Daphnia habitat. Water flea: features of the life activity of Daphnia. Buy Daphnia moina eggs

WHO IS DAPHNEIA? HABITAT

Daphnia (lat. Daphnia) is a genus of planktonic crustaceans from the superorder Cladocera. Body length - from 0.2 to 6 mm. Daphnia are sometimes called water fleas. Daphnia are small crustaceans (body sizes of adults range from 0.2 to 6 mm). They inhabit all types of standing continental water bodies, and are also found in many rivers with slow flow. In puddles, ponds and lakes they often have high numbers and biomass. Daphnia are typical planktonic crustaceans, spending most of their time in the water column. Various species inhabit shallow temporary reservoirs. littoral and pelagic zones of lakes. Quite a few species, especially those inhabiting arid areas, are halophiles, living in brackish, saline and hypersaline continental water bodies. These species include, for example, D. magna, D. atkinsoni, D.mediterranea, as well as most species previously classified in the genus Daphniopsis. They move 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 applied to all cladocerans). Many daphnia are also capable of slowly crawling along the bottom or walls of vessels due to water currents created by the thoracic legs (the antennae are motionless with this method of movement).
Spreading Genus Daphnia has a worldwide distribution (including Antarctica, where Daphnia studeri, previously assigned to the genus Daphniopsis, was discovered in the relict salt lakes of the Vestfold Hills oasis). At the beginning of the 20th century, the prevailing opinion was that most species had a cosmopolitan distribution, but it later became clear 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 typical for equatorial regions, where daphnia are rare. The most diverse fauna is in the subtropics and temperate latitudes. In recent decades, the ranges of many species have changed due to human dispersal. Thus, a species from the New World, D. ambigua, was introduced into Europe (England). In many reservoirs in the southern United States, D. lumholtzi, which was previously found only in the Old World, has become common.


Taxonomy One of the largest (more than 50 valid species in the world fauna) and difficult for taxonomy of the cladoceran genera. Type species - D. longispina O.F. Mueller, 1785. Most characteristic hallmark genus - antennae of females fused with the head. In addition, females usually have a well-developed rostrum, 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 spine. Most species (except some Australian species, often classified in the genus Daphniopsis) have two eggs in the ephippium. All setae of antenna II are 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 the subgenus Daphnia (Daphnia) there is no notch for the head shield; the egg chambers of the ephippium are usually almost perpendicular to the dorsal margin of the valves. Representatives of the subgenus Daphnia (Ctenodaphnia) have a notch for the head shield, and the egg chambers of the ephippium are usually almost parallel to the dorsal margin of the valves. All species previously assigned to the genus Daphniopsis are included in the subgenus Daphnia (Ctenodaphnia), and many of them have primitive (no notch of the head shield) or evasive (one egg in the ephippium) characters.

STRUCTURE OF DAPHNIA

Internal structure

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 suprapharyngeal 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 suprapharyngeal ganglion proper. The optic nerve arises from the anterior part of the optic ganglion and connects the brain to the compound eye. The unpaired compound eye in Daphnia is formed from a paired rudiment (embryos have two eyes) and contains exactly 22 facets (ommatidium). It is located in a special cavity inside the head, to the walls of which it is suspended by two ligaments (ligaments) and driven by three pairs of extraocular muscles. In living individuals, tremor of the eye is noticeable, and from time to time larger jumps (saccades) of the eye are observed. Nerves also extend 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. Adjacent to the lower part of the suprapharyngeal ganglion is the simple eye (ocelli, nauplial eye). In most species it contains pigment and is visible as a small blackhead. There are 4 groups of sensitive cells around the pigment spot. Daphnia has a complex system striated muscles that move the second antennae, post-abdomen and thoracic 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 the oral opening, which is covered by a large upper lip. Giant highly polyploid cells located inside the lip secrete a secretion that glues food into a food bolus. Through the movements of the mandibles, it is transported into 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 post-abdomen. Inside the head, two curved liver processes extend from the midgut. In the posterior part of the post-abdomen there 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 the ostia - two slit-like side 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 ensured by transparent partitions between different parts of the myxocoel. Breathing occurs through the integument of the body, primarily the thoracic legs, on which there are respiratory appendages - epipodites. The latter also take part in osmoregulation. An additional organ of osmoregulation in newborns is the large nuchal 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 (testes in males) are located on the sides of the intestines. At the posterior end there is a breeding zone for oogonia; the rest of the ovary is filled with maturing oocytes. As the eggs mature, they move to their posterior third, where there are narrow oviducts that open into the brood chamber. In males, the vas deferens open on the postabdomen in its distal part, and in many species on special papillae.

External structure Unless otherwise stated, this section describes the anatomy of females. The integument consists of a head shield and a bivalve carapace. They usually have a clearly visible 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 at the posterior end there is a tail spine covered with spines. Many species have a row of feathered setae on the inner edge of the valves in its middle part; males of all species have the same setae and additional setae on the anterior-inferior corner of the valves. On the head, most species have a beak-shaped outgrowth, the rostrum. Below it are located the first antennae (antennales) - short projections bearing at the end 9 olfactory setae - aesthetascus (aesthetascus), and on the lateral surface - one additional seta. In males, the first antennae are larger, more mobile, and, in addition to aesthetascae, bear a large seta (“flagellum”) at the distal end. On the lateral surface of the head there are projections 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 fornix, second antennae (antennae) are attached to the head by 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 setae covered with flattened hairs, forming “oars” when swimming. There are five of them on the three-segmented branch (four only in D. cristata), and four on the four-segmented branch. There are several small sensitive bristles on the base. From back surface a large upper lip comes off the head. Inside it there are several giant polyploid cells that secrete a secretion that glues the 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 chitinized chewing surfaces covered with ridges and outgrowths. During feeding, the mandibles transport food into the mouth opening. Under the carapace there are small maxillae 1 (maxillulae), bearing four setae. The second maxillae in Daphnia are reduced. There are five pairs of two-branched thoracic legs of complex structure. The legs of the first and partly the second pair differ in structure in males and females. On the first pair of legs of males there are hook-shaped projections that allow them to cling to females during mating. The third and fourth pairs carry fans of filter bristles. On each leg there is a respiratory appendage - an epipodite. Behind the thoracic region there is a reduced abdominal region, the presence of which is “marked” by dorsal abdominal processes that cover 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 there are two rows of denticles, between which is the anus. In males of some species these denticles 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 furcae, according to others, they are a pair of large modified setae. There are spines on the outer and inside claws, usually there are three groups of spines on the outer side, and two on the inner side. The post-domain serves to clean the filtration apparatus from large foreign particles.

CHANGES IN THE BODY SHAPE OF DAPHNIAS AT DIFFERENT SEASONS OF THE YEAR

Many species of daphnia (mainly 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 spine and a head shield. In spring and autumn generations, the tail spine is shorter, the helmet may be shorter or absent altogether. It has been shown that growing outgrowths requires energy expenditure and leads to a decrease in fertility. Of the factors causing the growth of outgrowths of the integument, 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 different types of invertebrate and vertebrate predators. Many hypotheses have been put forward about the adaptive role of cyclomorphosis: easier soaring in less dense and viscous water, accelerated swimming in the horizontal direction, etc. Most of them are either unproven or refuted. Nowadays, the theory about the role of outgrowths in protection from predators is accepted as the main explanation for cyclomorphosis. Transparent outgrowths increase the actual size of the body and thereby protect from small invertebrate predators - more big catch with outgrowths it is more difficult to grab and not release when manipulating - “pushing into the mouth.” Sometimes the tail spine breaks off, which can play the same role as autotomy of the tail in a lizard. At the same time, the transparent outgrowths do not increase the apparent size, which is important for protection from large visual predators - fish.

MOLTING

When molting, the cervical suture—the line between the head shield and the carapace—diverges, and the animal emerges from the exuvium. Together with the carapace, the integument of the body and limbs is shed. Molting occurs periodically throughout the life of the individual. Typically, molting occurs in the water column; ephippial females of some species molt, sticking from below to the surface film of the water. Several molts occur during embryonic development, in the brood chamber.

WHAT AND HOW DOES DAPHNIA EAT?

The main food for daphnia are bacteria and unicellular algae. Species that survive the winter in an active state (in deep, non-freezing reservoirs) spend it in the bottom layers of water, feeding mainly detritus (organic remains). They feed by filtration, creating currents of water with rhythmic movements of the chest legs. Food is filtered by fans of filtering setae, which are located on the endopodites of the III and IV pairs of thoracic legs. Large particles stuck in the filtration apparatus (for example, filamentous algae) are removed using the postabdomen and its claws. From the filtering 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 with a large upper lip, inside which there are salivary glands from giant polyploid cells. Their secretion glues food particles together into a food bolus. At an average concentration of food in water, adult daphnia of various species are filtered at a rate of 1 to 10 ml/day. The daily food intake of an adult D. magna can reach 600% of its body weight.

HOW DOES DAPHNIA BREATHE?

On the thoracic legs there are sac-like respiratory appendages - gills. Probably, a significant part of the oxygen of daphnia is obtained through the thin integument of the body and limbs, and the respiratory appendages, like the occipital organ of newborns, play important role in osmoregulation. Some species (for example, D. pulex, D. magna), with a low oxygen content in the water, begin to synthesize hemoglobin, so that their hemolymph and the entire body turn red.

MIGRATION OF DAPHNIAS IN A RESERVOIR

Like other representatives of zooplankton, daphnia make vertical migrations in many bodies of water - 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 that explain the causes of migrations, on which a significant percentage of energy is spent, the theory that connects migrations with the same protection from predators is now considered the most substantiated. During daylight hours, larger species, clearly 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 Daphnia species can be well expressed in lakes where there are many fish, and absent in lakes where planktivorous fish are absent.

DAPHNIA REPRODUCTION AND DISPERSAL

Most daphnia (like other cladocerans) are characterized by cyclic parthenogenesis. In favorable conditions (for example, in summer in non-drying puddles and shallow reservoirs), 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 - the offspring of individual females). The development of embryos during parthenogenesis occurs in the brood chamber under the shell and is accompanied by several molts. Then the young crustaceans emerge from the brood chamber (direct development). In the fall 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 bodies of water usually requires exposure to two stimuli: a decrease in temperature and a decrease in length. daylight hours. It is hypothesized that these and other stimuli act by reducing the female's food intake. Male daphnia are smaller in size and differ significantly from females in the structure of the first antennae and thoracic legs. They swim faster than females and mate with them, attaching themselves to the rear 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 farnesoate, a juvenile hormone of crustaceans, to the medium, as well as analogs of the juvenile hormone of insects—the insecticide fenoxycarb. 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 to develop. After fertilization, they also exit into the brood chamber, the covers of which thicken and form a special chitinous chamber - the ephippium (ephippium). Most Daphnia species have two eggs in the ephippium; in some Australian species, often isolated in separate genus Daphniopsis, ephippium has one egg. In species of the subgenus Daphnia, the long axes of the eggs are perpendicular to the dorsal edge of the ephippium; in species of the subgenus Ctenodaphnia, they are parallel to it or inclined at a slight angle. Egg development continues until the gastrula stage, then they enter suspended animation. 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 effipium, females of some species (for example, D. pulex) often die. Together with ephippiums, daphnia eggs are carried by the wind, spreading 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 taking off from the surface of the water and be carried by them, and more often smooth ephippiums are carried by smaller ephippiums. Eggs in a chemically resistant shell inside the ephippium 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 toxic salts (for example, mercuric chloride HgCl2) at a concentration of poisons thousands of times higher than the maximum permissible concentration; after the egg shell ruptures, the hatched embryos in such solutions immediately die.

BREEDING DAPHNIAS

Cultivation of Daphnia as food is widespread, as in industrial purposes, and by amateur aquarists. In favorable conditions, daphnia reproduce 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 source culture can easily be obtained from natural reservoirs. It is advisable to catch crustaceans in small bodies of water, where the daphnia population can be practically free from the admixture of other animals. IN winter time A culture of daphnia can be obtained from ephippial resting eggs, previously collected 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 optimal density of the crop is 300-1000 g/m³. Periodically, every few weeks or months, the culture is replanted. The aging of a crop is associated with the accumulation of metabolic and decomposition products in it and with its contamination by other organisms. When changing water, the life of the crop is extended. The optimal growing temperature is 15–25°C, the reaction of the medium is neutral (pH 6.8–7.8), the oxygen content is at least 3–6 mg/l, the oxidability is 14.8–26.2 mg O2/l. When growing daphnia, both joint and separate cultivation of crustaceans and food for them are used. When grown together, organic fertilizers are added to the crop, for example, manure applied in an amount of 1.5 kg/m3. It is possible to grow on mineral fertilizers, the addition of which causes the rapid development of unicellular algae. The disadvantages of co-cultivation are severe water pollution, rapid aging of the culture and rapid overgrowing of the container with filamentous algae. Separate cultivation of daphnia and food for them does not have these disadvantages, but is technically more complex and is used mainly in conditions of mass industrial cultivation of feed crustaceans. In this case, an algal culture is grown separately, which is added to the container with daphnia 1-2 times a day. Breeding In laboratory and home conditions, it is convenient to maintain a culture of daphnia with yeast, added daily little by little in the amount of 15-20 g per cubic meter of culture (15-20 mg/l). Standardized methods for laboratory cultivation of Daphnia are described in toxicology and bioassay manuals.

Daphnia species that are often cultivated

In ponds and puddles middle zone In Russia, the following crustaceans of the genus Daphnia 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. They ripen within 10-14 days. Litters in 12-14 days. There are up to 80 eggs in a clutch (usually 20-30). Life expectancy is up to 3 months. Daphnia pulex (D. pulex), female - up to 3-4 mm, male - 1-2 mm. Litters in 3-5 days. There are up to 25 eggs in a clutch (usually 10-12). They 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.

Genus: Daphnia = Daphnia

Daphnia - general " popular name» all species of Cladocera (CLADOCERA). Under this name there are about 420 different species of cladocera, belonging to about 10 families. The most common are: Daphnia magna, Daphnia pulex, Daphnia longispina, Moina, Bosmina, Hidorus, Sida, Simocephalus, Ceriodaphnia. The body of most cladocerans is strongly compressed laterally and enclosed in a bicuspid chitinous shell, fastened on the back and diverging on the ventral side. Daphnia periodically sheds this shell and replaces it with a new one. The front of the daphnia's head is elongated into a sharp "beak" or "proboscis." There are two eyes on the head, which in fully developed specimens merge into one compound eye. In many species there is another small eye next to it.

There are two pairs of antennas on the head. The anterior antennae are rod-shaped and very small. But the rear antennae are disproportionately large compared to the body. They are branched, and each branch of the antenna is equipped with long feathery bristles. The rear antennae serve as the main organ of locomotion for cladocerans; simultaneously flapping both rear antennae, the crustaceans are pushed off by them and thus swim in short leaps. By adjusting the frequency of antenna flapping, daphnia can not only “hover”, but also rise to the upper layers of water or, conversely, go to depth. Thus, they make vertical movements (migrations) associated with the search for food, changes in water temperature or time of day. The thoracic region of cladocerans is shortened and consists of 4 - 6 segments, each of which is equipped with a pair of legs. In females, between the dorsal surface of the body and the dorsal edge of the shell there is a large cavity that serves as a brood chamber. Eggs are laid in this bag, where they develop.

In summer, in warm weather, unfertilized eggs are formed in the female’s brood chamber (50-100 eggs for each individual), from which only females emerge and very quickly leave the mother’s body. Therefore, as a rule, all daphnia caught in the summer turn out to be females. Throughout the summer, females reproduce parthenogenetically. With the onset of cold weather, males are born from some eggs, and females begin to form eggs, which can develop only after fertilization by a male. Males of daphnia are rare, usually appear in the fall and are always much smaller than females. After they fertilize the females, eggs are formed (usually no more than two), rich in yolk and completely opaque. The shell containing the eggs forms a saddle, or ephippium. Ephippia swim freely or sink to the bottom, they tolerate freezing and drying. Dried ephippias are carried by the wind. Warmth and moisture awaken the eggs to life; from them females are hatched, capable of reproducing virginally for many generations. The coloring of daphnia depends on the composition of the food consumed and the oxygen content in the water of the reservoir. Color varies from green and brown to red and black. Cladocerans feed on unicellular algae, bacteria and ciliates, which they draw into their mouths with a current of water created by the movement of their legs. Typically, in nature there is a sharp increase in the number of daphnia following the death of phytoplankton.

Cladocerans are present in almost every body of water. But greatest number Daphnia is found in stagnant waters (ponds, lakes, ditches, water holes) rich in decaying plant organic matter with a small population of fish. The peak of the maximum number of daphnia in water bodies occurs in spring and summer. Sometimes there are so many of them that the water turns red-brown from their quantity.

Most major representative genus Daphnia magna (Daphnia magna Straus). Lives in small bodies of water (ponds, pits, forest puddles). Females reach 5 - 6 mm in length, males - 2 mm, larvae - about 0.7 mm. They ripen at the age of 4 - 14 days. They produce up to 20 litters every 12 - 14 days. There are up to 80 eggs in a clutch. Life expectancy is 110 - 150 days. Daphnia pulex De Geer is widespread in shallow water bodies. crustaceans average size, their size is up to 4mm; They produce up to 12 litters every 3 - 5 days. Each clutch contains up to 25 eggs. Life expectancy is 26 - 47 days.

Daphnia longispina Muller their size is up to 4 mm. Lives in both shallow and deep reservoirs. Has a number of different forms.

Simoctphalus are flat crustaceans, often colored red. Habitat: shallow ponds with standing water. Their body length ranges from 2 to 4 mm.

Ceriodaphnia is similar in shape and size to previous species. The habitat is the same.

Moina - “live-bearer” – (Moina macrocopa, M. rectirostris). Females reach a length of up to 1.7 mm, males - up to 1 mm, larvae - about 0.5 mm. They ripen in 3 - 4 days. They produce up to 7 litters every 1 - 2 days. There are up to 53 eggs in a clutch. Life expectancy is 22 days. Moina as a food item has a number of advantages over other species of daphnia. The size of an adult moina rarely exceeds 1 mm, which makes it possible to use it when feeding fry, while the size of other species of daphnia reaches 4 mm. The chitinous shell of moina is much softer. Juveniles of various species aquarium fish When fed with moina, it grows much faster and reaches puberty earlier than when fed with other types of food. Biochemical analysis showed that the nutritional value of Moina macrocopa is 20% higher than Daphnia magna. Moina's body contains more than 50% protein. Its reproduction rate is approximately three times higher than that of Daphnia pulex.

Bosmina is one of the smallest representatives of cladocerans with long beak-like appendages on the head. Bosminas are often caught when fishing for daphnia - they are very similar to them, but twice as small. These black crustaceans are found in large numbers along the coast and in clusters aquatic plants.

Chydorus are small crustaceans, characterized by their round shape and small size. Cladocera (Cladocera) is one of the best aquarium foods for small fish species, as well as juveniles of almost all species. Fish eat them willingly, with appetite, and grow on them much better than on many other types of food.

Some species of Daphnia are specially cultivated in fish farms as highly valuable food for young fish. Daphnia are one of the most complete aquarium foods in terms of composition. High protein content, a large number of trace elements and vitamins, optimal amino acid composition of protein - all this makes daphnia a very popular food for aquarium fish among aquarists all over the world.

Hello to all aquarists! In this publication I will tell you about live food for Daphnia fish. There are several species of daphnia, but Daphnia moina or magna are bred at home as these species are better suited for breeding than others.

Many aquarists raise their own live food. Such food can be: acetic eel and panagrel, grindal and enchytraeus, aulophorus, and even Drosophila flies. I breed Daphnia moina for my fish, and I think this is the best live food.

For those aquarists who are not familiar enough with the Daphnia crustaceans, I can suggest that they familiarize themselves in more detail with the Wikipedia material. Daphnia (lat. Daphnia) - a genus of planktonic crustaceans from the superorder Cladocera ( Cladocera). Body length - from 0.2 to 6 mm. Daphnia are sometimes called water fleas.

Cultivation of daphnia as food is widespread, both for industrial purposes and by aquarists. In favorable conditions, daphnia reproduce 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 source culture can easily be obtained from natural reservoirs. It is advisable to catch crustaceans in small bodies of water, where the daphnia population can be practically free from the admixture of other animals. In winter, a culture of daphnia can be obtained from ephippial resting eggs, previously collected 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 optimal density of the crop is 300-1000 g/m³. Periodically, every few weeks or months, the culture is replanted. The aging of a crop is associated with the accumulation of metabolic and decomposition products in it and with its contamination by other organisms. When changing water, the life of the crop is extended.

The optimal growing temperature is 26-29°C, the medium reaction is neutral (pH 6.8-7.8), oxygen content is at least 3-6 mg/l, oxidability is 14.8-26.2 mg O 2 /l. When growing daphnia, both joint and separate cultivation of crustaceans and food for them are used.

When grown together, organic fertilizers are added to the crop, for example, manure applied in an amount of 1.5 kg/m3. It is possible to grow on mineral fertilizers, the addition of which causes the rapid development of unicellular algae. The disadvantages of co-cultivation are severe water pollution, rapid aging of the culture and rapid overgrowing of the container with filamentous algae.

Separate cultivation of daphnia and food for them does not have these disadvantages, but is technically more complex and is used mainly in conditions of mass industrial cultivation of feed crustaceans. In this case, an algal culture is grown separately, which is added to the container with daphnia 1-2 times a day.

In laboratory and home conditions, it is convenient to maintain a culture of daphnia with yeast, added daily little by little in the amount of 15-20 g per cubic meter of culture (15-20 mg/l). Standardized methods for laboratory cultivation of Daphnia are described in toxicology and bioassay manuals.

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

Daphnia is one of the objects for testing the toxicity of aqueous solutions chemical compounds, used in the study of water 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 the movements of the crustaceans to slow down; they either sink to the bottom or freeze at the surface film of water.

Why is Daphnia moina better?

This species of daphnia is unpretentious and reproduces quickly, and it contains more protein than other species of daphnia. Daphnia moina is not only smaller, but also softer and can be used not only as food for adult fish, but also as a live starter food for fry, which is very important when breeding fish.

In addition, this starter food is planktonic and corresponds to natural fry food. For aquarists and fish breeders, this food is a real find.

In fact, Daphnia moina is a universal food, and its versatility lies in the fact that large crustaceans are suitable for feeding adult fish, and small fry, which are always present in large quantities in the aquarium, are suitable for feeding fry. For example, when I bred fire barbs, I added daphnia directly to the fry in the aquarium. Daphnia lived and multiplied, and the fry, eating small crustaceans, grew very quickly.

It must be said that aquarists come to live food when they start breeding fish for the simple reason that adult fish can survive on dry food, but it is usually not possible to raise fry without live food.

But not only fry, but also adult fish need live food, so if your fish’s diet consists of live food, this will have a very beneficial effect on their health and well-being. Fish that eat live food get sick less and do not lag behind in growth.

Such fish willingly go to spawn, and spawning can occur without any preparation and even in a community aquarium. Live food has a calming effect on new fish when the fish are still at the stage of stress and adaptation, and for sick fish this is perhaps the only food that they do not refuse.

Daphnia moina breeding at home

I breed daphnia in a fifty-liter aquarium, which is lit with one 20-watt fluorescent lamp. The duration of daylight is 8-12 hours, and the water temperature ranges from 26 to 28° degrees. You need to know that the higher the water temperature and the longer the daylight hours, the faster the daphnia reproduces and vice versa.

I feed daphnia with dry baker's yeast after dissolving it in water and adding it to the aquarium until the water becomes slightly cloudy. When the water becomes clear again, I repeat feeding. I use aeration in rare cases, for example, when it is necessary to remove a film from the surface of the water or to mix the yeast more thoroughly.

It is best to start breeding daphnia in a small container, for example, it could be a liter or one and a half liter glass jar. Why should the initial dishes be small? The fact is that for a small number of crustaceans in large volume More water and yeast will be needed, and yeast eaten by crustaceans at the wrong time may precipitate.

Of course, there is nothing particularly scary here, but it is better to maintain cleanliness since daphnia always feel better in fresh water. The water in the jar should be from a healthy aquarium, in which medications have not been used before or have not been used for a long time, and if such water is not available, you can simply get by with tap water, but only without chlorine in it.

Breeding Daphnia moina is easy and simple; in fact, let me tell you and show you how it’s done. I have in my hand a bag containing a breeding of Daphnia moin, it consists of a mixture of river sand and ephippia.

Daphnia eggs

Ephippia are the eggs of daphnia. They look like small white grains that crustaceans carry on their backs and periodically drop, then from the ephippia new daphnia are born, by the way, the same small fry that are excellent as starter food for fry of many species of fish.

Ephippia can be seen at the bottom of a cultivator's aquarium or floating in a net when catching daphnia. You can find out how to get daphnia breeding in a registered letter on my blog from the publication “Daphnia fish food”.

It must be said that such a distribution was invented by me to distribute it to the northern geographical areas where daphnia is not found at all, but as statistics show, all aquarists and even aquarists from neighboring countries need this live food.

Pour the mixture into the jar and carefully stir it so that the sand is evenly distributed along the bottom of the jar. We leave the jar in a lighted place, for example, a windowsill, and wait. On the second or third day, depending on the water temperature, daphnia will be born.

Well, a day passed and on the second day daphnia crustaceans appeared. Let's start feeding.

It is necessary to wait 3 to 5 days for a larger number of crustaceans in the jar to then transplant them into the aquarium for further reproduction. Let's wait.

Well, today is the 4th day that the crustaceans in the jar have grown and given offspring and there are noticeably more of them. Let's transplant them into an aquarium for further breeding.

Daphnia in the aquarium

It should be noted that hunger is harmful for crustaceans and therefore you should always make sure that yeast is present in the water of daphnia. Let's feed the crustaceans.

A week has passed since the daphnia were transplanted into the aquarium. All these days the crustaceans were actively breeding and seemed to have completely forgotten about the cramped conditions. All this time I fed the daphnia once a day with yeast, and maintained the water temperature at 26 ° degrees. Daphnia has developed a lot and it’s time to give the fish a real feast!

The following important points should be noted: When catching daphnia, you should always leave a sufficient number of crustaceans for their further reproduction, since the rate of reproduction depends on the initial quantity.

Fresh water also has a beneficial effect on the reproduction of daphnia, so after about 2-3 weeks the water in the aquarium cultivator must be completely replaced, and it is more convenient to do this after the next catch of daphnia.

The need to change the water may be indicated by such factors as plaque on the glass, as well as the sluggish behavior of the crustaceans, which indicates that the conditions of detention have not changed for the better, and the daphnia dies, and under good conditions the crustaceans are always nimble and move quickly.

Buy Daphnia moina eggs

You can buy Daphnia moina eggs for breeding at home using the link:

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

When catching daphnia yourself, you need to take into account that they react strongly to lighting. When strong, they will tend to go deeper into the water, and when weak, upward or towards the light source.

Daphnia magna - larva about 0.7 mm, males 2 mm, females up to 6 mm. They ripen in 4-14 days. They produce up to 20 litters every 12-14 days. There are up to 80 eggs in a clutch. Life expectancy is 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. They produce up to 15 litters every 1 - 3 days. There are up to 22 eggs in a clutch.

Life expectancy is 30 days. Moina rectirostris - larva about 0.5 mm, males up to 1 mm, females up to 1.7 mm. Ripen in 3 - 4 days. They produce up to 7 litters every 1 - 2 days. There are up to 53 eggs in a clutch. Life expectancy is 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, angistrodesmus, etc.), bacteria.

Kinds

In the middle zone, the following types of daphnia crustaceans are most often found:
the largest Daphnia magna - female size up to 6 mm, male up to 2 mm, larva 0.7 mm, grows within 4-14 days, breeding interval 12-14 days, up to 80 eggs in one clutch, lives 110-150 days;
medium-sized crustaceans, 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: species of the moina genera, female up to 1.5 mm, male daphnia up to 1.1 mm, daphnia larva 0.5 mm, matures within 24 hours, 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 crustaceans is usually full plant foods, therefore they are useful for feeding aquarium fish deprived of a natural diet.

The shell of daphnia, consisting mainly of chitin, is not digested, but nevertheless serves as a valuable ballast substance that activates the intestinal function of fish that are deprived of the opportunity to actively move in the aquarium. The smallest Daphnia moina, popularly known as Daphnia “livebearer,” is well suited for feeding grown-up juvenile aquarium fish.

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

Find Daphnia for home care It’s not difficult: you can buy it or collect it in a pond. Ponds with waterfowl, lakes where there are few or no fish (both daphnia and diseases will be caught with fish), and containers with settled water are good for catching. The spoils at home are poured into a flat vessel, preferably white. This makes it more convenient to filter the future feed again, because... foreign organisms will settle to the bottom or attach to the white walls, where they are clearly visible.

If the collected crustaceans are used as food for fish, the water in which the live food lives is not poured into a common reservoir. Daphnia are selected with a net so as not to infect aquarium inhabitants. Daphnia Representatives of Cladocerans are kept in a shaded place, because They do not tolerate light well. Normal water temperature for life is in 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 until brownish, in 1 liter warm water dilute 3 grams. yeast; this is the standard proportion. Meat water is given from 0.5 to 2 cm3 per liter of water. Instead of pure chlorella, you can simply add green aquarium water. To ensure that the fish have high-quality food, horse manure and ammonium nitrate are added to the food.

How to breed daphnia at home?

A 15 liter bottle is perfect for growing daphnia. plastic container, or any other. In this case, several recommendations can be noted: 1. It is necessary to avoid container materials that are soluble in water and emit harmful chemical substances(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 regular aquarium, a large surface area with air is required for gas exchange, because daphnia are very demanding of oxygen content;

4. If the container is located outdoors in strong sunlight or other lighting conditions, it is recommended to use larger than 40 liter volumes to ensure a more stable aquatic environment. Additionally, when black aquarium material is used, it will heat up more than clear or yellow material, 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.

A good idea for growing daphnia in an aquarium is to connect the lighting via a timer, which can be purchased at an electrical supply store. It was found that Daphnia magna prefers weak aeration. In theory, aeration not only supports gas exchange, but also stabilizes water conditions and prevents the oppression of cultural development.

Daphnia pulex also likes light 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 ultimately lead to death (Artemia nauplii are also susceptible to this problem).

Catching

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

If the aquarist intends to catch daphnia from natural bodies of water, it is advisable to use a fine-mesh net or sieve (homemade from muslin fabric). Pass the net through the water evenly in a figure-eight motion, or scoop it up slowly. Do not allow the net cells to be too small and the water pressure to be too strong when catching, as this can lead to the death of the crustaceans.

Structure

A little more about the structure of daphnia. Aquarists use this name for various cladocerans. You can get an idea of ​​their appearance in the photo. In all representatives of daphnia, the body is strongly compressed laterally 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 ocellus next to it.

Also on the head there are two pairs of so-called antennas, the rear of which have big sizes and are additionally equipped with bristles that increase their area. It is due to the flapping of these antennas that daphnia move in the water. When stroked by the antennae, the body of the crustacean receives a spasmodic forward motion, for which daphnia received the second, popular name “water flea”.

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

A few days later the process is repeated. During this time, young female daphnia also grow up and become involved in the reproduction process. With a successful combination of circumstances, reproduction proceeds like an avalanche. This is why in summer, small bodies of water are often swarmed with daphnia, and the water appears reddish in color.

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

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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 Gammarus, Artemia and others. Due to its peculiar sudden movements it is often called a “water flea”. Not to mention the peculiarities of movement, daphnia is also similar in appearance to 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 arthropods. All Daphnia species have different variations, and sometimes members of the same species are very different from each other. The characteristics of the phenotype, body size and shape depend on the area of ​​​​origin and specific environmental conditions. Representatives of the genus Moina have significant similarities with daphnia.

It is important to distinguish the Daphnia crustacean from other "water fleas" such as copepods, Cyclops species and barnacle crustaceans, which often live in the same places. Abrupt movements, body shape and, to a lesser extent, coloration are the best criteria for discrimination without the need for microscopic examination.

The genus Daphnia has a very wide distribution, including Antarctica, where Daphnia studeri, previously assigned to the genus Daphniopsis, was discovered in the relict salt lakes of the Vestfold oasis. At the beginning of the 20th century, the prevailing opinion was that most species had a cosmopolitan distribution, but it later became clear 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 typical for equatorial regions, where daphnia are rare. The most diverse fauna is in the subtropics and temperate latitudes. In recent decades, the ranges of many species have changed due to human dispersal. Thus, a species from the New World, D. ambigua, was introduced into Europe. In many reservoirs in the southern United States, D. lumholtzi, which was previously found only in the Old World, has become common.

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In ponds and puddles in central Russia, the following crustaceans of the genus Daphnia are often found, and therefore the most popular among them. Daphnia magna (D. magna), female - up to 6 mm, male - up to 2 mm, newborns - 0.7 mm. They ripen within 10-14 days. Litters in 12-14 days. There are up to 80 eggs in a clutch, but usually 20-30. The lifespan of this crustacean is up to 3 months. Daphnia pulex (D. pulex), female - up to 3-4 mm, male - 1-2 mm. Litters in 3-5 days. There are up to 25 eggs in a clutch, 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 standing continental bodies of water and are also found in many slow-flowing rivers. In puddles, ponds and lakes they often have high numbers and biomass. Daphnia are typical planktonic crustaceans, spending most of their time in the water column. Various species inhabit small temporary reservoirs, littoral and pelagic zones of lakes. Quite a few species, especially those inhabiting arid areas, are halophiles, living in brackish, saline and hypersaline continental water bodies. These species include, for example, D. magna, D. atkinsoni, D.mediterranea, as well as most species previously classified in the genus Daphniopsis.

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. Many daphnia are also capable of slowly crawling along the bottom or walls of vessels due to water currents created by the thoracic legs; the antennae are motionless during this method of movement.

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

Ovid in his poem “Metamorphoses” told how once the golden-haired god of light Apollo carelessly laughed at Aphrodite’s son Eros (or, as the Greeks also called him, Eros). The offended god of love struck the silver-faced patron of the muses in the very heart with a golden bow. Having once met the beautiful Daphne, the 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, began 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 the appearance that brought her only grief. Old Penei 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 scent of which always reminded him of the elusive Daphne.

Reproduction in nature

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During the summer months, daphnia are often found in blooming ponds and lakes that have high concentrations 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 genotype of the parent, and any differences in the physiological state are determined by environmental conditions. Parthenogenesis allows daphnia to reproduce rapidly under favorable conditions, shortly after they emerge from the eggs. In nature, in late spring, summer and early autumn, depending on temperature, food availability and the presence of products of their metabolism, Daphnia reproduces parthenogenetically, giving birth to an average of 10 nauplii for each 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, with births occurring every three days. For your life cycle A female can give birth 25 times, but in practice this number is slightly less and a female tends to produce no more than 100 offspring.

When there is 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 go dormant and become covered with a dark brown/black saddle-shaped shell known as the ephippium. In this form, daphnia can carry harsh conditions environment, short-term drying out of the reservoir and even its freezing. Females born to form an ephippium are easily distinguished from parthenogenetic individuals because the developing ephippium is present in them as a black spot at the posterior end of the body. When environmental conditions become favorable again, a generation emerges from the eggs, which, in turn, gives birth to only females, while all males die before the onset of unfavorable conditions.

Fishing in natural reservoirs

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They catch daphnia with a net. A special net is needed for this - with a long handle up to 2-3 meters, usually made of several screwed sections, with a diameter of about 25-30 cm and a fabric cone about 50-60 cm long with a rounded end. The net ring is made of durable material, for example stainless wire with a diameter of 3-5mm. If you make it from a thinner one, it will bend easily, and considering the possible snags on the bottom... But the most difficult thing is to choose the fabric for the net. Here, synthetic materials are preferable, such as nylon, which do not rot from prolonged contact with water. The mesh size of the net depends on what you are going to catch; very fine 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.

They operate the net calmly, smoothly, without much effort, moving it with a figure of eight in places where daphnia accumulate. We did it a couple of times, took it out, shook out the catch, and began to fish further. If you push a full net, many daphnia will crumple and die, so it is better to take it out more often with small portions of prey. Otherwise, greed, you know, does not lead to good. For fishing, it is better to prefer smaller bodies of water, for example, puddles - there daphnia are more accustomed to oxygen starvation and will more easily endure further transportation. True, it is difficult to catch in small puddles with a standard net; there you have to use a net with a shorter cone - otherwise it begins to cling to the bottom and create turbidity. In order not to catch hydra with daphnia, you should try to catch prey away from thickets of aquatic plants or objects in the water to which it can attach. And in no case is it recommended to catch food in reservoirs where fish live - with such food you can easily introduce pathogens of various diseases.

The caught daphnia are placed in a container - a can or a special can for transportation. Before pouring, it is advisable to strain the catch through a thin mesh to remove any trapped debris and any large unwanted guests - swimming beetles or large dragonfly larvae. It is very desirable to have a battery-powered compressor in the transport container - it will keep most of the catch alive during the journey home.

At home, caught daphnia are poured into a wide flat vessel, for example a white enamel basin. There, for some time, all the unwanted organisms settle on the bottom and walls; on a white background, it is easy to spot the larvae of dragonflies and leeches, and everything else that has nothing to do with daphnia. There, at the bottom, dead crustaceans accumulate. 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 fish.

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

Daphnia can also pose a danger to 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-found opinion that an aquarium is harmful to health. In fact, the reason is pollen, with which crustaceans are literally “stuffed” during the period of mass flowering of grasses.

Breeding at home

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A 15 liter plastic container or any other is perfect for growing daphnia. In this case, several recommendations can be noted. Avoid container materials that are water soluble or release 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 regular aquarium, a large area of ​​​​contact with air is required for gas exchange, because daphnia are very demanding of oxygen content. If the container is located outdoors, in strong sunlight or other lighting, it is recommended to use larger than 40 liter volumes to ensure a stable water environment. In addition, when black pond material is used, it will heat up more than clear or yellow material, 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 aquarium cultivation, a good idea is to connect the lights via a timer, which can be purchased at an electrical store. It was found that Daphnia magna prefers weak aeration. In theory, aeration not only supports gas exchange, but also stabilizes water conditions and prevents inhibition of cultural development. Daphnia pulex also likes light aeration. It is necessary to avoid small air bubbles that can get under the carapace of daphnia, raise them to the surface, interfere with feeding and ultimately lead to death.

The best nutrient medium for the culture is blue-green algae. Typically, these are free-floating species of 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 process of maintaining the culture 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 algae development that require minimal effort.

Placing the culture container in direct sunlight will ensure algae development within two weeks, usually sooner. Their spores are airborne and colonize water bodies, but, as a rule, some algae is added to the water to speed up flowering. Using plant fertilizers such as Miracle grow. Once a week, add 1 teaspoon of fertilizer to a 4-liter container. The container must be under straight lines sun rays. Aeration and slow movement of water are necessary. A system should be built according to which the first container with algae is already green, the second will acquire this shade within two days, the third within another two 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 flowering water at his disposal, ready to be fed to 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 algae-rich because algae tend to raise the pH as high as 9. High alkalinity is associated with increased ammonia toxicity, even at low concentrations.

Baking, brewing and almost all other types of yeast are suitable for culturing Daphnia, but it is recommended to apply no more than 28 g per 20 liters of water as a daily rate. If you use yeast, you can additionally add algae to the water, which will prevent environmental pollution. It is important not to overdo it with adding 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, but ascorbic acid can lower the pH of the medium to 6, which is far from the ideal value for daphnia. This usually occurs when overfeeding.

The advantage of yeast as a nutrient medium is its ease of acquisition, and minimal effort in preparing and maintaining the culture. However, they are not as valuable from a nutritional point of view 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 optimal temperature is 18-22 0C. D. pulex thrives at temperatures above 10 0C. Moina can withstand even harsher fluctuations, 5-31 0C; the optimum is 24-31 0C. Moina's increased resistance to temperature makes it a preferred cultivation object when the optimum for D. magna under natural conditions is reached only once a year.

Daphnia are tolerant to dirty water, and dissolved oxygen levels can vary from almost zero to supersaturated. Like Artemia, Daphnia's ability to survive in oxygen-poor environments is due to its ability to form hemoglobin. Hemoglobin production may accelerate with increasing temperature and population density. Just as in the case of artemia, daphnia does not tolerate active aeration with small air bubbles, which can destroy it.

Producing daphnia is a relatively easy process. However, there are measures to increase cultivation productivity. Good aeration, good to the extent that the water is saturated with oxygen, but not excessively strong aeration, is the main factor in increasing productivity. Some species prefer the absence of aeration, but Daphnia magna grows better in its presence. In addition, this makes it possible to increase the density of the culture; water circulation reduces algae deposits on the walls of the vessel, and also transfers food particles into suspension, which is typical for the natural diet of daphnia. The only drawback is that small air bubbles fill the carapace of the crustaceans, which float up and cannot feed. Air spray should be avoided altogether, or it should be very rough to create large bubbles. Convenient in terms of aeration is the “bio-foam” filter. It is usually used in an aquarium with fry, but is ideal for daphnia. It captures large particles and helps them break down to feed algae.

Regular selection/collection of culture. This event maintains constant growth of the crop and provides daphnia with the opportunity to quickly accumulate oxygen and food. A 24-hour daylight period increases the productivity of daphnia, but this is not a necessary measure. Also, you should 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 of metabolites and toxins.

When it comes to cultivating daphnia, collecting them can be a real challenge, but it is an integral part of the entire breeding process. Otherwise, overpopulation becomes a serious problem. Even if you have to shake the crustaceans into 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 begin reproducing. When culling/catching, a net is used that has cells large enough to allow young crustaceans to pass through, but small enough to catch adults. Some aquarists recommend pouring ¼ of the container through the mesh and then filling the volume with a new portion of water with nutrient 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 into upper layer water.

Caught crustaceans can live for several days in a fish tank with fresh water. They show normal activity when the temperature rises. However the nutritional value Daphnia gradually declines because they are starving and must be provided with food for the best effect. Crayfish can be stored frozen for a long time if they are frozen in water with a low salt content (0.007 ‰, density - 1.0046). Of course, this will kill the daphnia, due to leaching 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 bound amino acids will be lost. Fish are not so willing to eat frozen crustaceans.