How many eyes does daphnia have. Big daphnia. What is the danger of Daphnia for humans

Daphnia or Daphnia are known to quite a few under the name "water fleas" from the genus of planktonic crustaceans. This family belongs to the superorder Cladocera. The water flea is very small insects with a body length of not more than six millimeters. Many inhabitants quite often attribute bites to these crustaceans, which look like fleas, but they are not.

Description of the species

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

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

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

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

To get rid of fleas, our readers advise the Pest-Reject repeller. The operation of the device is based on the technology of electro-magnetic pulses and ultrasonic waves! Absolutely safe, ecological product for humans and pets.

Habitat

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

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

Nutrition Features

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

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

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

Daphnia under the microscope (video)

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

Harm to humans

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

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

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

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

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

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

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

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

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

How water fleas breed (video)

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

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

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

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

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

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

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

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

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

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

Reproduction in nature

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

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

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

Fishing in natural waters

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

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

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

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

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

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

Breeding at home

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Tara

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

Physical conditions for keeping daphnia

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

What to feed

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

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

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

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

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

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

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

Aeration

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

How to increase productivity in the process of development?

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

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

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

The body of Daphnia is laterally compressed and everything, except for the head, is covered with a bivalve shell (carapace). Inside the shell, the body fits freely, being attached to it only by the front part.

Between the walls of the shell valves and the dorsal surface of the animal, females have a brood (embryonic) chamber. The edge of the shell on the dorsal side is elongated into a long spike (spina). The head is bent to the ventral side, the frontal part is extended into the rostrum directed downwards and backwards. The large median eye, formed by the fusion of two compound eyes that are embryonic, is equipped with special muscles that determine its mobility inside the eye chamber. Some species of daphnia also have a small unpaired eye. Short antennules, which are sensory organs, are articulated in females motionlessly with the head behind the rostrum; at the end they bear a bunch of sensitive bristles.

The antennae, which are the only organ of locomotion, are well developed, consisting of a large protopodite and two branches, the outer or exopodite and the inner or endopodite, armed with long feathered swimming setae. Strong musculature is visible inside the antennae. Each antenna is driven by three abductors, three adductors and one levator; the first two abductors and the levator are attached to the chitin of the dorsal part of the head with their conspicuous fan-shaped widened ends. The antenna rises due to the contraction of the adductors and the levator, the abductors are their antagonists.

The mandibles, which are clearly visible in living organisms by their peculiar movements, are devoid of a palp, on inside with a large chewing surface, consisting of chitinous plates armed with spines. Maxillules are reduced. Maxillae are completely absent. In total there are five pairs of pectoral legs, which are turgor limbs.

On the dorsal side of the abdomen (abdomen) there are several abdominal outgrowths that serve to close the brood chamber behind; behind these outgrowths there is a pair of feathered swimming or caudal setae. The posterior part of the abdomen behind the caudal setae is called the postabdomen or cauda. It is bent under the body of the organism so that its upper, or dorsal, edge, on which the anus opens and the anal teeth are located, becomes, as it were, the lower edge; at the end of the postabdomen is a furca formed by two strong and slightly curved claws called furcal or caudal claws.

The mouth, bounded from above by the upper lip, and from the sides by mandibles, leads to a short esophagus, passing into a long midgut, of the same diameter throughout its length; in the anterior part of the midgut there are paired hepatic outgrowths, which look like short and curved blind appendages located in the head.

The heart looks like a rounded bag with one pair of lateral awns. Heart contractions are made with great speed, at room temperature, up to 200-290 beats per minute, which is the limit for animals. Blood from the heart enters the lacunae of the body. The osmotic pressure of the blood at normal conditions equals two to four atmospheres. This circumstance has great importance to preserve the shape of the body and the elasticity of the limbs (turgor limbs).

The respiratory organs are the epipodites of the limbs, which are washed by currents of water caused by the rhythmic movements of the legs.

The excretory organs are paired armored (shell) glands located in the thickness of the shell valves, between the outer and inner layers, and are clearly visible after the valves are separated from the body of Daphnia.

The clearly visible brain consists of two merged halves. From its anterior part, nerves extend to the compound eye, and on the underside there is often an unpaired (naupliar) ocellus.

The female reproductive organs extend along the sides of the intestine from the first pair of legs to the postabdomen; short oviducts open on the dorsal side of the body in the back of the brood chamber.

All embryonic development of juveniles takes place in the brood chamber during the period between two molts. Daphnia form parthenogenetic and latent eggs. The latter are enclosed within the highly modified and dark-colored upper part of the shell valves, which forms the so-called ephippium (saddle).

Daphnia males differ from females in the absence of a brood chamber, the presence of large and mobile antennules, and other leg armament of the first pair.

A—B—Daphnia magna, female (A), male (C), female post-abdominal (C), D, E—Daphnia longispina, female (D), female post-abdomen (D); B - Dap cucullata, female; F, 3 - Daphnia cristata, female (F), antenna (3).

The five most common species of Daphnia differ from each other in the following ways.

Caudal claws armed with large spines at base

Upper (dorsal) postabdomen straight, without notch - D. pulex

Upper edge of postabdomen with notch - D. magna

Caudal claws lack large spines at base

Unpaired eye available - D. longispina

Unpaired ocellus absent

The rostrum is sharp, the setae of the antennules do not go beyond its end - D. cristata

The rostrum is obtuse, the setae of the antennules extend beyond its end - D. cucullaia

More interesting articles

• Daphnia ambigua Scourfield, 1947
• Daphnia atkinsoni Baird, 1859
• Daphnia arcuata Forbes, 1893
• Daphnia australis(Sergeev and Williams, 1985)
• Daphnia barbata Weltner, 1898
• Daphnia bolivari Richard, 1888
• Daphnia brooksi Dodson, 1985
• Daphnia carinata King, 1852
• Daphnia carvicervix Ekman, 1901
• Daphnia catawba Cocker, 1926
• Daphnia cheraphila Hebert and Finston, 1996
• Daphnia chevreuxi Richard, 1896
• Daphnia cristata G. O. Sars, 1862
• Daphnia cucullata G. O. Sars, 1862
• Daphnia curvirostris Eylmann, 1887
• Daphnia dadayana Daday, 1902 sensu Paggi, 1999
• Daphnia dubia Herrick, 1883
• Daphnia dolichocephala G.O. Sars, 1895
• Daphnia ephemeralis(Schwartz et Hebert, 1985)
• Daphnia exilis Herrick, 1895
• Daphnia galeata G. O. Sars, 1864
• Daphnia gessneri Herbst, 1968
• Daphnia hispanica Glagolev et Alonso, 1990
• Daphnia hyalina Leydig, 1860
• Daphnia jollyi Petkovski, 1973
• Daphnia lacustris G.O. Sars, 1862
• Daphnia laevis Birge, 1879
• Daphnia latispina Korinek and Hebert, 1996
• Daphnia longiremis G. O. Sars, 1862
• Daphnia longispina O. F. Mueller, 1785
• Daphnia lumholtzi G. O. Sars, 1885
• Daphnia magna Straus, 1820
• Daphnia magniceps Herrick, 1884
• Daphnia mediterranea Alonso, 1985
• Daphnia menucoensis Paggi, 1996
• Daphnia middendorffiana Fischer, 1851
• Daphnia minnehaha Herrick, 1884
• Daphnia nivalis Hebert, 1977
• Daphnia occidentalis Benzie 1986
• Daphnia obtusa Kurz, 1875
• Daphnia oregonensis Korinek and Hebert, 1996
• Daphnia pamirensis Rylov, 1928
• Daphnia parvula Fordyce, 1901
• Daphnia peruviana Harding, 1955
• Daphnia pileata Hebert and Finston, 1996
• Daphnia prolata Hebert and Finston, 1996
• Daphnia psittacea Baird, 1850
• Daphnia pulex Leydig, 1860
• Daphnia pulicaria Forbes, 1893
• Daphnia pusilla(Serventy, 1929)
• Daphnia retrocurva Forbes, 1882
• Daphnia quadrangula(Sergeev, 1990)
• Daphnia queenslandensis(Sergeev, 1990)
• Daphnia rosea(G. O. Sars, 1862)
• Daphnia salina Hebert and Finston, 1993
• Daphnia schoedleri G. O. Sars, 1862
• Daphnia similis Claus, 1876
• Daphnia similoides Hudec, 1991
• Daphnia sinevi Kotov, Ishida and Taylor, 2006
• Daphnia stuederi(Ruhe, 1914)
• Daphnia tanakai Ishida, Kotov and Taylor, 2006
• Daphnia tenebrosa(G. O. Sars, 1898)
• Daphnia tibetana(G.O. Sars, 1903)
• Daphnia thomsoni G.O. Sars, 1894
• Daphnia thorata Forbes, 1893
• Daphnia triquetra G.O. Sars, 1903
• Daphnia truncata(Hebert et Wilson, 2000)
• Daphnia turbinata G. O. Sars, 1903
• Daphnia umbra
• Daphnia villosa Korinek and Hebert, 1996
• Daphnia wardi(Hebert et Wilson, 2000)

Daphnia(genus Daphnia O. F. Mueller, 1785) - planktonic crustaceans from the superorder Cladocerans ( Cladocera), belong to the group Daphniformes, family Daphniidae.

Systematics

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

Most taxonomists recognize the division of this genus into two subgenera - Daphnia (Daphnia) O.F. Mueller, 1785 and Daphnia (Ctenodaphnia) Dybowski et Grochjwski, 1895. The representatives of the subgenus Daphnia (Daphnia) notch of head shield absent, egg chambers of ephippium usually almost perpendicular to dorsal margin of valves. The representatives of the subgenus Daphnia (Ctenodaphnia) notch of head shield present, egg chambers of ephippium usually nearly parallel to dorsal margin of valves.

External structure

Unless otherwise noted, this section describes the structure of females. The integuments consist of a head shield and a bivalve carapace. Usually they have a well-marked pattern of rhombuses and polygons - reticulation. Each such cell of the integument is formed by one cell of the hypodermis. There are spines on the edge of the valves, and a tail needle covered with spines at the posterior end. Many species have a row of feathered setae on the inner margin of the valves in its middle part; males of all species have the same setae and additional setae on the anterior-lower corner of the valves.
On the head, most species have a beak-shaped outgrowth - the rostrum. Under it are the first antennae (antennules) - short outgrowths bearing 9 olfactory setae - aesthetas at the end, and one additional seta on the lateral surface. In males, the first antennae are larger, mobile; in addition to the aesthetasci, they bear a large bristle ("flagellum") at the distal end.
On the lateral surface of the head there are protrusions of the cuticle - fornixes. Their shape, as well as the shape of the posterior edge of the head shield, is an important diagnostic feature of subgenera and groups of species. Under the fornixes, the second antennae (antennae) are attached to the head with a complex "joint". They consist of a base and two branches - an internal three-segmented and an external four-segmented. At the ends of the segments of the branches there are two-segmented swimming bristles covered with flattened hairs, which form "oars" when swimming. There are five of them on a three-segmented branch (four only in D.cristata), on a four-segmented branch - four. There are several small sensitive bristles on the base.
A large upper lip extends from the back of the head. Inside it are several giant polyploid cells that secrete a secret that glues food into a food bolus.
On the border between the head shield and the carapace, mandibles are located under the valves. They have a complex shape, are asymmetrical and have highly chitinous chewing surfaces covered with ridges and outgrowths. In the process of feeding, the mandibles transport food to the mouth opening.
Under the carapace are small first maxillae (maxillae), bearing four setae. Maxillae II are reduced in Daphnia. There are five pairs of biramous thoracic legs of complex structure. The legs of the first and partly of the second pair differ in structure in males and females. On the first pair of legs of males there are hook-shaped outgrowths that allow them to cling to females during mating. The third and fourth pairs have several filtering bristles. Each leg has a respiratory appendage - the epipodite.
Per thoracic region a reduced abdominal is located, the presence of which is "marked" by dorsal abdominal outgrowths that close the exit from the brood chamber. There are usually four of them, they are well developed in mature females and reduced in males of most species.
The posterior part of the body is a large mobile post-abdomen homologous to the telson of other crustaceans. On its dorsal side are two rows of teeth, between which is the anus. At the end of the postabdomen there are paired claws covered with spines. According to some data, they are homologous to the furca, according to others, they are a pair of large modified setae. The postabdomen serves to clean the filtration apparatus from large foreign particles.

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 supraesophageal ganglion (brain) and the ventral nerve cord with several paired ganglia. The brain is clearly visible in living individuals, which is extremely rare. It consists of a large, bisected optic ganglion and the supraesophageal ganglion proper. From the anterior part of the optic ganglion, the optic nerve departs, connecting the brain with a complex compound eye. The unpaired compound eye in Daphnia is formed from a paired primordium (embryos have two eyes) and contains exactly 22 facets (ommatidia). It is located in a special cavity inside the head and is driven by three pairs of oculomotor muscles. In living individuals, an eye tremor is noticeable, larger jumps (saccades) of the eye are observed from time to time. Nerves also depart from the brain to the eye ( 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.

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

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

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

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

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

Paired ovaries (in males - testes) are located on the sides of the intestine. The eggs, as they mature, move to their posterior end, where narrow oviducts are located that open into the brood chamber. In males, the seminal ducts open on the postabdomen in its distal part, in many species on special papillae.

Moult

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

Spreading

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

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

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

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

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

Biology

Daphnia are small crustaceans (body sizes of adults are from 0.6 to 6 mm). They inhabit all types of stagnant continental water bodies, and are also found in many slow-flowing rivers. In puddles, ponds and lakes, they often have a high abundance and biomass.

Breeding

1. Vessel made of glass or plexiglass. Water: 20 - 24°С, for washings 26 - 27°С, dH 6 - 18°, pH 7.2 - 8. weak aeration that does not lift dirt from the bottom, weak light for at least 14 - 16 hours a day. Food: baker's yeast, frozen to Brown color and divorced in warm water with a temperature not higher than 35 ° C, at the rate of 1 - 3 g per 1 liter of water in a vessel. Give 2-3 times a week. The optimal density of crustaceans is 100-150 pieces/l. Catch 1/3 of juveniles daily. 1 time within 5 days for daphnia, do the culture again. Clean the vessel from dirt and change the water.

2. Vessel made of glass or plexiglass, not less than 3 l. Aquarium water, 18-25°С. Strong lighting for algae development. Grind dried elodea, lettuce or nettle leaves into powder, strain through cheesecloth and dip into water. When the water turns green, add crustaceans. Re-arrange once every 10-15 days.

3. Vessel made of glass or plexiglass. Water from the reservoir where the crustaceans were taken from, or aquarium water, 20 - 24 ° С. Weak aeration. Lighting for at least 14 hours. Feed: stale blood (1.5 - 2 cc per 1 liter of water), blood meal, meat and bone meal (0.5 - 2.5 cc per 10 liters of water).

Links

http://wfleabase.org/database Synonym Dictionary

The ancient Russian name for the bay leaf, which came to Russia from Byzantium and was used until the beginning of the 18th century. (Culinary Dictionary of V.V. Pokhlebkin, 2002) * * * (