Daphnia. Daphnia crustacean. Daphnia lifestyle and habitat The Daphnia population of freshwater crustaceans consists

Daphnia  - This is an ordinary small crustacean with a magnitude of 3-5 mm.

External structure

The body of Daphnia is flattened laterally and enclosed in a transparent chitinous shell - shell. The head is not covered by a sink; in front of it is a large, complex eye. On both sides of the head there are large branchy tendrils directed forward and upward. The antennae continuously wave up and down and, accordingly, the crustacean itself also jumps in the water (therefore, daphnia has a second name - flea). Daphnia are flattened like a leaf sheet.

Lifestyle

Eating, daphnia jumps all the time, staying almost in one place.

Through the transparent shutters of the shell you can see the continuously working chest legs, they drive water under the shell. Water washes the gills located at the base of the foot, and the microorganisms present in the water go to feed Daphnia.

Reproduction and development

In summer, usually all daphnia living in a pond are females. On the dorsal side, under the shell, you can see the brood chamber with eggs. Young hatching occurs here, then they go outside, and new eggs appear in the chamber. Development is very fast, every 2-4 days a new generation is formed - several dozen young Daphnii. They are all also females and after 6-12 days (depending on temperature) also begin to breed. Therefore, it is not surprising that the number of Daphnia increases so quickly that in the middle of summer water literally teems with them.

This method of reproduction from unfertilized eggs is called parthenogenesis  (virgin reproduction).

Daphnia males emerge from fertilized eggs only when the water gets colder. In the fall, with the advent of males, females lay fertilized eggs. There are few eggs (usually 2), but they are large and very resistant to various adverse conditions - freezing, drying. In the spring of them, only females reappear, and the cycle of alternating parthenogenetic and dioecious generations is repeated again.   Material from the site

Position in taxonomy (classification)

Daphnia is classified as Arthropods, subtype Crustaceans, Gillopods, subclass Leaffoot.

Daphnia belong to the genus of crustacean planktonic. On the head there are branched tendrils, which is why the taxonomy classifies them as an order of the branched. They live everywhere, including Antarctica. You can meet their populations in any body of water, whether it be a puddle, a pond, a lake, a river. The water flea spends the cold season in the bottom layer. With the onset of heat, it activates and, under favorable conditions, begins to multiply rapidly.

There are more than 150 species of daphnia, which may have a different color, body length. In the CIS, such species as galeate, cristate, pullex, magna are common. The sizes of daphnia vary in the range of 0.5-6 mm. The body is covered with a transparent shell fastened on the back. The antennae, covered with bristles, help the water flea move and make vertical movements in the water column.

In addition to antennas, there is one moving eye on the head, consisting of several small eyes, a cranberry outgrowth - rostrum. Due to the transparency of the body, you can use a microscope or a photo to examine in detail the internal structure. The heart of Daphnia is located on the dorsal part, the kidneys are in the upper part of the body, and the brain is located near the esophagus.

Interesting!

Daphnia magna’s heart rate reaches 180 beats per second. Weak heart contractions indicate a painful condition of the crustacean.

Water fleas in the photo, even if they belong to the same species, may vary in color. The color of Daphnia depends on how rich in oxygen the pond is. With its excess, they are light yellowish or gray in color. If oxygen deficiency is observed in the reservoir, the body becomes dark brown.

What do water fleas eat?

In the natural environment, crustaceans feed on the simplest organisms: ciliates, bacteria, fungal spores, free-floating algae. In the summer, they can be found in flowering water, abundant in phytoplankton. In winter, detritus is the source of nutrition for water fleas.

With the help of the legs, the crustaceans make rhythmic movements and create a water current. The bristles located on the chest legs filter the food. Then it enters the groove, after which it is redirected to the esophagus. Due to its nutritional characteristics, a Daphnia culture is often planted in an aquarium to purify water from algae.

Interesting!

For one day, one individual is able to filter from 1 to 10 ml of feed in water and consume an amount of food that is 6 times its own weight.

Propagation of water fleas

In the presence of a food base, the eggs of a female develop without male intervention. Embryos develop in a special chamber located under the sink. You can see them in the body of a female even without a magnifying glass. The number of juveniles varies from 5 to 10. Over the course of her life, the female is able to give life to 100 crustaceans. During the period in the chamber, the embryos are molted.

Interesting!

Generation of a female during parterogenesis always has one gender. In summer, ponds overrun young females, and in the autumn, males develop predominantly.

3-4 days are enough for a newborn female to be able to replenish the reservoir with her offspring, and given that in the hot period exclusively female individuals are born, population growth is rapid.

The process of bisexual reproduction is possible with a decrease in temperature and an insufficient amount of food. Embryos are in the chamber and protected by a dense chitinous cover. During molting, the female drops the capsule with eggs, and she either sinks to the bottom or swims in the upper layer of water. The dense shell maintains the viability of the embryos during freezing, high temperatures, in toxic solutions.

The benefits and harms of water fleas

Contrary to the erroneous opinion, Daphnia are not able to bite a person, their mouth apparatus is absolutely not suitable for this. Water fleas are used as food for aquarium fish. Depending on the species, nutritional conditions, crustaceans contain from 50 to 70% protein. They are given to fishes in fresh, frozen or dried form.

You can catch “live food” in any body of water by means of a net or establish production at home. Water fleas in the aquarium will serve not only as food, but also purify the water.

The harm of crustaceans lies in their allergenicity. During flowering, pollen is carried by the wind and into water bodies. Daphnia during the filtration process passes it through itself, as a result of which the allergen accumulates in them. During the drying process, pollen stays and provokes strong allergic reactions, which are mistaken for bites.

Signs of an allergy to daphnia:

• the appearance of a rash on the body, similar in nature to hives;
• severe itching;
• sneezing, nasal congestion;
• labored breathing;
• lacrimation, eye inflammation.

Only a doctor can perform an accurate diagnosis on the basis of a skin test. Antihistamines, inhalers are prescribed depending on the severity of the symptoms.

Growing Water Fleas

To provide the inhabitants of the aquariums with ecologically clean food, daphnia is grown at home:

1. First of all, it is necessary to prepare a tank in which crustaceans will breed. It can be any plastic container suitable for food, plastic bottles from under drinking water are often used.
2. Crustaceans are not particularly demanding on the composition of water. The main thing is that there should be no impurities of salts or metal compounds in it.
3. Yeast and green algae are used as food. The latter are actively developing in the sunlight. It is enough to put a bottle filled with water with a microalgae culture in a warm place, as soon as after 10-14 days it will be possible to feed the water fleas with their own hand grown food.
4. In order for crustaceans to actively reproduce, it is necessary to create favorable conditions for them: a temperature of 23-25 \u200b\u200b° C and 24 hours of daylight.
5. Periodically, the Daphnia culture and water are renewed.

The highest nutritional value of fresh water fleas. When frozen, they lose some of the enzymes and amino acids.

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

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Description

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

Daphnia spend the bulk of their lives in the water column, move in sharp leaps, and wave their antennas, which are covered with special bristles. Many types of daphnia can crawl along the bottom or walls of tanks under the stimulus of the flow of water, which create chest legs. In this process, the antennas remain stationary. In the summer, daphnia lives in lakes, rivers and ponds with flowering water, where the level of high accumulation of cyanobacteria. These crustaceans are very prolific, and breed rapidly.

Breeding process

The ability to self-reproduce without the need for multi-sex reproduction, when the offspring entirely inherits the parent's genotype, is parthenogenesis. Daphnia can breed at high speed, shortly after it is poked from eggs. Under natural conditions, in the last months of spring, summer and autumn, regardless of temperature, nutrition, these crustaceans breed by the method of parthenogenesis, and give birth to about 10 larvae. During these seasons, only females live in ponds.

Embryos can be seen through the mother's body without the use of a microscope. The females of the next generation will be able to prepare for parthenogenesis on the 4th day of life, and give birth to nauplii every three days. Over the life cycle of a female, 25 generations of crustaceans can reproduce; in general, she will give birth to about 100 fry. If there is not enough food, caviar can develop in males, and at this time the females produce caviar, which must be fertilized. It will develop into tiny embryos that hibernate and cover with a saddle shell called ephippia.

With such a metamorphosis, daphnia is able to survive the harsh environmental conditions, even dried up water bodies or its glaciation. Females that appear for the formation of ephippia are easily distinguished - they have a dark spot on the body in the back of the trunk. Partogenetic broods do not. With the resumption of favorable environmental conditions, a generation will emerge from the eggs that will give birth exclusively to females, and all born males will die until adverse conditions resume.

How to catch daphnia?

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

Look at catching daphnia from the pond.

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

You can catch fish food in small puddles, but it’s difficult to use a standard net in them. Use a net with a short cone so that it does not cling to the bottom and does not raise turbidity. To prevent hydra from catching with daphnia, catch them away from algae and aquatic plants to which hydra can be attached. Do not catch fish food in a pond located near industrial areas.

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

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

In the warm season, daphnia can be dangerous for the owners of aquariums. In summer and spring, crustaceans feed on pollen from flowering plant species, which are introduced into the reservoir by wind. Crustaceans caught during these seasons during feeding of fish cause painful allergic reactions in humans. It is in the warm seasons that crustaceans are saturated with pollen, which is why there is an opinion that aquariums are harmful to health.

See how to grow daphnia at home.

How to breed at home?

Daphnia can be grown at home in a 20-liter container made of glass or plastic. Cannot be used to grow containers that can release toxic substances. If you use metal containers, then they must be made of stainless steel. Aluminum oxides form a film that can be toxic. Daphnia is demanding on the oxygen content in the water, so the bottom area of \u200b\u200bthe tank should be wide. In the summer, you can put a tank of 50 liters on the street, where the future fish food will be grown better.

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

Daphnia is susceptible to muddy and dirty water, but there should be enough oxygen in the water; install a compressor in the containers for keeping and diluting. These crustaceans form hemoglobin, so that even in the absence of oxygen-enriched water, they can survive, but not for long. But they do not tolerate aeration with small air bubbles, since they can destroy them. Home-grown fish food will be safe and beneficial for fish.

Daphnia or Daphnia is known to many under the name "water fleas" from the genus of planktonic crustaceans. This family belongs to the superorder of Cladocera or Cladocera. Water flea is a very small insect with a body length of not more than six millimeters. Many inhabitants quite often attribute to these crustaceans bites, which are outwardly similar to flea ones, but are not.

View description

Water fleas have very interesting structural features. Their whole body is clad in a leathery, double-skinned shell, which ends with two hooks of a specific horn type. One spherical eye is characterized by significant mobility and consists of a large number of small eyes. In numerous photographs taken while observing these living things through a microscope, you can see all the features of such an eye.

Water flea refers to the type of typical planktonic crustaceans that spend a significant part of their 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 with a body length of not more than six millimeters and a male having a length of only two millimeters are clearly distinguishable. Individuals during the neonatal period have microscopic dimensions. The ripening period lasts two weeks. Standard masonry consists of three dozen eggs that are laid by females every two weeks. The average life span of individuals does not exceed three months.
• Daphnia Puleks.  Females of this species have a body with a length of not more than four millimeters. The body of males is half as much. This species is incredibly prolific, and the clutch occurs every five days and consists of fifteen eggs. The average lifespan can last a month and a half.

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

To get rid of fleas, our readers recommend the Pest-Reject repeller. The device is based on the technology of electromagnetic pulses and ultrasonic waves! Absolutely safe, environmental remedy 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 immediately to several continents.

These crustaceans are least found in equatorial areas. The most populated areas by Daphnia include subtropics and temperate latitudes. At present, there is a significant expansion of the habitat of water fleas, which is due to human activity.

Power Features

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

The method of nutrition is filtration.  Of no small importance is the ability to create water currents through rhythmic movements that are performed by the pectoral legs. For filtering food, special fans are used located on the filter-type bristles. Such an organ is located on the sites of endopodites from the third and fourth pairs of thoracic limbs.

When large particles that get stuck in the apparatus for filtering get in, a special organ is activated, represented by a post-abdomain and its claws. The filtering fans serve as the transmission link of the food to the abdominal food groove, from which it moves to the maxilla and mandibles. The final place 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 of the water fleas. Any organs with which bites can be applied are absent in daphnia. The lip is equipped with salivary glands, which include giant polyploid cells. The salivary secret is gluing food particles into a single lump. An adult consumes almost six hundred percent of its own weight per day.

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 certain harm to humans, which is associated with a high degree of allergy to these crustaceans.

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

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

• lacrimation
• conjunctivitis;
• dryness;
• nasal sinus congestion with difficulty breathing;
• runny nose;
• involuntary sneezing.

At the next stage, urticaria and eczema may appear, which are mistaken and taken for bites. In addition, significant skin seals, which are also one of the symptoms of allergies and are capable of causing severe itching, are slightly similar to flea bites.

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

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

• antihistamines;
• inhaled type of modern corticosteroids;
• anti-leukotriene type drugs.

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

How water fleas breed (video)

Daphnia bites are nothing more than the imagination of most ordinary people. 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.

The body of Daphnia is compressed laterally and everything is covered, with the exception of the head, by a bivalve shell (carapace). Inside the shell, the body is placed freely, attaching to it only with the front part.

A brood (germ) chamber is located between the walls of the shell flaps and the dorsal surface of the animal in females. The edge of the shell on the dorsal side is elongated into a long spine (spina). The head is bent to the ventral side, the frontal part is elongated in the rostrum directed down and back. The large median eye, formed by the fusion of two complex eye embryos, is equipped with special muscles, which determines its mobility inside the eye chamber. Some Daphnia species also have a small unpaired peephole. Short antennules, which are sensory organs, articulated in females motionless with head behind rostrum; at the end they carry a bunch of sensitive bristles.

Antennas, which are the only organ of movement, are well developed and consist of a large protopodite and two branches, the outer or exopodite, and the inner, or endopodite, armed with long feathered swimming setae. Strong antennas are visible inside the antennas. Each antenna is driven by three abductors, three adductors and one levator; the first two abductors and the levator, with their conspicuous fan-shaped extended ends, are attached to the chitin of the dorsal part of the head. The rise of the antenna occurs due to the reduction of adductors and levator, abductors are their antagonists.

Mandibles, clearly visible in living organisms by peculiar movements, lack a palp on the inside with a large chewing surface consisting of chitinous plates armed with spines. Maxillules are reduced. Maxilla is completely absent. 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 back of the brood chamber; behind these outgrowths is a pair of feathered swimming or tail setae. The posterior abdomen behind the caudal setae is called the postabdomain, or cauda. It is bent under the body of the body so that its upper, or dorsal, edge, on which the anal opening opens and the anal teeth are located, becomes like a lower edge; at the end of the postabdomain, there is a furka formed by two strong and slightly curved claws called furcal, or caudal, claws.

The mouth, bounded above by the upper lip, and on the sides by mandibles, leads into a short esophagus, passing into a long middle gut, of the same diameter throughout its length; in the front of the middle intestine are paired hepatic outgrowths that look like short and curved blind appendages located in the head.

The heart has the form of a rounded sac with one pair of lateral spines. Heart contractions are performed 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. Osmotic blood pressure under normal conditions is equal to two to four atmospheres. This circumstance is of great importance for maintaining the shape of the body and the elasticity of the limbs (turgor limbs).

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

The organs of excretion are paired armor-clad (shell) glands located in the thickness of the shell cusps, between the outer and inner layers, and are clearly visible after the cusps are separated from the body of daphnia.

A well-marked brain consists of two merged halves. From its front part, nerves depart to the complex eye, and on the underside there is often an unpaired (nauplii) eye.

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

All embryonic development of juveniles proceeds in the brood chamber between two molts. Daphnia form parthenogenetic and latent eggs. The latter are enclosed inside the highly modified and dark-colored upper part of the shell cusps, forming the so-called ephippia (saddle).

Daphnia males differ from females in the absence of a brood chamber, the presence of large and mobile antennals, and other weapons of the legs of the first pair.

A — B — Daphnia magna, female (A), male (B), female postabdomae (B), D, D — Daphnia longispina, female (G), female postabdomain (D); B - Dap cucullata, female; F, 3 - Daphnia cristata, female (F), antenna (3).

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

The caudal claws at the base are armed with large spikes.

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

Indented Postabdomain Upper Edge - D. magna

Caudal claws devoid of large spines at base

Unpaired peephole is present - D. longispina

Unpaired peephole missing

The rostrum is sharp; the setae of the antennae do not extend beyond its end - D. cristata

The rostrum is dull, the antennae bristles go beyond its end - D. cucullaia

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