Life cycle of daphnia. The structure of daphnia (Daphnia)
- a genus of planktonic crustaceans from the superorder Cladocera. Sizes from 0.2 to 6 mm in length. Daphnia are sometimes called water fleas.
Daphnia is the most famous crustacean from the composition of "live dust", which is used as food for aquarium fish OK.
Due to the many live daphnia, the water in the tank resembles a yellow-orange mixture. IN winter time it is sold dried.
Several hundred species of cladocerans are known. The bodies of most of them are enclosed in a translucent bivalve shell, fastened on the back and diverging on the ventral side. Branched antennae-antennae extend from the head of the crustacean, hence the name of the crustaceans - branched. Whiskers-antennas are the rowing organs of the crustacean.
Oddly enough, daphnia even have a heart. Reducing several hundred times a minute, it pushes the blood first to the head, and then to the gills and the posterior end of the body.
By adjusting the frequency of the flapping of the antennae, daphnia can not only "soar", but also rise to the upper layers of the water or, conversely, go to the depths. Thus, they make vertical movements (migrations) associated with the search for food, changes in water temperature or time of day.
Only in Europe there are more than a dozen of their species, and therefore in one jar of "live food" there may well be several species at once. All of them are fundamentally very similar. Like any planktonic organisms, daphnia spend their whole lives as if in a suspended state. However, "hanging" in the water is not easy even for these tiny animals. Dead daphnia, although slowly, goes to the bottom.
With a lack of food, daphnia stop reproducing and die. This is why "live food" is easier to catch in a small, dirty pond or ditch than in a lake with clear water: in clean water very few bacteria. But daphnia also does not like an excess of bacteria: microorganisms release so many toxic substances into the water that the life of crustaceans becomes impossible.
In spring and summer, you will definitely find cladocerans in almost every body of water: they are in lake bays, and in small ponds, and in puddles. Sometimes there are so many of them that the water from them really takes on gray, greenish, red-brown color.
It has long been noticed that cladocerans react in their own way to the amount of oxygen dissolved in water - depending on this, they change their color. If there is little oxygen dissolved in the water (and this happens in reservoirs with so-called “bad” water during hot weather), then the crustaceans acquire a dark red color. And if there is a lot of oxygen in the water, then the crustaceans are colored much lighter - this changes the color of the crustaceans' blood.
Most branched crustaceans feed on various microorganisms found in the water: bacteria, ciliates, algae. Since these crustaceans can also absorb small species of algae, they are often settled in an aquarium where the water has bloomed, and the crustaceans purify the bloomed water.
Appearing in the waters in early spring, all the warm summer time, daphnia intensively breeds from unfertilized eggs (about 80 pieces), which it carries on its back in the embryonic sac. A new generation is displayed every 3-4 days. After 8-10 days, newborns themselves begin to give birth, literally filling small reservoirs with themselves, which often leads to self-destruction due to lack of food - ciliates.
By the end of summer, with a cold snap, males are born from some Daphnia eggs and fertilized eggs begin to appear, enclosed in a dense saddle shell. In the saddle (daphnia wears it on its back) there are no more than two eggs. Once free, saddles can float on the surface of the reservoir or, depending on the type of daphnia, sink to the bottom. Eggs resting in saddles endure freezing and drying. New life begins with the onset of heat and the presence of moisture, when only females reappear from the "winter" eggs.
Depending on the habitat, daphnia come in different colors: in spacious reservoirs with oxygen-rich water, a light gray or greenish crustacean is found, in small pits with almost spoiled water - red. Red daphnia is the most nutritious, it lasts longer than others at home.
During the day, when the sun is shining, daphnia goes deep into the reservoir, into cloudy days and gathers off the coast in the evenings. All this provided that she lives in enough fresh water. In musty water, the crustacean constantly stays near the shores. In the evening, it is more from the side opposite the sunset, but in general it is where the wind blows from.
Catching daphnia is no different from catching cyclops and diptomus, but since it is sensitive to a lack of oxygen in the water, it should be carried Special attention. The container should be larger, and the crustacean in it should be smaller. Ambient air temperature and crossing distance must also be taken into account. Increases the chances of success at least partial (at stops) aeration of the water in the cann using a pear from a spray gun and a simple sprayer and replacing part of the water with fresh water.
Keeping daphnia alive is difficult. Not a large number of, placed in a low wide basin, can be saved only for one or two days in a cool place with frequent removal of dead crustaceans. Accumulating at the bottom, they quickly decompose and spoil the water, which is why their living counterparts die. It is necessary to remove the dead crustacean completely.
Daphnia breed quite unusually. Females have a cavity called a "brood chamber" located on their back and protected by the upper edge of the shell. IN summer period 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.
By the end of summer, with a cold snap, males are born from some Daphnia eggs and fertilized eggs begin to appear, enclosed in a dense saddle shell. In the saddle (daphnia wears it on its back) there are no more than two eggs. Once free, saddles can float on the surface of the reservoir or, depending on the type of daphnia, sink to the bottom. They are called ephippies. They are able to withstand drying and winter frosts, and can be carried with dust. A new life begins with the onset of heat and the presence of moisture, when only females reappear from the "winter" eggs.
In the middle lane, the following types of 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: species of the genera Moina, 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
When catching daphnia on your own it must be borne in mind 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.
It should be taken into account that in the water bodies inhabited by moins, puleks and magna, 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 of very fine fabric, and then pass 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 change in 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 sun rays. To increase the density of planting crustaceans, you have to do aeration, as in an aquarium.
If necessary, a small number of daphnia can be propagated at home, but this is a rather complicated process. Below are a couple of ways:
1) 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.
2) Use a glass or Plexiglas vessel with water temperature 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 divorced 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, change the water and breed the culture again. It is possible to use several vessels, starting them with a delay of several days, which provides a continuous pipeline for the production of daphnia.
There are other options for feeding. 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.
Synonyms: Water flea
Freshwater organisms, which have long been widely used as high-quality universal food for. In nature, these individuals inhabit ponds and lakes, but it is also quite possible to grow them indoors.
Description and types for home breeding
Daphnia are predominantly small crustaceans that are traditionally classified as "living dust". Let us dwell in more detail on the structure of daphnia. In all individuals of this group, the body is tightly compressed on the sides and has a chitinous bivalve cover - a shell attached to the back. 
Two eyes are located on the head, often merging in sexually mature organisms into one compound eye, and in some specimens, another auxiliary eye can be observed next to the compound eye. In addition, there are two pairs of peculiar antennae on the head of the crustacean. The posterior pair is larger and is equipped with auxiliary bristles. It is thanks to the volume of the rear antennae that individuals move in the water.
Often in reservoirs you can find the following types of microscopic crustaceans:
- magna - the largest representative of the culture (the body of the female grows up to 6 mm);
- puleks - individuals of medium size (the female reaches 3-4 mm);
- moina is the smallest type of crustacean (the maximum size of a female is 1.5 mm).
Did you know? It is curious that with a change in the level of pollution of the reservoir in which daphnia live, like a litmus test, the color of the body of these small organisms also changes.
How Do Daphnia Reproduce?
The breeding process of Daphnia is quite interesting. On the body of the female (on the back) one can observe the so-called "brood chamber". This cavity is securely guarded by the upper end of the shell. In summer, under the right climatic conditions, the female lays unfertilized eggs in this space, the number of which varies from 50 to 100 pieces. Only females hatch from these eggs. The young then leave the mother's cavity. A few days later, this phenomenon repeats itself. During these days, the young have time to grow up and connect to the breeding procedure. Ideally, this process proceeds in an avalanche-like manner.
At the end of the summer season and in early September, due to the deterioration of the climate, males hatch from a row of eggs. The males then inseminate the females. In females, new eggs are formed, wrapped in a dense coating (ephippium). The shell of the eggs is able to tolerate enough low temperatures. With the advent of spring, thanks to the warmth and moisture, ephippia awaken to life. Females emerge from them, and the cycle repeats. For your life cycle a female daphnia may have time to "give birth" 25 times, but in practice this number is usually less. 
Did you know? Among all multicellular organisms whose genome has been deciphered and studied, the owners largest number genes are daphnia. If the human genome contains approximately 20-25 thousand genes, then the genome of a microscopic crustacean has more than 30 thousand. Moreover, more than 10 thousand of these genes have no analogues among other living organisms. Thanks to this fact daphnia, along with mouse, yeast and fruit fly, is used for laboratory testing as a "model" organism.
How to independently catch in reservoirs
It is customary to catch Daphnia from the spring season until the end of autumn, until an ice crust forms on the reservoirs.
It is better to catch small crustaceans with an ordinary canvas net. Then they are passed through sieves, sorting individuals by size.
It is necessary to go fishing in the most calm and cloudy weather. Usually it should be in the morning or evening. In such conditions, crustaceans rise closer to the surface of the water. 
In the process of catching daphnia, they are periodically shaken out into a special tin vessel. In the same cans, the crustaceans are then transported. Do not forget that at very high density, individuals may die during transportation.
How to breed at home
When starting to grow freshwater organisms, you should first prepare a suitable container. In addition, you must know how to create all the necessary conditions for these individuals. It is about how to properly breed daphnia at home that will be discussed later in the article.
Vessel or aquarium for growing
For growing "live food" a container with a volume of 15-20 liters is excellent. When choosing a vessel, consider the following guidelines:
- choose a material that does not release hazardous substances into the water chemical substances(for example, synthetic polymers). The ideal container is a glass vessel or aquarium;
- if you use a simple glass vessel, the area in contact with air should be extremely large. This condition is required for natural gas exchange and supply of small crustaceans with oxygen;
- if you nevertheless chose a metal container - it should not be made of stainless steel;
- if you plan to keep the shellfish container indoors with bright lights or outdoors under bright rays sun - take a container with a minimum volume of 40 liters.
Physical conditions
- Temperature . Crustaceans adapt to a wide range of temperatures. The ideal temperature is +18-22 °C. Daphnia pulex perfectly withstands fluctuations above 10 ° C. For the magna crustacean in nature, the optimum temperature is reached only once a year.
- Salinity . Daphnia is a freshwater living organism. The genus of planktonic crustaceans to which it belongs does not include marine representatives. 99% of crustaceans are freshwater, while the rest live mainly in brackish and sea water. Individual specimens have been found in water with a salinity of over 0.004 ppm.
- pH and ammonia . The optimal pH is 6.5-9.5. Ammonia, even in low concentrations, is toxic to all living organisms. However, in an alkaline environment, the level of ammonia toxicity rises sharply, which does not affect the health of daphnia, but negatively affects the reproduction of individuals. So, the insignificant content of pH and ammonia does not pose a threat to the successful breeding of Daphnia. A significant increase in the hydrogen index increases the toxicity of dissolved gases and minerals.
- Oxygen . The crayfish feel good in dirty water. In this case, the dissolved oxygen index can vary from almost zero to supersaturated level. Such endurance of the culture is due to the ability to form hemoglobin. The crustaceans do not withstand intensive air exchange with small air bubbles. These bubbles can kill small individuals. However, very slow aeration can also kill small crustaceans. Slow air exchange forms a foaming layer harmful to these living organisms on the surface of the water.
- Dissolved Minerals . Crustaceans are very vulnerable to changes in the chemical component of their environment. They die when magnesium, potassium, zinc, sodium and calcium are added. A low phosphorus content activates the reproduction process, however, saturation exceeding 0.001 ppm is fatal to young animals. Even the lowest copper content causes a decline in the mobility of these organisms. To the content of dissolved toxins (pesticides, bleaches, detergents), small organisms are also very susceptible. In turn, nitrogen, which stimulates the growth of algae, does not affect daphnia. To get rid of chlorine in the aquarium, aeration or dechlorination should be applied. You can also add a small dose of tuff stone (in powder form). City or natural waters are usually too polluted. You can not use distilled water, as it does not contain the required minerals. For daphnia, it is better to take water that is drawn from an aquarium with fish. Filtered lake water or rainwater can also be used.
A home for aquarium fish and other aquatic life needs high-quality clean water, because otherwise your swimming pets will not be very happy and, most likely, will not live with you. Read how to choose and how to use an aquarium conditioner.
As for what Daphnia eats, then in natural conditions The diet of this culture consists of bacteria, yeast and microalgae.
Bacteria of small crustaceans are extracted from banana peel and other food waste. In addition, bacteria can be obtained from ordinary excrement. If you decide to use excrement, soak it in water beforehand and insist for several days. The water will begin to turn cloudy, indicating bacterial growth. After 6-7 days, pour healthy water into a vessel with fish in a ratio of 450 ml per 20 liters. Repeat the procedure every 5-6 days. 
Yeast is suitable for ordinary bakers. The daily norm for crustaceans is 28 g per 20 liters of water.
At the same time, add microalgae, which prevents clogging of water and serves as another source of nutrition for the culture. Algae supply in large enough quantities. To do this, scoop up water from a populated aquarium, place it under the rays of the sun, so that the "sea hay" is intensively formed.
To diversify the diet of daphnia, as well as provide them with vitamins, periodically add cabbage, beet or carrot juice to the aquarium (1 teaspoon per 5 liters of water). An excellent effect is also given by liquid manure, added in small quantities.
Important! As food for small crustaceans, it is not recommended to pour milk or hay decoction into the aquarium - these components inhibit the development and reproduction of individuals.
As you can see, growing small crustaceans indoors is quite easy. These small organisms make excellent food for your home aquarium inhabitants.
Genus: Daphnia = Daphnia
Daphnia is the common "popular name" for all types of cladocerans (CLADOCERA). Under this name, there are about 420 different species of cladocerans belonging to approximately 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 from the sides and enclosed in a bivalve chitinous shell, fastened on the back and diverging on the ventral side. Daphnia periodically sheds this shell and replaces it with a new one. Daphnia's head is elongated in front into a pointed "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 antennae on the head. The anterior antennae are rod-shaped, very small. But the rear antennae are disproportionately large compared to the body. They are branched, with each branch of the antenna provided with long feathery setae. The posterior antennae serve as the main organ of locomotion in cladocerans, simultaneously waving both posterior antennae, the crustaceans are repelled by them and thus swim in short leaps. By adjusting the frequency of the flapping of the antennas, daphnia can not only "soar", but also rise to the upper layers of the water or, conversely, go to the depths. Thus, they make vertical movements (migrations) associated with the search for food, changes in water temperature or time of day. Thoracic 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 an extensive cavity that performs the task of a brood chamber. Eggs are laid in this bag, where they develop.
In summer, in warm weather, in the brood chamber of the female, unfertilized eggs are formed (50-100 pieces for each individual), from which only females emerge, leaving the mother's body very quickly. 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 eggs begin to form in females, which can develop only after fertilization by the male. Daphnia males are rare, usually appear by autumn and are always much smaller than females. After fertilization of females by them, eggs are formed (usually no more than two), rich in yolk and completely opaque. The shell with eggs forms a saddle, or ephippium. Ephippia are free-floating or sinking to the bottom, they tolerate freezing and desiccation. Dried ephippia are carried by the wind. Heat and moisture awaken the eggs to life; females are bred from them, capable of reproducing in the virgin way for many generations. The color 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. Branched crustaceans feed on unicellular algae, bacteria and ciliates, which they suck into their mouths with a stream of water created by the movement of their legs. Usually, in nature, there is a sharp increase in the number of daphnia after the death of phytoplankton.
Cladocerans are present in almost every reservoir. But the largest number daphnia is found in stagnant waters (ponds, lakes, ditches, water pits) 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 from their number becomes red-brown.
Most major representative genus Daphnia magna (Daphnia magna Straus). Lives in shallow water bodies (ponds, pits, forest puddles). Females reach 5 - 6 mm in length, males - 2 mm, larvae - about 0.7 mm. Ripens at the age of 4 - 14 days. Give up to 20 litters every 12 - 14 days. Clutch up to 80 eggs. Life expectancy - 110 - 150 days. Daphnia pulex (Daphnia pulex De Geer) is widespread in shallow water bodies. Crustaceans of medium size, their size is up to 4 mm; Give up to 12 litters every 3 - 5 days. Each clutch contains up to 25 eggs. Life expectancy 26 - 47 days.
Daphnia longispina (Daphnia longispina Muller) their size is up to 4mm. Lives in both shallow and deep waters. It has a number of different forms.
Simocephalus (Simoctphalus) - flat crustaceans, often painted red. Habitat shallow ponds with stagnant water. Their body length ranges from 2 to 4 mm.
Ceriodaphnia (Ceriodaphnia), the shape and size is similar to the 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. Give up to 7 litters every 1 - 2 days. Clutch up to 53 eggs. Life span 22 days. Moina as a food item has a number of advantages over other Daphnia species. 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 Daphnia species reaches 4 mm. The chitinous shell of the moina is much softer. Juveniles of various species of aquarium fish grow much faster when fed with moina and reach puberty earlier than when fed with other types of food. Biochemical analysis showed that the nutritional value of Moina macrocopa is 20% higher than that of Daphnia magna. Moina's body contains more than 50% protein. Its reproduction rate is approximately three times higher than that of Daphnia pulex.
Bosmina (Bosmina) is one of the smallest representatives of cladocerans with long beak-like appendages on the head. Bosmins are often caught when catching 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 of aquatic plants.
Chidorus (Chydorus) are small crustaceans, characterized by their rounded shape and small size. Cladocera - one of the best aquarium feed for medium-sized fish species, as well as juveniles of almost all species. Fish eat them willingly, with appetite, and grow much better on them than on many other types of food.
Some species of daphnia are specially cultivated in fish farms as a highly valuable food for juvenile fish. Daphnia are one of the most complete aquarium foods. The high protein content, a large number of trace elements and vitamins, the optimal amino acid composition of the protein - all this makes daphnia a very popular food for aquarium fish among aquarists around the world.
Daphnia is the most famous and numerous representative of the Daphniidae family. The skin of this organism is bivalve, with two hooks at the end of the body and one spherical, movable eye, which is set in motion by three pairs. The body of Daphnia is transparent and allows you to see everything that happens in its body. Even the slightest contraction of the muscles of a crustacean can, if desired, be examined under a microscope.
Features of the internal structure
Despite its miniature size, a rather amazing organism is water flea. Description of the species notes a lot interesting features in her internal structure. Daphnia's kidneys are located near the mouth, the brain is near the esophagus, and the heart is on the back of the body. The blood is yellowish in color, contains white bodies - phagocytes, which, if necessary, protect the body of the crustacean from bacteria, fungi and foreign microorganisms.
The water flea has five pairs of legs, but they serve not so much for movement as for directing the flow of water to the mouth, which it filters for the presence of nutrients. Breathing is carried out directly through the integument of the body.
Distribution and living conditions
Daphnia have a wide distribution in almost all the globe. Most of them are in the subtropics and in latitudes with temperate climate. Basically, the water flea lives in stagnant water bodies (lakes, ponds, slow-flowing rivers), as well as in puddles. It multiplies rapidly, is extremely tenacious, so its numbers are quite large. Usually located in the water column, moves in leaps or crawls along the bottom (due to the pectoral legs).
In summer, daphnia swim quickly, but when unfavorable times come, they freeze. Even if the puddle they were in dries up, they come back to life as soon as it fills up again.
Most daphnia are herbivores, but there are also predators. The water flea recycles phytoplankton, fungi, bacteria, and rotting remains of animal tissue after being used by large predators.
The most common types
The Daphnia family is quite numerous. Only in Europe and North America there are about 150 species of these crustaceans. In Russia, some of them are especially common - magna, pulex, cuculata, galeata, cristata. All of them live in a variety of water bodies.
The largest water flea is Daphnia magna. Its female has a length of up to 6 mm, while the male is three times smaller. The maturation period of newborn daphnia lasts two weeks. The female also lays eggs every two weeks (about three dozen eggs). At first, newborns are microscopic in size. But then they grow rapidly. This species lives for about three months.
Another common species is Daphnia pulex. Representatives of its slightly smaller size - females are about four millimeters, males are two times smaller. They are very prolific - a clutch of fifteen eggs occurs once every five. These water fleas live for a relatively long time - the life cycle can be up to one and a half months. It varies depending on the conditions of existence. For example, an increase in temperature shortens life due to the fact that the metabolism of crustaceans increases.
reproduction
Water fleas are unusually prolific. In all Daphnia, egg laying is divided into winter and summer. Eggs in a certain period have their own characteristics. So, for example, in winter laying, they are covered with a denser shell and their number is small (about 2 pieces), and in summer they are much more. All these features are no longer due to the change of seasons and conditions of existence, but to the presence of males. In summer, when the male population is very low, Daphnia eggs appear and lay without fertilization. Eggs fertilized by males are laid only once a year - in autumn. During her life cycle, the female is able to give offspring up to 25 times.
Daphnia harm to humans
Despite the fact that daphnia is called a water flea, it has nothing to do with bites. However, it can cause harm to a person. Everything is in a high degree of allergenicity. This is due to the fact that during the period of violent flowering of plants, pollen enters the water in which daphnia are located, and they, in turn, filtering it, can capture those same pollen particles. Then, when the crustaceans are dried, this pollen remains and can cause a severe allergic reaction in the human body, which is often mistaken for a water flea bite.
Allergy symptoms are often typical - inflammation of the conjunctiva of the eye (conjunctivitis), watery eyes, frequent sneezing, nasal congestion, and difficulty breathing.
Sometimes there may also be rashes on the body, accompanied by severe itching.
Human use of daphnia
In turn, daphnia serve as a universal food for aquarium fish. For this purpose, they are bred at home.
You just need to catch daphnia in a stagnant pond and provide them with living conditions close to natural. It is worth catching crustaceans in water bodies where there are few or no fish, since in the absence of predators, daphnia will be more and less likely to be affected by any infection.
Breeding conditions
Water fleas in an aquarium should be kept in the water in which they live, because there is no food that they feed on in tap water. You also need to be careful about the choice of containers in which the crustaceans will be contained. After all, materials such as, for example, polypropylene, upon contact with water, can release harmful substances, and daphnia will simply die.
Daphnia kept in aquarium conditions need a lot of light. In a well-lit room, they feel great and give good offspring. In addition, daphnia cannot tolerate crowding. Since they multiply quickly, you need to constantly make sure that they have enough space and periodically move some of the water fleas to another aquarium. This can be explained by the fact that crustaceans are very sensitive to a lack of oxygen and quickly die without getting it.
Many daphnia aquarists note that the best food for them is baker's yeast. Only you need to feed the daphnia carefully - if you pour too much food, the water will become cloudy, and the crustaceans will not have enough oxygen. For an aquarium of five liters, you need an amount of yeast equal to the size of a match head. It is necessary to stir them in a teaspoon of water and gradually pour into the aquarium. Also, green algae, including Chlorella, serve as food for crustaceans.
It is important to note that they also need a certain temperature. This, according to experts, is from 22 to 25 degrees. It is under such conditions that water fleas breed in the pool of a natural reservoir.
It is necessary to prevent water seething and change the water (a third of the total volume) at least once or twice a week.
Daphnia crustaceans perfectly filter water from bacteria. Therefore, many aquarists breed them to purify water - it does not bloom and remains clean for a long time.
At first glance, it may seem that breeding daphnia at home is a very painstaking, time-consuming process. Nevertheless, these crustaceans are year-round ecological clean food for most fish species (both fry and adults).
The water flea is very sensitive to environmental pollution and changes in its ionic composition (sodium, magnesium, calcium, and so on). It is for this reason that crustaceans are often used to determine the quality of water (both tap water and water from open reservoirs).
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 daphnia's light, transparent body 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 important practical value 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.
