inner margin of the valves in its middle part; males of all species have the same setae and additional setae on the anterior-lower corner of the valves.

On the head, most species have a beak-shaped outgrowth - the rostrum. Under it are the first antennae (antennules) - short outgrowths bearing 9 olfactory setae - aesthetasci (aesthetics) at the end, and one additional seta on the lateral surface. In males, the first antennae are larger, mobile; in addition to aesthetasci, they carry a large bristle (“flagellum”) at the distal end.

On the lateral surface of the head there are protrusions of the cuticle - fornixes. Their shape, as well as the shape of the posterior edge of the head shield, is an important diagnostic feature of subgenera and groups of species. Under the fornixes, the second antennae (antennae) are attached to the head with a complex "joint". They consist of a base and two branches - an internal three-segmented and an external four-segmented. At the ends of the segments of the branches there are two-segmented swimming bristles covered with flattened hairs, forming "oars" when swimming. There are five of them on a three-segmented branch (four only in D. cristata), on a four-segmented one - four. There are several small sensitive bristles on the base.

A large upper lip extends from the back of the head. Inside it are several giant polyploid cells that secrete a secret that glues food into a food bolus.

On the border between the head shield and the carapace, mandibles are located under the valves. They have a complex shape, are asymmetrical and have highly chitinous chewing surfaces covered with ridges and outgrowths. In the process of feeding, the mandibles transport food to the mouth opening.

Under the carapace are small first maxillae (maxillae), bearing four setae. Maxillae II are reduced in Daphnia. There are five pairs of biramous thoracic legs of complex structure. The legs of the first and partly of the second pair differ in structure in males and females. On the first pair of legs of males there are hook-shaped outgrowths that allow them to cling to females during mating. The third and fourth pairs carry fans of filtering bristles. Each leg has a respiratory appendage - the epipodite.

Behind thoracic region a reduced abdominal is located, the presence of which is “marked” by dorsal abdominal outgrowths that close the exit from the brood chamber. There are usually four of them, they are well developed in mature females and reduced in males of most species.

The posterior part of the body is a large mobile post-abdomen homologous to the telson of other crustaceans. On its dorsal side are two rows of teeth, between which is the anus. In males of some species, these teeth are partially or completely reduced. At the end of the postabdomen there are paired claws covered with spines. According to some data, they are homologous to the furca, according to others, they are a pair of large modified setae. There are spines on the outer and inner sides of the claws, usually there are three groups of spines on the outer side, and two on the inner side. The postabdomen serves to clean the filtration apparatus from large foreign particles.

Internal structure[edit | edit code]

The integumentary system of Daphnia is represented by a typical hypodermis. The hypodermis of the carpax consists of large cells forming rhombic-shaped cells.

Central nervous system consists of the supraesophageal ganglion (brain) and the ventral nerve cord with several paired ganglia. The brain is clearly visible in living individuals, which is extremely rare. It consists of a large, bisected optic ganglion and the supraesophageal ganglion proper. From the anterior part of the optic ganglion, the optic nerve departs, connecting the brain with a complex compound eye. The unpaired compound eye in Daphnia is formed from a paired primordium (embryos have two eyes) and contains exactly 22 facets (ommatidia). It is located in a special cavity inside the head, to the walls of which it is suspended with the help of two ligaments (ligaments) and is set in motion by three pairs of oculomotor muscles. In living individuals, an eye tremor is noticeable, larger jumps (saccades) of the eye are observed from time to time. Nerves also depart from the brain to the ocellus (simple eye), the first antennae (at their base there is a sensitive ganglion, the cells of which innervate the olfactory bristles - aesthetes), as well as nerves to the sensitive occipital organ of unknown purpose. A simple eye (ocellus, nauplial eye) adjoins the lower part of the supraoesophageal ganglion. In most species, it contains pigment and is visible as a small black dot. There are 4 groups of sensitive cells around the pigment spot.

Daphnia has a complex system striated muscles that move the second antennae, postabdomen and pectoral limbs, as well as muscles that move the eyes, upper lip, etc. The muscles of the digestive tract are also striated.

The digestive tract begins with a mouth opening, which is covered by a large upper lip. Giant highly polyploid cells located inside the lip secrete a secret that glues food into a food bolus. With the movements of the mandibles, it is transported to the thin esophagus, the dilator muscles of which create peristalsis, ensuring the transport of food through the esophagus. Inside the head, the esophagus passes into the wider midgut, which extends to the middle part of the postabdomen. Inside the head, two curved hepatic outgrowths depart from the midgut. In the posterior part of the postabdomen is a short hindgut.

The heart is located on the dorsal side of the body, in front of the edge of the brood chamber. Blood (hemolymph), the flow of which is clearly visible due to the presence of colorless cells in it - phagocytes, enters the heart through ostia - two slit-like lateral openings. When the heart contracts, the ostia close with valves, and blood is ejected through the anterior opening to the head. There are no blood vessels, the regular direction of blood flow is provided by transparent partitions between different parts of the mixocoel.

Breathing occurs through the integument of the body, primarily the pectoral legs, on which there are respiratory appendages - epipodites. The latter are also involved in osmoregulation. An additional organ of osmoregulation in newborns is the large occipital pore (occipital organ), which disappears after the first postembryonic molt.

The excretory organs are complex-shaped maxillary glands, which are located on the inner surface of the valves in their anterior part.

Paired ovaries (in males - testes) are located on the sides of the intestine. At the posterior end there is a zone of reproduction of oogonia, the rest of the ovary is filled with maturing oocytes. The eggs, as they mature, move to their posterior third, where narrow oviducts are located that open into the brood chamber. In males, the vas deferens open on the postabdomen in its distal part, in many species on special papillae.

Molt[edit | edit code]

When molting, the cervical suture diverges - the line between the head shield and the carapace, and the animal crawls out of the exuvia. Together with the carapace, the covers of the body and limbs are shed. Moulting is periodically repeated throughout the life of the individual. Usually molting occurs in the water column, ephippial females of some species molt, sticking from below to the surface film of water. Several molts occur during embryonic development, in the brood chamber.

Distribution[edit | edit code]

Genus Daphnia has a worldwide distribution (including Antarctica, where in the relict salt lakes of the Vestfold oasis ( Vestfold Hills) was found Daphnia studeri, previously assigned to the genus Daphniopsis). At the beginning of the 20th century, the opinion about the cosmopolitan distribution of most species prevailed, but later it turned out that the faunas of different continents differ greatly. Some species, however, have very wide ranges and are distributed on several continents. The smallest number of species is characteristic of the equatorial regions, where daphnia are rare. The fauna of subtropics and temperate latitudes is the most diverse. In recent decades, the ranges of many species have changed due to their dispersal by humans. Thus, a species from the New World was introduced into Europe (England) D.ambigua. In many reservoirs in the southern United States, it has become common D. lumholtzi, which until then had only been found in the Old World.

In ponds and puddles of central Russia, the following crustaceans of the Daphnia genus are often found (and most popular among aquarists):

daphnia magna (D. magna), female - up to 6 mm, male - up to 2 mm, newborns - 0.7 mm. Ripen within 10-14 days. Litters in 12-14 days. In laying up to 80 eggs (usually 20-30). Life expectancy - up to 3 months.

daphnia pulex (D.pulex), female - up to 3-4 mm, male - 1-2 mm. Litters in 3-5 days. In laying up to 25 eggs (usually 10-12). They live 26-47 days.

In the lakes of the temperate zone of Eurasia are often found D. cucullata, D. galeata, D. cristata and several other types.

Biology[edit | edit code]

Daphnia are small crustaceans (body sizes of adults are from 0.6 to 6 mm). They inhabit all types of stagnant continental water bodies, and are also found in many slow-flowing rivers. In puddles, ponds and lakes, they often have a high abundance and biomass. Daphnia are typical planktonic crustaceans, spending most of their time in the water column. Various species inhabit small temporary reservoirs. littoral and pelagial lakes. Quite a few species, especially those inhabiting arid regions, are halophiles living in brackish, saline and hypersaline continental water bodies. These types include, for example, D. magna, D. atkinsoni, D.mediterranea, as well as most of the species previously assigned to the genus Daphniopsis.

Locomotion[edit | edit code]

They spend most of their time in the water column, moving in sharp leaps due to the flapping of the second antennae, which are covered with special feathered bristles (hence their common name - “water fleas”, often referred to as all cladocerans). Many daphnia are also able to slowly crawl along the bottom or walls of blood vessels due to water currents created by the pectoral legs (the antennas are motionless during this method of movement).

Nutrition[edit | edit code]

The main food for daphnia are bacteria and unicellular algae. Species that survive the winter in an active state (in deep, non-freezing water bodies) spend it in the bottom layers of water, feeding mainly on detritus. They feed by filtration, creating currents of water with the rhythmic movements of the pectoral legs. Food is filtered out by fans of filtering setae, which are located on the endopodites of the third and fourth pairs of pectoral legs. Large particles stuck in the filtration apparatus (for example, filamentous algae) are removed using the postabdomen and its claws. From the filter fans, food enters the abdominal food groove, is transmitted to the maxillae of the first pair and then to the mandibles, the movements of which transport it to the esophagus. In front, the mouth opening of Daphnia is covered by a large upper lip, inside which are located the salivary glands of giant polyploid cells. Their secret glues food particles into a food bolus.

At an average concentration of feed in water, adult daphnia of various species filter at a rate of 1 to 10 ml/day. Adult daily food intake D. magna can reach 600% of her body weight.

Gas exchange[edit | edit code]

On the thoracic legs are saccular respiratory appendages - gills. Probably, Daphnia get a significant part of their oxygen through the thin integument of the body and limbs, and the respiratory appendages, like the occipital organ of newborns, play an important role in osmoregulation. Some types (for example, D.pulex, D. magna) with a reduced oxygen content in the water, they begin to synthesize hemoglobin, so that their hemolymph and the whole body turn red.

Cyclomorphosis[edit | edit code]

Many species of daphnia (mostly living in lakes) have cyclomorphosis - their different generations, developing in different seasons of the year, differ sharply in body shape. In temperate latitudes, the summer generations of such species have elongated cuticle outgrowths - a tail needle and a helmet of the head shield. In spring and autumn generations, the tail needle is shorter, the helmet may be shorter or absent altogether. It is shown that the growth of outgrowths requires energy costs and leads to a decrease in fertility. Of the factors causing the growth of outgrowths of covers, the influence of increased water turbulence, high temperature, etc. was demonstrated. Later it was shown that the main influence on the growth of cyclomorphic outgrowths is exerted by kairomones, signaling substances secreted by various types of invertebrate and vertebrate predators. Many hypotheses have been put forward about the adaptive role of cyclomorphosis: facilitating soaring in less dense and viscous water, accelerated swimming in a horizontal direction, etc. Most of them are either not proven or refuted. Now, the theory of the role of outgrowths in defense against predators is accepted as the main explanation for cyclomorphosis. Transparent outgrowths increase the actual size of the body and thus protect against small invertebrate predators - more big booty with outgrowths it is more difficult to grab and not release when manipulating - "stuffing into the mouth." Sometimes the tail spine breaks off, which may play the same role as tail autotomy in the lizard. At the same time, transparent outgrowths do not increase the visible size, which is important for protection from large visual predators - fish.

Vertical migrations[edit | edit code]

Like other representatives of zooplankton, daphnia make vertical migrations in many water bodies - both large and deep, and shallow. Almost always, these migrations are diurnal in nature: in the daytime, crustaceans move to deeper bottom layers, and in the dark, they rise to the surface. Among the many theories explaining the causes of migrations, which consume a significant percentage of energy, the most reasonable is now considered the theory that connects migration with the same defense against predators. During daylight hours, larger species, well visible to visual predators, are forced to descend into deep, poorly lit layers of water to protect themselves from being eaten by fish. Migrations in the same species of daphnia can be well expressed in lakes where there are many fish, and absent in lakes where there are no planktivorous fish.

Reproduction and resettlement[edit | edit code]

Most daphnia (as well as other cladocerans) are characterized by cyclic parthenogenesis. Under favorable conditions (for example, in summer in perennial puddles and shallow water bodies), only parthenogenetic females are present in Daphnia populations. From their unfertilized diploid eggs, the next generations of females develop. Since parthenogenesis in daphnia is ameiotic, their reproduction is clonal (populations consist of clones - offspring of individual females). The development of embryos during parthenogenesis proceeds in the brood chamber under the shell and is accompanied by several molts. Then young crustaceans leave the brood chamber (direct development).

In autumn or before the reservoir dries up, males develop from the same unfertilized eggs (as a rule, all individuals of the same litter have the same sex). Thus, sex determination in Daphnia is purely environmental.

The transition to bisexual reproduction in species from large water bodies usually requires the action of two stimuli - a decrease in temperature and a decrease in the length of daylight hours. It is hypothesized that these and other stimuli act through a reduction in the female's food intake. Daphnia males are smaller in size, differ significantly from females in the structure of the first antennae and pectoral legs. They swim faster than females and mate with them by attaching themselves to the posterior edge of the shell. Fertilization in Daphnia is internal.

IN last years it has been shown that the development of males can be induced by the addition of methyl farnezoate, a juvenile hormone of crustaceans, as well as analogs of insect juvenile hormone, the insecticide fenoxycarb, to the medium.

During the period of bisexual reproduction, some females give birth to males, while others at the same time form resting, or ephippial, eggs. They are formed by meiosis and require fertilization for development. After fertilization, they also enter the brood chamber, the integuments of which thicken and form a special chitinous chamber - ephippium (ephippium). Most Daphnia species have two eggs in their ephippium; in some Australian species, often separated into a separate genus Daphniopsis, there is one egg in the ephippium. In species of the subgenus Daphnia the long axes of the eggs are perpendicular to the dorsal margin of the ephippium; in species of the subgenus Ctenodaphnia- parallel to it or inclined at a slight angle. The development of eggs continues until the stage of gastrula, then they fall into anabiosis. During the next molt, the female sheds the ephippium, which in some species usually sinks to the bottom, while in others it floats on the surface of the reservoir. When laying the effipia of the female of some species (for example, D.pulex) often die. Together with ephippiums, daphnia eggs are carried by the wind, spread on the paws of mammals, on the paws and feathers of birds, as well as in their intestines. It has also been shown that floating ephippiums can stick to the body of smooth bugs flying up from the surface of the water and be carried by them, and more often smoothies carry smaller ephippiums. Eggs in a chemically resistant shell inside the ephippia can remain viable after passing through the intestines of birds and fish. They usually also withstand freezing and prolonged drying. It has been shown that resting daphnia eggs can survive and develop for a long time in solutions of poisonous salts (for example, mercuric chloride HgCl 2) at a concentration of poisons thousands of times higher than the MPC; after the rupture of the egg shell, the hatched embryos in such solutions immediately die.

Use in scientific research[edit | edit code]

Daphnia are used as model organisms in many ecological, toxicological and genetic studies.

Deciphering the genome[edit | edit code]

In recent years, a partial decoding of the Daphnia genome has been carried out. Daphnia pulex, in 2011 its draft was completed. The Daphnia genome consists of 200 million nucleotides, but it contains at least 30.9 thousand genes - more than in other multicellular animals studied so far (for example, the human genome contains about 20-25 thousand genes). The Daphnia genome was characterized by a high rate of gene duplications, which led to the creation of numerous gene clusters. More than a third of the gene products found in the Daphnia genome have no known homologues in the proteomes of other organisms. The largest amplified gene families are also characteristic only of this evolutionary line. Many paralog genes are expressed differently depending on environmental conditions; genes unique to daphnia are most sensitive to changes in conditions. It can be assumed that gene duplications increased the ecological plasticity of Daphnia, allowing them to adapt to the conditions of different water bodies and to changing conditions in one water body.

Breeding[edit | edit code]

The cultivation of daphnia as a food object is widespread, both for industrial purposes and by amateur aquarists. Under favorable conditions, daphnia multiply and grow easily and quickly, which makes it possible to obtain 30-50 (in some cases up to 100) grams of crustaceans per day from one cubic meter of culture.

The initial culture can easily be obtained from natural reservoirs. It is advisable to catch crustaceans in small reservoirs, where the population of daphnia can be practically free from the admixture of other animals. In winter, a Daphnia culture can be obtained from ephippial resting eggs collected in advance from the surface of the water or from the upper layer of silt. Collected ephippiums are well preserved in a dry state in a cool room.

Depending on the required number of crustaceans, daphnia can be cultivated both in small vessels and in large pools and ponds. The optimum culture density is 300-1000 g/m³. Periodically, once every few weeks or months, the culture is replanted. The aging of a culture is associated with the accumulation of metabolic and decomposition products in it and with clogging it with other organisms. By changing the water, the life of the culture is extended.

The optimum growing temperature is 15-25°C, the reaction of the medium is neutral (pH 6.8-7.8), the oxygen content is not less than 3-6 mg/l, the oxidizability is 14.8-26.2 mg O 2 /l.

When growing daphnia, both joint and separate cultivation of crustaceans and food for them is used.

When co-cultivated, organic fertilizers are added to the crop, for example, manure applied in an amount of 1.5 kg / m 3. It is possible to grow on mineral fertilizers, the addition of which causes the rapid development of unicellular algae.

The disadvantage of joint cultivation is severe water pollution, rapid aging of the culture and rapid overgrowth of the container with filamentous algae.

Separate cultivation of daphnia and food for them is devoid of these shortcomings, but is technically more difficult and is used mainly in the conditions of mass industrial cultivation of food crustaceans. At the same time, an algal culture is grown separately, which is added 1-2 times a day to a container with daphnia.

In the laboratory and at home, it is convenient to keep a culture of daphnia on yeast, introduced daily a little at a rate of 15-20 g per cubic meter of culture (15-20 mg / l). . Standardized laboratory culture methods for daphnia are described in manuals on toxicology and bioassays.

Other facts[edit | edit code]

Live, dried and frozen daphnia are often used as food for aquarium fish or insects kept in terrariums. In industrial fish farming, the cultivation of daphnia for food is of great importance.

Daphnia is one of the standard objects for testing the toxicity of aqueous solutions of chemical compounds used in the study of aquatic pollution. Daphnia are sensitive even to small concentrations of some salts, for example, the addition of copper salts at a concentration of 0.01 mg / l causes a slowdown in the movements of crustaceans, they either sink to the bottom or freeze at the surface water film.

Literature[edit | edit code]

• Peters P.H., De Bernardi R. Daphnia // Mem. Ist. ital. Idrobiol. - 1987. - V. 45. - 502 p.
• John K. Colbourne, Michael E. Pfrender, Donald Gilbert, W. Kelley Thomas, Abraham Tucker, Todd H. Oakley, Shinichi Tokishita, Andrea Aerts, Georg J. Arnold, Malay Kumar Basu, Darren J. Bauer, Carla E. Cáceres , Liran Carme, Claudio Casola, Jeong-Hyeon Choi, John C. Detter, Qunfeng Dong, Serge Dusheyko, Brian D. Eads, Thomas Fröhlich, Kerry A. Geiler-Samerotte, Daniel Gerlach, Phil Hatcher, Sanjuro Jogdeo, Jeroen Krijgsveld1, Evgenia V. Kriventseva, Dietmar Kültz, Christian Laforsch, Erika Lindquist, Jacqueline Lopez, J. Robert Manak, Jean Muller, Jasmyn Pangilinan, Rupali P. Patwardhan, Samuel Pitluck, Ellen J. Pritham, Andreas Rechtsteiner, Mina Rho, Igor B. Rogozin, Onur Sakarya, Asaf Salamov, Sarah Schaack, Harris Shapiro, Yasuhiro Shiga, Courtney Skalitzky, Zachary Smith, Alexander Souvorov, Way Sung, Zuojian Tang, Dai Tsuchiya, Hank Tu, Harmjan Vos, Mei Wang, Yuri I. Wolf, Hideo Yamagata, Takuji Yamada1, Yuzhen Ye, Joseph R. Shaw, Justen Andrews, Teresa J. Crease, Haixu Tang, Susan M. Lucas, Hugh M. Robertson, Peer Bork, Eugene V. Koonin, Evgeny M. Zdobnov, Igor V. Grigoriev, Michael Lynch, Jeffrey L. Boore. The Ecoresponsive Genome of Daphnia pulex// Science. - 2011. - Vol. 331, No. 6017. - P. 555-561. - DOI:10.1126/science.1197761.
• Ivleva I.V. Biological bases and methods of mass cultivation of fodder invertebrates. - M. : Nauka, 1969. - 171 p.
• Makrushin A. V., Lyanguzova I. V. Invertebrate and plant propagule shell: selective permeability and barrier properties // Journal general biology. - 2006. - T. 67, No. 2. - S. 120-126.
• Shpet G.I. Breeding of daphnia as live food in fish farming // Proceedings of the Ukrainian Institute of Pond. and lake-river. fish household - 1950. - T. 7.
• Guidelines for the determination of the toxicity of waters, bottom sediments, pollutants and drilling fluids by biotesting. - M. : REFIA, NIA-Priroda, 2002.

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Features and habitat of daphnia

Depending on the kind daphnia, their size can vary from 0.2 mm to 6 mm, so study structure of daphnia only possible under a microscope. The body of these crustaceans has an oval shape, it is covered with a special shield of two valves (carapace), which protects the internal organs.

The head is also covered with a chitinous shell and has a beak-like outgrowth (rastrum), under which the anterior antennae are located, which perform an olfactory function.

The size of the rear antennas is much more impressive than the front ones, their main task is the movement of daphnia. Waving both antennas at the same time, daphnia pushes off the water and swims, making sharp jumps. For this feature common daphnia often referred to as the "water flea".

On the head of the crustacean is a compound eye - unpaired organ responsible for vision. The number of facets depends on the species and ranges from 22 to 300. In predatory representatives, the structure of the eye is more complicated and there are more facets. A naupliar ocellus is located just below the faceted ocellus.

Thoracic legs of Daphnia, covered with many bristles, serve as a kind of filter through which the crustacean passes single-celled algae and bacteria suspended in water. The legs make up to 500 strokes per minute.

Daphnia photo, taken at high magnification, make it possible to clearly see and internal structure crustacean. Thanks to the translucent shell, the heart, intestines are clearly visible, and in females, the brood pouch with several embryos.

Daphnia of one kind or another can be found in almost any stagnant body of water - from a small pond to deep lake. Some or other representatives of this genus of crustaceans are found in Eurasia, and South and North America and even in Antarctica.

An important factor in their normal existence is stagnant water, in which there is a minimum number of soil particles. Getting into running water, daphnia filter the soil along with algae and gradually clog their intestines.

Eaten grains of sand accumulate and do not allow the crustacean to move normally, it soon dies. Daphnia is extremely sensitive to environmental pollution, so it is often used to test the quality of water in reservoirs.

The nature and lifestyle of daphnia

Daphnia prefer to spend most of their lives in the water column, where they continuously filter water saturated with single-celled microorganisms. Some species stay near the bottom, feeding on the remains of invertebrates and dead parts of plants. In the same way, daphnia experiences winter cold unless it hibernates.

Nutrition

Blue-green algae, yeast and bacteria are the main food of Daphnia. The highest concentration of unicellular algae is observed in "blooming reservoirs", where, in the absence of a large number of fish, daphnia lives well and reproduces especially intensively.

Reproduction and lifespan

interesting breeding daphnia - class crustaceans are characterized by such a feature as parthenogenesis. This is the ability to reproduce offspring without direct fertilization.

When the living conditions of this genus of crustaceans are sufficiently favorable, Daphnia females reproduce through parthenogenesis, while giving birth only to females.

On average, one individual gives offspring in the amount of 10 nauplii, which in turn become capable of reproduction already on the 4th day after birth. During the period of life, the female daphnia brings offspring up to 25 times.

With the deterioration of environmental conditions, males are also born, and the next generation of crustaceans will reproduce eggs that need to be fertilized. daphnia eggs, formed during such a period, grow into small embryos, they are covered with a special protective shell and go into hibernation.

In this form, Daphnia embryos are able to survive both drought and severe frost. When environmental conditions return to normal, they develop into adults. The next generation will again reproduce only females that will be capable of parthenogenesis.

Another interesting feature of Daphnia is cyclomorphosis. IN different seasons years in the same population individuals are born, different in body shape.

Thus, the summer generations of daphnia have an elongated tail needle and an outgrowth on the helmet. Among the many hypotheses about the appropriateness of such changes, the main one is protection from predators, which are more active in the summer.

The life span of daphnia is short and ranges from 3 weeks to 5 months, depending on the species. Large species such as Daphnia magna outlive their smaller counterparts.

The lifespan of daphnia also depends on the temperature of the water - the higher it is, the faster the metabolic processes proceed, the body develops faster, ages faster and dies.

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Description of the species

Water fleas are very interesting features buildings. Their whole body is dressed in a leathery, two-leaved shell, which ends in two hooks of a specific horn type. One spherical eye is characterized by considerable mobility and consists of a large number of small eyes. On numerous photos taken while observing these living creatures through a microscope, you can consider all the features of such an eye.

The water flea is a typical planktonic crustacean that spends a significant part of its life in the water column. Ponds and puddles located in central Russia are home to the most common species of these crustaceans.

• Daphnia magna. In the photo, a female is clearly distinguishable, with a body length of not more than six millimeters, and a male, having a length of only two millimeters. Individuals in the neonatal period are microscopic in size. The ripening period lasts two weeks. The standard clutch consists of three dozen eggs, which are laid by females every two weeks. Average duration life of individuals does not exceed three months.
• Daphnia pulex. Females of this species have a body with a length of no more than four millimeters. The body of males is two times smaller. This species is incredibly prolific, and clutch occurs every five days and consists of fifteen eggs. The average lifespan can last one and a half months.

In addition, in the photo you can see water fleas of the species cucullata, galeata and cristata, which are frequent guests of temperate Eurasian lakes.

Habitat

The genus of water fleas has a worldwide distribution. Despite the differences in the fauna of all continents, daphnia are found almost everywhere, and a special distribution applies to several continents at once.

Least of all, these crustaceans are found in equatorial regions. The areas most populated by daphnia include the subtropics and temperate latitudes. Currently, there is a significant expansion of the habitat of water fleas, which is due to human activity.

Nutrition Features

Shellfish are very voracious. The main food of Daphnia is represented by bacteria and unicellular algae. For species that survive the winter period in the state of wakefulness, the feeding place is the bottom layers and deep non-freezing reservoirs. Under such conditions, the main food for water fleas is detritus.

Filtration is the way to feed. Equally important is the ability to create water currents through rhythmic movements that are performed by the pectoral legs. To filter food, special fans are used, located on filter-type bristles. Such an organ is located in the areas of endopodites from among the third and fourth pairs of thoracic limbs.

When large particles get stuck in the filtration apparatus, a special organ is triggered, represented by the postabdomen and its claws. Filtering fans serve as a food transfer link to the abdominal food groove, from which it moves to the maxillas and mandibles. The final site for the assimilation of food elements is the esophagus.

Daphnia under the microscope (video)

In the photo you can see a rather large upper lip, which covers the mouth opening of water fleas. Any organs with which bites can be applied are absent in daphnia. The lip is supplied with salivary glands, which include giant polyploid cells. Salivary secretion glues food particles into a single lump. During the day, an adult consumes almost six hundred percent of its own weight.

You may also be interested in the article on moose fleas.

Harm to humans

The lower type of bivalve crustaceans, which include water fleas, do not bite. Any bites that are attributed to daphnia have nothing to do with them. However, Daphnia is really capable of causing some harm to a person, which is associated with a high degree of allergenicity of these crustaceans.

Amateur aquarists quite often use dry food from daphnia, which is a powerful allergen for a quarter of the world's population. Such a high degree of allergy is associated with a dust suspension, which is formed as a result of drying of the crustaceans.

The harm from daphnia is not bites, but an allergy, which is most often manifested by the following symptoms:

• lacrimation;
• conjunctivitis;
• dryness;
• congestion of the sinuses with symptoms of difficulty breathing;
• runny nose;
• involuntary sneezing.

In the next stage, hives and eczema may appear, which are mistaken for bites. In addition, significant skin seals are a bit like flea bites, which are also one of the symptoms of allergies and can provoke severe itching.

Diagnosis of water flea allergy is based on a skin test. Photos of allergic urticaria and eczema are quite reminiscent of flea bites, and a person who is far from medicine should definitely consult with specialists who will clarify the diagnosis and develop an effective treatment regimen.

Despite the fact that water flea bites, as such, are absent, the treatment of allergic manifestations cannot be started. The first manifestations of allergies can be eliminated by using the following drugs:

• antihistamines;
• inhaled type of modern corticosteroids;
• antileukotriene-type drugs.

If the allergy goes into a severe and advanced stage, then the doctor may prescribe bronchodilators, hormonal glucocorticoids, systemic steroid hormones.

How water fleas breed (video)

Daphnia bites are nothing more than a fantasy of most inhabitants. Small crustaceans, of course, can cause some harm, but in most cases it is enough to eliminate the cause of the allergy and remove the primary manifestations of this unpleasant disease in time.

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Fish food

For many decades, pet fish lovers have been using daphnia as food for their aquarium pets. Also in Soviet time these small crustaceans were caught by aquarists in natural reservoirs. It is clear that they had to know exactly where Daphnia lives. Then the caught crustaceans were used not only live, but also frozen and dried. Of course, it is quite difficult to keep a large number of them at home, which is why many people try to freeze daphnia during its mass reproduction in nature. If we talk about the nutritional value of frozen food, then it is practically in no way inferior to live crustaceans. Currently, frozen daphnia can be easily purchased at pet stores, so such an independent preparation is becoming a relic of the past.

The structure of daphnia

I would like to talk a little about how these cladocerans, which we call daphnia, are arranged. Their body is quite strongly compressed from the sides, the latter are covered with a two-fold chitinous shell.

Usually daphnia have two eyes, which are located on the head, but sometimes sexually mature individuals are distinguished by the presence of one compound eye, next to which there may be an additional small eye. On a small head there are also two pairs of antennae. The posterior (second) pair is additionally equipped with bristles and is large. It is thanks to the stroke of these antennae that when Daphnia moves, they make a kind of jump. Therefore, in the people they are also called "water fleas."

Reproduction of crustaceans

If you look at the process of reproduction of these tiny crustaceans from a human point of view, then it is very unusual. Females of this species have a so-called brood chamber, which is securely protected by the edge of the shell and is located on the back. When favorable conditions are created around, the female lays 50-100 unfertilized eggs in this cavity, where they develop. Curiously, only females hatch from these eggs, leaving the chamber safely. Within a few days, the process repeats again, and young, grown-up and matured females will connect to this rapid breeding process. That is why in the summer, where Daphnia lives, the water seems to turn reddish. The pond is just teeming with this plankton. When the end of summer comes, the temperature of the air and water drops, males appear, which fertilize females, which give eggs with a denser shell. These fertilized eggs are called ephippia. Their distinctive feature is the ability to withstand winter frosts and drying up of water bodies, and they can be carried with dust. With the onset of spring and warmth, females hatch from them, and the life cycle repeats again.

Habitat

After we have learned what daphnia is, the habitat of these representatives of the planktonic genus should also become known to us, because for sure many of those who read this article are lovers of domestic fish and want to have such information. So, you can meet these tiny crustaceans in stagnant water bodies, for example, lakes, ponds, as well as water pits, ditches and even puddles. Often, places of their mass accumulation are excellent for self-harvesting of daphnia. It is quite easy to identify such a place: where daphnia lives, the water most often has a gray-green or reddish tint. Infusoria, bacteria, plant plankton become food for them.

Such different daphnia

Those who wish to catch daphnia on their own need to consider how sensitive they are to lighting. In bright light, crustaceans will try to go to the depths. There are different types of daphnia. The most common in the middle lane is the crustacean daphnia magna. The female individual reaches a length of 6 mm, but the male is only 2 mm. They usually live 110-150 days and in one clutch bring up to 80 eggs, which grow within 4-14 days. The smallest crustaceans reach only 1.5 mm in size and mature within a day, but they have litters every 1-2 days up to 53 eggs.

Why are they good for fish?

Why do lovers of aquarium fish try to be sure to feed them with daphnia? Everything is very simple. Regardless of whether they are fresh frozen or freshly caught, their stomach is usually full of plant foods, and this is so useful for aquarium fish that are deprived of a natural diet. That is why there must be daphnia in the aquarium. Despite the fact that the shell of daphnia is not digested, it serves as an excellent ballast substance. Thanks to him, the work of the intestines of the fish is activated, which is not able to fully move in the aquarium. For aquarium fish that have not yet grown up, representatives of the smallest daphnia, the moina, which has received the popular name "live-bearer", are simply ideal.

If you are planning to catch crustaceans on your own, you must take into account that where Daphnia lives, there is a consistent change in the size of the crustacean population. For fishing, a fabric net is used, the cells of which must correspond to the desired catch. Some experienced "fishermen" are advised to catch with a net with very small cells, and only then sort the feed by size through a sieve with different cells. You can engage in fishing, starting in spring and until a crust of ice appears on the pond. For such an event, a beach usually protected from the wind is chosen in calm weather in the morning or evening. Ideally, if the lighting is dim. Then Daphnia, whose habitat will thus become favorable, will rise to the upper layers.

Breeding daphnia at home is a fairly simple task, but it requires care and patience. For this, baker's yeast is usually used as food. You need to focus on the color of the water in the tank where you breed crustaceans. The water should be greenish or light brown. If you notice that its color becomes saturated, then in this case it is necessary to suspend the introduction of yeast for 1-2 days. The water should clear up again soon.

If breeding daphnia seems to you a very pleasant and interesting activity, be very careful and make sure that other inhabitants of the reservoirs do not get into the vessel along with the crustaceans, especially the cyclops. Get a magnifying glass and inspect the brood chambers of females every day. If they contain few eggs, then it is necessary to strengthen the diet. Daphnia, whose habitat at home is an aquarium or a temporary vessel of water, may also feed on dried nettle or lettuce leaves. They are first ground into powder, and then filtered through cheesecloth.

There is another simple way to breed daphnia at home. For this painstaking exercise, you will need a plastic or enamel bath, which must be half filled with water, and half-rotten hay and fallen leaves should be placed in it. Further, bacteria will begin to develop in this mass, which will become food for crustaceans. Sometimes, in order to provide additional nutrition to the bacteria, a small piece of yeast is added to the water (approximately 15 g per 1 m 3 of water). This should be done every two weeks as the water clears.

And now the most important point: daphnia, whose habitat is usually a natural reservoir, should get into your vessel with cooked food. To do this, about 50 crustaceans are caught in a stagnant reservoir for about 100 liters of water and poured into a prepared container.

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Most often, daphnia is found in stagnant water bodies - puddles, ponds, lakes, ditches, pits with water. Their mass quantity, suitable for self-harvesting, can be detected by coloring the water in red or gray-green. They feed on bacteria, ciliates and plant plankton, creating a stream of water with the help of the movement of antennas.

When catching daphnia on your own, you need to take into account that they react strongly to lighting. With a strong one, they will tend to go deep into the water, and with a weak one, up or towards the light source.

Daphnia magna - larva about 0.7 mm, males 2 mm, females up to 6 mm. Ripens in 4-14 days. Give up to 20 litters every 12-14 days. Clutch up to 80 eggs. Life expectancy - 120 - 150 days. Cerio daphnia reticulata - larva about 0.3 mm, males 0.5 - 0.8 mm, females up to 1.5 mm, mature in 2 - 3 days. Give up to 15 litters every 1 - 3 days. In laying up to 22 eggs.

Life expectancy - 30 days. Moina rectirostris - larva about 0.5 mm, males up to 1 mm, females up to 1.7 mm. They ripen in 3-4 days. Give up to 7 litters every 1 - 2 days. Clutch up to 53 eggs. Life span 22 days.

Optimum conditions: dH 6-18 o, pH 7.2-8.0, temperature - 20 - 24 o C, CO2 up to 8 mg / l, weak aeration, light 14-16 hours a day. Under conditions of artificial breeding, crustaceans tolerate mineral fertilizers well (for example, up to 5 mg/l of phosphorus salts). They are fed daily with chlorella (200 thousand cells / ml) or baker's yeast (2 ml of suspension per 1 liter of water). You can use horse manure: 1.5 g/l, adding another 0.8 g/l every 10 days. In nature, the food spectrum is wider - green algae (endorina, anzhistrodesmus, etc.), bacteria.

Daphnia - Species

In the middle lane, the following types of daphnia crustaceans are most common:
the largest daphnia magna - the size of the female is up to 6 mm, the male is up to 2 mm, the larva is 0.7 mm, grows within 4-14 days, the breeding interval is 12-14 days, in one clutch up to 80 eggs, lives 110-150 days;
crustaceans of medium size, daphnia pulex, female up to 3-4 mm, breeding period 3-5 days, clutch up to 25 eggs, lives 26-47 days.
small crustaceans, up to 1.5 mm: moina species, female up to 1.5 mm, male daphnia up to 1.1 mm, daphnia larva 0.5 mm, matures within a day, litters every 1-2 days, up to 7 litters , up to 53 eggs, lives 22 days.

The stomach of freshly caught or freshly frozen daphnia shrimp is usually full of plant foods, so they are useful for feeding aquarium fish deprived of their natural diet.

The shell of daphnia, which consists mainly of chitin, is not digested, but nevertheless serves as a valuable ballast substance that activates the work of the intestines of fish that are deprived of the opportunity to actively move in the aquarium. The smallest daphnia moina, which has the popular name daphnia “live-bearer”, is well suited for feeding grown-up juveniles of aquarium fish.

Only Daphnia magna, Daphnia pulex, Daphnia mion can be bred by amateurs. But they also need care, proper maintenance, nutrition. In this case, daphnia will fully reproduce and grow to become a quality food for fish.

Finding Daphnia for home maintenance is easy: you can buy or collect in a pond. Ponds with waterfowl, lakes with few or no fish (daphnia and diseases will be caught with fish), containers with settled water are good for catching. Prey at home is poured into a flat vessel, preferably white. So it is more convenient to filter the future feed again, because. foreign organisms will settle to the bottom or attach themselves to the white walls, where they are clearly visible.

If the collected crustaceans are used as food for fish, the water in which live food lives is not poured into common body of water. Daphnia is chosen with a net so as not to infect aquarium inhabitants. Daphnia Representatives of cladocerans are kept in a shaded place, tk. they do not tolerate light well. Normal water temperature for life is the range from 20 to 24 ° C (for the species Daphnia moin - 26-27 ° C), aeration is moderate to weak.

Plankton is fed: diluted baker's yeast, red meat water (meat juice, water washed off from it), chlorella. Yeast is frozen to a brownish color, 3 g is diluted in 1 liter of warm water. yeast; this is the standard proportion. Meat water give from 0.5 to 2 cm3 per liter of water. Instead of pure chlorella, you can simply add green aquarium water. In order for the fish to have high-quality food, horse manure and ammonium nitrate are added to food.

How to breed daphnia?

How to breed daphnia? For growing daphnia, a 15 liter plastic container, or any other, is perfect. In this case, several recommendations can be noted: 1. It is necessary to avoid the material of containers that are soluble in water and release harmful chemicals (some types of plastic, in particular, polypropylene);

2. If a metal container is used, it should not be made of stainless steel (some metals react slowly with water. Aluminum oxides form an oxide film, but some aluminum is released); 3. As in the case of a conventional aquarium, a large surface area with air is needed for gas exchange, because daphnia are very demanding on oxygen content;

4. If the container is located outdoors in strong sunlight or other lighting conditions, it is recommended to use more than 40 liter volumes so that the water environment is more stable. In addition, when black aquarium material is used, it heats up more than transparent or yellow, which must also be taken into account. For those who wish to have a small number of daphnia per week, the culture can be maintained in a two liter bottle.

For growing daphnia in an aquarium, it is a good idea to connect the lighting through a timer, which can be purchased at an electrical supply store. Daphnia magna has been found to prefer low aeration. In theory, aeration not only supports gas exchange, but also stabilizes water conditions and prevents crop inhibition.

daphnia pulex also likes low aeration. It is necessary to avoid small air bubbles that can get under the daphnia carapace, raise them to the surface, interfere with feeding and eventually lead to death (Artemia nauplii are also susceptible to this problem).

Catching

Catching Daphnia It all depends geographical location aquarist. The most common are Daphnia pulex and magna. For catching, it is necessary to choose lakes and ponds free from fish, because in the absence of the latter, more daphnia will be observed (in the absence of predators) and, in addition, the absence of pathogens is guaranteed.

If the aquarist intends to catch daphnia from natural waters, it is advisable to use a fine mesh net or sieve (homemade from muslin fabric). Sweep the net through the water evenly with movements in the shape of a figure eight, or slowly scoop it up. Too small net cells and too strong water pressure during catching should not be allowed, this can lead to the death of crustaceans.

Daphnia - Building

A little more about the structure of daphnia. This name is used by aquarists for various cladocerans. You can get an idea of ​​their appearance in the photo. In all representatives of daphnia, the body is strongly compressed from the sides and covered with a chitinous bivalve shell fastened on the back. There are two eyes on the head, which in mature individuals can merge into one compound eye, and in some species there may be another additional eye next to it.

Also on the head are two pairs of so-called antennae, the rear of which are large and additionally equipped with bristles that increase their area. It is due to the swing of these antennae that daphnia move in the water. When rowing with antennas, the body of the crustacean receives an abrupt forward movement, for which Daphnia received the second, popular, name “water flea”.

Daphnia reproduces quite unusually from a human point of view. Daphnia females have a cavity called a "brood chamber" located on their back and protected by the top edge of their shell. In the summer, if the conditions are favorable, unfertilized eggs are laid in this cavity, in the amount of 50-100 pieces. That is where they develop. Only females are hatched from them, which leave the chamber, and the adult female then molts.

A few days later, the process is repeated. Young female daphnia during this time also grow up and are connected to the breeding process. With a successful combination of circumstances, reproduction proceeds like an avalanche. That's where in the summer in small reservoirs daphnia often just teems, and the water seems to be colored reddish.

With a decrease in air temperature, at the end of summer and at the beginning of autumn, males begin to appear from some of the eggs, they fertilize the females and they have eggs enclosed in a dense shell. They are called ephippies. They are able to withstand drying and winter frosts, and can be carried with dust. Next spring, warmth and moisture will awaken them to life. The females will hatch and the cycle will repeat.

BREEDING IN HOME CONDITIONS.

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Daphnia

Daphnia are predominantly small crustaceans belonging to the Daphniidae family. This family, in turn, is included in Cladocera, which also includes gammaruses, brine shrimp, and others. For peculiar sharp movements, it is often called the "water flea". Not to mention the features of movement, daphnia also looks like a flea in appearance. However, the latter belongs to insects and has a very distant common ancestor with crustaceans, since both classes are included in the phylum Arthropoda. All types of daphnia have different variations, and sometimes representatives of the same species are very different from each other. Features of the phenotype, size and shape of the body depend on the area of ​​​​origin and specific environmental conditions. Representatives of the genus Moina have a significant similarity with Daphnia.

It is important to distinguish daphnia from other "water fleas" such as copepods, cyclops species, and barnacles, which often inhabit the same areas. Sharp movements, body shape and, to a lesser extent, coloration, are the best criteria for distinguishing without the need for examination under a microscope.

The genus Daphnia has a very wide distribution, including Antarctica, where Daphnia studeri, previously attributed to the genus Daphniopsis, was found in the relict salt lakes of the Vestfold oasis. At the beginning of the 20th century, the opinion about the cosmopolitan distribution of most species prevailed, but later it turned out that the faunas of different continents differ greatly. Some species, however, have very wide ranges and are distributed on several continents. The smallest number of species is characteristic of the equatorial regions, where daphnia are rare. The fauna of subtropics and temperate latitudes is the most diverse. In recent decades, the ranges of many species have changed due to their dispersal by humans. Thus, a species from the New World, D. ambigua, was introduced into Europe. In many reservoirs in the southern United States, D. lumholtzi has become common, which until then was found only in the Old World.

In ponds and puddles of central Russia, the following crustaceans of the genus Daphnia are often found, and therefore the most popular among aquarists. Daphnia magna (D. magna), female - up to 6 mm, male - up to 2 mm, newborns - 0.7 mm. Ripen within 10-14 days. Litters in 12-14 days. The clutch contains up to 80 eggs, but usually 20-30. The life expectancy of this crustacean is up to 3 months. Daphnia puleks (D. pulex), female - up to 3-4 mm, male - 1-2 mm. Litters in 3-5 days. In laying up to 25 eggs, but usually 10-12. Pulex live 26-47 days. In the lakes of the temperate zone of Eurasia, D. cucullata, D. galeata, D. cristata and several other species are often found.

Daphnia are small crustaceans, the body size of adults is from 0.6 to 6 mm. They inhabit all types of stagnant continental water bodies, and are also found in many slow-flowing rivers. In puddles, ponds and lakes, they often have a high abundance and biomass. Daphnia are typical planktonic crustaceans that spend most of their time in the water column. Various species inhabit shallow temporary water bodies, littoral and pelagial lakes. Quite a few species, especially those inhabiting arid regions, are halophiles living in brackish, saline and hypersaline continental water bodies. Such species include, for example, D. magna, D. atkinsoni, D. mediterranea, as well as most of the species previously assigned to the genus Daphniopsis.

Most of the time they spend in the water column, moving in sharp leaps due to the flapping of the second antennae, which are covered with special feathered bristles. Many daphnia are also able to slowly crawl along the bottom or walls of blood vessels due to water currents created by the pectoral legs; the antennae are motionless during this method of movement.

Perhaps the elusiveness of rapidly jumping crustaceans reminded scientists of the legend of the nymph Daphne, almost overtaken by Apollo, but never caught by him? Or maybe the mustache of the crustaceans seemed to someone like the branches of an evergreen laurel, into which a beautiful nymph has turned.

Ovid in his poem "Metamorphoses" told how one day the golden-haired god of light Apollo inadvertently laughed at Aphrodite's son Eros (or, as the Greeks also called him, Eros). The offended god of love from a golden bow struck the silver-faced patron of the muses in the very heart. Having once met the beautiful Daphne, daughter of the river god Peneus, Apollo fell in love with her at first sight, but the beautiful nymph, whom Eros struck with an arrow that kills love, started to run away from him with the speed of the wind. Then Apollo chased after her, but the nymph only ran faster and faster from the beautiful god. When her strength began to dry up, Daphne began to beg her father to deprive her of her appearance, which brought her only grief. Old Peney took pity on his daughter. And at that moment, when it seemed that Apollo had already caught up with the beauty, she turned into a laurel tree.

The saddened Apollo did not want to part with his beloved. He decorated his quiver and cithara with laurel leaves, and placed a wreath of laurel branches on his head, the aroma of which always reminded him of the elusive Daphne.

Reproduction in nature

During the summer months, daphnia are often found in flowering ponds and lakes that have a high concentration of algae. The fertility of Daphnia is simply amazing, which is associated with the implementation of parthenogenesis.

Parthenogenesis is the ability of self-reproduction without the need for fertilization, when the offspring completely repeats the parent's genotype, and any differences in the physiological state are determined by environmental conditions. Parthenogenesis allows daphnia to reproduce rapidly in favorable conditions, shortly after hatching from eggs. In nature, in late spring, summer and early autumn, depending on temperature, food availability and the presence of their metabolic products, daphnia reproduces parthenogenetically, giving rise to an average of 10 nauplii per adult. During this period, only females are present in the reservoir. The developing embryo is often visible inside the mother's body without a microscope. Females of the next generation are capable of parthenogenesis after 4 days of development, while childbirth occurs every three days. During her life cycle, a female may give birth 25 times, but in practice this number is slightly less and the female tends to produce no more than 100 offspring.

With a lack of food, some eggs develop into males, and females begin to produce eggs that must be fertilized. The latter develop into small embryos which then hibernate, covered with a dark brown/black saddle shell known as the ephippium. In this form, daphnia can tolerate harsh environmental conditions, short-term drying of the reservoir and even its freezing. Females born to form ephippium are easily distinguished from parthenogenetic individuals because the developing ephippium is present as a black spot at the posterior end of the body. When environmental conditions become favorable again, a generation appears from the eggs, which, in turn, gives birth only to females, while all males die before the onset of unfavorable conditions.

Fishing in natural waters

They catch daphnia with a net. A special net is needed for this - with a long handle up to 2-3 meters, usually made up of several screwed segments, about 25-30 cm in diameter and a fabric cone about 50-60 cm long with a rounded end. The net ring is made of durable material, such as stainless steel wire with a diameter of 3-5mm. If you make it thinner, it will bend easily, and taking into account possible snags at the bottom ... But the most difficult thing is to choose a fabric for the net. Here, synthetic materials are preferable, such as nylon, which do not rot from prolonged contact with water. The size of the net mesh depends on what you are going to catch, a very small fabric greatly slows down the net in the water, so it is better to have several interchangeable rings with different fabrics for catching food of different sizes.

The net works calmly, smoothly, without much effort leading it with the “eight” in places where daphnia accumulate. We spent a couple of times, took it out, shook out the catch, and began to fish further. If you push a full net, then many daphnia crumple and die, so it is better to take it out more often with small portions of prey. And then greed, you know, does not lead to good. For fishing, it is better to prefer smaller reservoirs, for example, the same puddles - there daphnia are more accustomed to oxygen starvation and will more easily endure further transportation. True, it is difficult to catch with a typical net in small puddles, there you have to use a net with a shorter cone - otherwise it starts to cling to the bottom and understand the turbidity. In order not to catch hydra with daphnia, one should try to catch prey away from thickets of aquatic plants or objects in the water to which it can be attached. And in no case is it recommended to catch food in reservoirs where fish live - with such food it is easy to introduce pathogens of various diseases.

Captured daphnia are placed in a container - a can or a special cann for transportation. It is advisable to strain the catch through a sparse mesh before pouring to remove any debris and any large unwanted guests - swimming beetles or large dragonfly larvae. It is highly desirable to have a battery-powered compressor in the transport tank - it will keep most of the catch alive during the journey home.

Houses of captured daphnia are poured into a wide flat vessel, such as a white enameled basin. There, for some time, all unwanted organisms settle on the bottom and walls, on a white background it is easy to detect dragonfly and leech larvae, and everything else that has nothing to do with daphnia. In the same place, dead crustaceans accumulate at the bottom. When feeding, daphnia are caught with a net, the water in which they are located cannot be poured into the aquarium! These crustaceans are best suited for feeding small aquarium fish such as guppies or neons. For larger fish, it is more convenient to use live or frozen bloodworms.

In nature, daphnia live in ponds and large puddles, where they feed on various bacteria and phytoplankton. However, such water bodies are often polluted with industrial waste or fish are found in them. Both can lead to diseases in aquarium inhabitants.

Daphnia can also be dangerous for the aquarists themselves. In spring and early summer, the diet of crustaceans often includes pollen from flowering plants, carried by the wind into water bodies. Daphnia caught at this time and dried for future use when feeding fish can cause a painful reaction in people suffering from pollen allergies. This fact, in particular, can explain the often encountered opinion that the aquarium is harmful to health. In fact, the reason is pollen, which during the period of mass flowering of grasses is literally “stuffed” with crustaceans.

Breeding at home

For growing daphnia, a 15 liter plastic container, or any other, is perfect. In this case, several recommendations can be noted. Avoid container material that is water soluble or releases harmful chemicals. If a metal container is used, it must be made of stainless steel. Aluminum oxides form a film, but some aluminum is still released. As in the case of a conventional aquarium, a large area of ​​​​contact with air is necessary for gas exchange, because daphnia are very demanding on the oxygen content. If the container is located outdoors, in strong sunlight or other lighting, it is recommended to use more than 40 liter volumes so that the water environment is stable. In addition, when black pond material is used, it heats up more than transparent or yellow, which should also be taken into account.

For those who wish to have a small number of daphnia per week, the culture can be maintained in a two liter bottle. For growing in an aquarium, it is a good idea to connect the lighting through a timer, which can be purchased at an electrical appliance store. Daphnia magna has been found to prefer low aeration. In theory, aeration not only supports gas exchange, but also stabilizes water conditions and prevents crop inhibition. Daphnia pulex also likes low aeration. It is necessary to avoid small air bubbles that can get under the daphnia carapace, raise them to the surface, interfere with feeding and eventually lead to death.

The best nutrient medium for the culture are blue-green algae. They are usually free-floating green algae that tend to turn water into "pea soup", yeast (Sacromyces spp and similar fungi) and bacteria. The combination of the above objects makes the culture maintenance process successful, yeast and algae complement each other.

Microalgae are consumed by daphnia in huge quantities, and an abundance of crustaceans is observed in places where water bodies bloom. There are a number of ways to ensure the development of algae that require minimal effort.

Placing the culture container in direct sunlight guarantees algae development within two weeks, usually earlier. Their spores are airborne and colonize water bodies, but, as a rule, some algae is added to the water to speed up flowering. Use of plant fertilizers, such as Miracle grow. Once a week, 1 teaspoon of fertilizer is added to a 4 liter container. The container must be placed in direct sunlight. Aeration and slow movement of water is necessary. A system should be built whereby the first container of algae is already green, the second will acquire this shade within two days, the third within two more days, etc. When the first container becomes light green (after 2 weeks), it is poured into the culture of daphnia. The empty container is refilled with the mixture with the addition of a small amount of water from the second container. Thus, every two days the aquarist has 4 liters of blooming water ready to be fed to the daphnia.

The advantages of algae are the ease of preparation and the extremely rapid development of the culture of daphnia that consume them. There are no disadvantages, except for the need to constantly restart the tanks. Daphnia should not be placed in an environment that is too rich in algae, because algae tend to raise the pH up to 9. High alkalinity is associated with an increase in ammonia toxicity, even at low concentrations.

Bakers', brewers', and virtually all other types of yeast are suitable for daphnia cultivation, but it is recommended that no more than 28 g per 20 liters of water be used daily. In the case of using yeast, algae can be added to the water, which will prevent environmental pollution. It is important not to overdo it with the addition of yeast, excess will pollute the environment and destroy the daphnia culture.

Some baker's yeasts are mixed with active ingredients such as calcium sulfate, ascorbic acid, which promote the development of fungi. These components themselves are harmless to the culture, however, ascorbic acid can lower the pH of the medium to 6, which is far from ideal for Daphnia. This usually happens with overfeeding.

The advantage of yeast as a nutrient medium is that it is easy to obtain and requires minimal effort to prepare and maintain the culture. However, they are not as valuable in terms of nutrition for daphnia as algae. Crustaceans need to consume more yeast than algae to obtain the same nutritional value.

Daphnia lives in a wide range of temperatures. The optimum temperature is 18-22 C. D. pulex thrives at temperatures above 10 0C. Moina withstands even more severe fluctuations, 5-31 C; the optimum is 24-31 C. The increased resistance of Moina to temperature indicators makes it a preferred object of cultivation, when for D. magna in natural conditions the optimum is reached only once a year.

Daphnia are tolerant of dirty water, and dissolved oxygen levels can range from near zero to supersaturated. Like brine shrimp, the ability of daphnia to survive in an oxygen-poor environment is due to the ability to form hemoglobin. Hemoglobin production can be accelerated by increasing temperature and population density. As well as in the case of Artemia, Daphnia does not tolerate active aeration with small air bubbles that can kill it.

Daphnia production is a relatively easy process. However, there are measures to increase the productivity of cultivation. Good aeration, good to the extent that the water is oxygenated, but not overly aerated, is a major factor in increasing productivity. Some species prefer no aeration, but Daphnia magna is best bred in its presence. In addition, this allows you to increase the density of the culture, the circulation of water reduces algal plaque on the walls of the vessel, and also transfers food particles to a suspended state, which is typical for the natural diet of daphnia. The only drawback is that small air bubbles fill the carapace of crustaceans, which float up and cannot feed. Air atomizer should be avoided altogether, or it should be very coarse to create large bubbles. Convenient in terms of aeration is the "bio-foam" filter. It is usually used in a fry tank but is ideal for Daphnia. It captures large particles and promotes their decomposition to feed the algae.

Regular selection/collection of culture. This event maintains a constant increase in culture and provides daphnia with the opportunity to accumulate oxygen and food faster. 24-hour daylight hours increase the productivity of daphnia, but this is an optional measure. Also, do not keep Daphnia in the dark for 24 hours, because this stimulates the crustaceans to form ephippia. The mode and degree of water replacement depends on the nutrient medium used, but, in any case, they are necessary for purification from metabolites and toxins.

When it comes to cultivating Daphnia, harvesting it can be a real challenge, but it is an integral part of the whole breeding process. Otherwise, overpopulation becomes a serious problem. Even if you have to shake out the crustaceans in the sink, this must be done, because the culture can become unstable. If the aquarist cultivates daphnia at temperatures below 25 0C, it makes sense to start catching in the middle of the second week. This is because most crops take several days to adapt and start reproducing. When culling / trapping, a net is used that has meshes large enough to pass young crustaceans, but small enough to catch adults. Some aquarists recommend pouring ¼ of the container through the net and then refilling the volume with fresh water and culture medium. No more than ¼ of the population can be caught daily, which also depends on the quality of cultivation. Catching can be done during the day when aeration stops, when all daphnia rise to the upper layer of water.

Caught crustaceans can live for several days in a jig with fresh water. They exhibit normal activity at elevated temperatures. However, the nutritional value of daphnia gradually decreases because they are starving and for the best effect it is necessary to provide them with food. For a long time, crustaceans can be stored frozen if they are frozen in water with a low salt content (0.007 ‰, density - 1.0046). Of course, this will kill the daphnia, by washing out the nutrients, their value will decrease, almost all enzymatic activity will be lost within 10 minutes, and after an hour ½ of the free amino acids and all related ones will be lost. Fish are not so willing to eat frozen crustaceans.

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