Copepods (Coreroda). Copepoda A species of planktonic crustaceans from the subclass Copepoda

Herbivorous copepods - Calanoida

Copepods (Copepoda) - the largest and most diverse group of crustaceans. Currently, they include 3 orders (kalanoids, cyclops, harpacticides), 210 families, 2300 genera and more than 14000 species, and this, of course, is not the full number of organisms that inhabit the seas and continental waters, transitional zones between water and land, or living in symbiotic relationships with other animals. They are the most numerous group of multicellular animals on earth, outnumbering even insects, which include large quantity species, but fewer individuals!

Copepoda are mobile, frisky and relatively large planktonic organisms. With the help of antennae and pectoral legs, striking them like oars, they "fly" in the water column. Their body is spindle-shaped with a clear division into two parts: the cephalothorax and the abdomen, which ends with a furka resembling a fork. An unpaired eye is located on the head, for which one of their most well-known groups to aquarists bears the name of the Cyclopes - after the mythical one-eyed giants. Most copepods are predators, attacking even smaller animals. But there are also herbivorous forms - kalanoids ( Calanoida), which have a larger cephalothorax and a shortened abdomen (see photo). Their anterior antennae are very long (sometimes more than the length of the body) and serve as the main organ of locomotion. They feed mainly on algae.

Some species of cladocerans are characterized by cyclomorphosis. Many species are found only in the period of open water, laying resting eggs for the winter - ephippia, from which in the spring, when the water temperature becomes acceptable, juveniles appear. They also use this during their life in water bodies that dry up: they are in the form of an embryo in the epippia until it rains.
Zooplankton lives in all water bodies. In stagnant waters, the zooplankton community - zooplanktonocenosis - is richer both in terms of the number of species and abundance. Cladocerans, as a rule, do not tolerate the current, therefore they prefer lakes, ponds, puddles, reservoirs, but rotifers better withstand dizzying pirouettes in the flow of water, therefore, in rivers, springs, plankton consists mainly of them.

Zooplankton is of particular importance in lake ecosystems, where its abundance and biomass reach significant values. In rivers, communities of planktonic invertebrates form in deep-water sections of the channel with slow flow, in chickens, floodplain reservoirs. On stretches and rifts where there is no zooplankton as such, planktonic invertebrates are found in drift and benthos.

Zooplankton and benthos are the main communities of invertebrates that ensure the normal functioning of aquatic ecosystems, their self-purification, and are the food base for many fish species. Zooplankton usually make up three systematic groups invertebrates: rotifers (Rotatoria), cladocerans (Cladocera), copepods (Copepoda). The same taxa of invertebrates are also present in the benthos, but due to the specifics of the generally accepted selection of benthic samples, as a rule, rotifers are not taken into account in benthic communities. Most species of crustaceans live both in the water column, being an integral part of zooplankton, and at the bottom of reservoirs, in benthos. So most kalanoids ( Calanoida) throughout their lives, except for the stage of resting eggs, lead a planktonic lifestyle; cyclops (Cyclopida) also inhabit the water column, and are a component of microzoobenthos; harpacticides ( Harpacticoida) are considered exclusively benthic animals, but are quite common in plankton. Therefore, speaking about the biodiversity of zooplankton organisms and their knowledge, we mean the diversity and knowledge of planktonic and benthic rotifers, cladocerans and copepods.

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copepods

rice. 1 Copepods Of the copepods (Copepoda), aquarists are best known for cyclops and diaptomus (Fig. 1), which are usually combined because of their external similarity under common name Cyclops. The body of the crustacean is up to 5.5 mm long, divided into segments and has forked processes covered with hairs at the end, which, together with two pairs of antennae, . extending from the head of the body, facilitate soaring in the water. In cyclops, the front pair of antennae is short, and they move in jumps in the water, in diaptomuses they are longer, and after the jump, the crustaceans slowly hover in the water. The crustaceans are separate sexes; in fertilized females of the cyclops, under a microscope, one can see in the back of the body two bags filled with eggs with developing larvae in them, unlike diaptomus females, which have one bag. The larvae hatched from the eggs - nauplii, are completely different from them. adult crustaceans. Diaptomuses are gray or gray-green in color, and their body is covered with a pretty hard shell, "and they are less willing than cyclops to be eaten by fish. The color of cyclops depends on the type of food they eat and can be gray, green, yellow, red or brown. Cyclops inhabit the coastal strip of water bodies, diaptomuses keep in open water. The crustaceans feed on the smallest aquatic organisms: suspended algae, ciliates, detritus, etc. They catch crustaceans with a net made of cloth N2 28-32, and nauplius - from cloth N2 64-76, starting from spring, when the water warms up to OC, and until February. The net is immersed in water and moved in the form of a lying figure-eight, and the curves are drawn without pressure and smoothly, and the intersecting straight lines - with pressure. With this movement of the net, a whirlpool is created that sucks the crustaceans into the net. transport a large number of crustaceans are better on wooden frames with a fabric stretched over them. After laying the crustaceans on the fabric, the frame is quickly lowered into the water and then pulled out. which provides a relatively uniform layer of crustaceans, which should not exceed 3 mm. The frames are wrapped with a damp cloth and transported home. It can also be transported in vessels (enamelled, glass) with water. Houses of crustaceans, if necessary, are calibrated in size and, after removing the dead, they are stored in a cool and dark place (possibly in a refrigerator) in a vessel with the largest possible surface area with a small layer of water (preferably 3-5 cm). If stored in a glass jar with a high layer of water, then aeration is needed. Dead crustaceans must be sucked daily from the bottom with a hose,. Crustaceans can be frozen and dried. When feeding fish fry with nauplii, care must be taken and only as much as the fish can eat. because nauplii grow faster than fry and, remaining uneaten, can attack them. N. Zolotnitsky /4/ recommends breeding Cyclopes in an 01e-blowing way: "On a tub of water" one should put no more than a teaspoon of pigeon manure, and no more than a tablespoon of cow's manure, otherwise the mixture may ferment from the excess and prevent reproduction In addition, cow dung must certainly be fresh, since a lot of larvae of various insects develop in the stale, which will exterminate the cyclops: Finally, a tub with such water and cyclops should be placed in a sunny place and the water temperature should be not lower than 13 C, because otherwise the cyclops will burrow into the silt and not give birth.

CRASHES BRACHANICAL.

The cladocerans (Clado-cera) are grouped together by aquarists under the common name Daphnia. The body, strongly compressed laterally, in most species is covered with a bivalve chitinous membrane. There are two eyes on the head, which in fully developed specimens merge into one compound eye. In many species, there is another simple eye next to it. Split antennae depart from the head, striking with which the crustacean moves up with a push, and then slowly lowers.

Rice. 2. Branched crustaceans
1 - daphnia magna, 2 - daphnia pulex, 3 - daphnia longispina, 4 - simocephalus, 5 - ceriopaphnia, 6 - mine on, 7 - bosmina.
8 - hidorus. In summer, in warm weather, in the brood chamber of the female, unfertilized eggs (50-100 pieces) are formed, from which only females emerge, which soon leave the mother's body. Then the female molts and new eggs develop in her again. Juveniles also give offspring after a few days. This leads to a rapid mass reproduction of crustaceans, during which the water seems to be painted in a rusty color. With the onset of cold weather, at the end of summer and autumn; males appear from some eggs, and females begin to form eggs, which can develop only after fertilization by the male. these fertilized, hard-shelled eggs - ephippia, float or sink to the bottom and can tolerate desiccation and frost, preserving the continuation of the species during adverse conditions. Heat and moisture awaken them to life, out. eggs appear females, and the cycle begins again. Crayfish live in various reservoirs, ponds, lakes, ditches, water pits, etc. They feed on plant plankton, bacteria and ciliates, which are sucked in by water currents created by the movement of their legs. The most common are the following crustaceans(Fig. 2): large daphnia magna (Daphnia magna), up to 6 MM;
crustaceans medium size, up to 4 MM: daphnia pulex (Daphnia pulex), daphnia longispina (Daphnia longispina), species of the genera Simocephalus (Simocephalus) and ceriodaphnia (Ceriodaphnia);
small crustaceans, up to 1.5 MM: species of the genera Moina (Motya),
Bosmina (Bosmina) and Hydorus (Chydorus). They catch daphnia with a net made of NQ 7-70 fabric, depending on right size fish food. You can fish with a net made of N!1 70 fabric, and then calibrate. The net is immersed in water and moved in the form of a lying figure-eight, assuming the curves are carried out without pressure and smoothly, and the intersecting straight lines - with pressure. With "such a movement, a whirlpool is created that sucks the crustaceans into the net. They are caught from April to the end of October (sometimes later) at the shore protected from the wind or from the windward side, early in the morning or on quiet warm evenings before the sun comes out and also in cloudy weather.It is better to transport a large number of crustaceans on a wooden frame with a fabric stretched over them.After laying the crustaceans on the fabric, the frame is quickly lowered into the water and immediately removed, which ensures a relatively uniform layer of crustaceans, which should not exceed 3 mm The frames are wrapped with a damp cloth and transported home.It can also be transported in vessels (enamelled, glass) with water.Houses of crustaceans, if necessary, are calibrated in size and, having removed the dead, stored in a cool and dark place (can be in refrigerator) in a vessel with as much surface area as possible and a small layer of water (preferably 3-5 cm). If stored in a glass jar with a high layer of water, then aeration is needed. Dead crustaceans must be sucked daily from the bottom with a hose. Crustaceans can be frozen, dried or salted.
for salting, the bottom of the glass jar is covered with salt with a layer of 25 MM, crustaceans are placed on it with a layer of 50 MM, then again a layer of salt with 25 MM, etc. The jar is closed and stored in a cold place. Before feeding the crustaceans to the fish, they are thoroughly washed in a net. The stomach of crustaceans is constantly filled with plant foods, so they are especially useful for fish that need plant feeding. The chitinous shell of crustaceans is not digested and serves as a valuable ballast substance that stimulates the work of the intestines of fish. Bosmins, which are part of live dust, sometimes have such a hard shell that the fry cannot cope with it and spit out crustaceans. Moina is very good for feeding young fish.

Several recipes for breeding crustaceans developed by amateurs:
1. Daphnia magna, female up to 6 mm, male up to 2 mm, larva 0.7 mm. Ripens within 4-14 days. Litters in 12-14 days. Clutch up to 80 eggs. Lives 110-150 days.
Daphnia pulex, female up to 3-4 mm. Litters in 3-5 days. Clutch up to 25 eggs. Lives 26-47 days.
Moina (red crustacean), female up to 1.5 mm, male up to 1.1 mm, larva 0.5 mm. Ripens within a day. Litters every 1-2 days, up to 7 litters, up to 53 eggs. Lives 22 days.
Vessel made of glass or plexiglass. Water: 20-24 °C (for washing 26-27 °C), dH 6-180, pH 7.2-8. Weak aeration that does not raise dirt from the bottom, weak light for at least 14-16 hours a day.
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Feed: baker's yeast, frozen to . brown and diluted 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 food 2-3 times a week. The optimal density of crustaceans is 100-150 pieces ll. Catch 1/3 of juveniles daily, 1 time within 5 days for moins AND AT 10-15 DAYS for daphnia, do the culture again, cleaning the vessel from dirt and changing the water. 2. Daphnia magna and pulex.
Vessel made of glass or plexiglass, not less than 3 l. Aquarium water, 18-25 Os. Strong lighting for the development of algae. Dried elodea - lettuce or nettle leaves grind into powder, strain through cheesecloth and dip in water. When the water turns green, add crustaceans. Re-arrange once every 10-15 days.
Vessel made of glass or plexiglass. Water from a reservoir, where the crustaceans were taken from, or aquarium water. 20-24 Os. Weak aeration. Lighting for at least 14 hours. Food: stale blood (0.5-2 cm3 per 1 liter of water), blood or meat and bone meal (0.5-2.5 cm3 per 10 liters of water).

These small crustaceans, which aquarists feed to fish, are the main and most numerous representatives of aquatic metazoans. In addition, copepods are one of the main links in the food chain, the state of which ultimately affects our health. Their abundance and species diversity constitute an important part of the planet's biosphere. The biology and life features of copepod mini-crustaceans will be discussed in this article.

Free-living crustaceans are one of the most important components of zooplankton in salt and fresh waters. They make up the vast majority of the food supply for most fish and some marine mammals, which is called the generalizing word "krill". The usual food chain of the seas and oceans looks something like this: marine phytoplankton - copepods - herring - dolphin.

small crustaceans

Sizes of copepods range from 1 to 30 millimeters. Like all crustaceans, their body consists of three sections - the head, chest and abdomen. Respiration is carried out by the entire surface of the body, there are no gills.

On the head is the mouth apparatus (mandibles), simple eyes and two pairs of antennas:

• Single-branched antennules are jointed formations that participate in movement and perform the functions of sensory organs.
• Biramous antennules. Their main function is to provide water flow for swimming and feeding.

segmental body

On four segments of the chest are the main swimming legs of the crustacean - flattened and similar to oars, for which these animals got their name. The fifth segment contains modified limbs, which in some representatives of copepods play a role in sexual reproduction.

The abdomen of 2-4 segments is usually devoid of limbs and ends with paired movable appendages. Most species are characterized by sexual dimorphism, which is expressed in the number of segments of the abdomen, the structure of the limbs and the shape of the antennae.

Growth, development and fitness

Copepods are small in size and have outgrowths that increase the body area - such features allow these planktonic animals to stay in the water column at no extra cost. This is facilitated by a thin chitinous cover and reserves of fat, which accumulates in special fat drops and often gives color to these crustaceans.

When required abrupt change position of the body in the water column, they swim with the help of limbs or make jet jumps, folding their body in half.

Representatives of almost all types of copepods are dioecious organisms. Despite the outward simplicity, mating in these crustaceans is preceded by complex sexual behavior. In the process of mating, the male transfers a spermatophore (special bag) to the female's abdomen; fertilization of eggs can be both external and internal.

The larval form (nauplius) emerges from the eggs, which, after several molts, turns into an adult crustacean.

The strongest

If you think that the most powerful animals live on land, you are wrong. Recent studies show that small copepods can be considered the strongest. These crustaceans are capable of moving 500 times their size in 1 second. Their small legs develop a power of movement that is 10 times greater than that of other animals.

As you know, copepods also make jumps. The speed that they develop at the same time is 3-6 km / h. Few? This is comparable to if a person of average height could run at a speed of several thousand kilometers per hour.

The main component of plankton

About 20-25% of plankton are representatives of this particular group of crustaceans, united in 3 orders:

Food for aquarium fish

Cyclops and diatoms are the most famous representatives these crustaceans that are fed to aquarium fish. This is a high protein food for fry and adult aquarium inhabitants. At the same time, the nauplii of the Cyclopes are the most nutritious. But do not forget when feeding aquarium fish that cyclops are predators and grow quite quickly. Therefore, from food for fry, they can turn into predators that attack small fish. That is why experienced aquarists do not feed their pets with live food, but freeze it first.

Depending on what the cyclops ate, crustaceans are red, brown, green, gray. This property of accumulating dyes in your body is also used to give a brighter color. aquarium fish.

Value in nature

These small crustaceans form a key link in the food chain. marine ecosystems. Modern research show that the reduction of krill in ocean waters (according to some estimates, it has amounted to 80% since 1976) threatens the existence of not only many fish species, but also penguins, seals and even whales.

In addition, copepods, together with other benthic saprophytes, provide water purification from corpses and waste products. Planktonic crustaceans purify water from mineral suspension, contribute to its transparency, and therefore increase efficiency plant plankton. And in the end, it is they who participate in the enrichment of the atmosphere with oxygen and the absorption of carbon dioxide from it. This is how small crustaceans are built into a system common to the planet that regulates the climate and the state of the atmosphere.

And interstitial fauna are less common in plankton. The structure and lifestyle of free-living representatives of copepods are mainly considered below.

There is the World Society of Copepodologists. World Association of Copepodologists), which publishes the newsletter " Monoculus copepod newsletter».

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  The body of copepods is divided into three tagmas: head - cephalosome (in copepodology it is sometimes called cephalothorax, cephalothorax), chest (thorax) and abdomen (abdomen). At the same time, many copepodologists call the telson (anal lobe) the last abdominal (anal) segment.

  The body of copepods can "fold" in half, curving in the sagittal plane. In this case, the boundary between the functionally anterior part of the body (prosoma) and the functionally posterior part (urosoma) in cyclopoids and harpacticids passes between the segments of the thorax, which bear the fourth and fifth pairs of legs. These groups are united under the name "Podoplea" - "foot-belly". In kalanoids, the border between the prosoma and urosoma passes behind the segment bearing the fifth pair of legs, therefore they are called "Gymnoplea" - "blue-bellied". This character, which correlates well with other structural features, is given a high taxonomic weight, and Podoplea and Gymnoplea considered as taxonomic categories (in modern classifications copepods - like superorders).

  Head and its appendages

  The head bears the first one-branched antennae (antennales, mustaches), the second two-branched antennae (antennae), mandibles, first maxillae (maxillae), second maxillae (maxillae) and maxillipedes (mandibles) - appendages of the first thoracic segment fused with the head. In representatives of most families of harpacticids and in some representatives of other orders, the next segment of the chest, which carries swimming limbs, merges with the head, which can be greatly modified in this case.

  On the head, between the mandibles, there is a mouth opening, covered in front of a large upper lip, and behind - a small lower lip. On the cutting edge head is a downward outgrowth - the rostrum, sometimes detached.

  Antennae I (antennales) are always single-branched. The number of their segments varies among representatives of different orders. So, harpacticids usually have 5-8 segments (up to 14 in males); most kalanoids have 21-27 segments; cyclopoids have 9 to 23 segments. In typical representatives, the relative length of the antennules differs: in kalanoids they are approximately equal to the body, in cyclopoids they are equal to the cephalothorax, and in harpacticids they are noticeably shorter than the cephalothorax. Antennae I are involved in locomotion and also carry sensilla.

  Antennae II are usually two-branched (in many cyclopoids they are single-branched), they are involved in creating water currents for swimming and feeding.

  The mandible is subdivided into a coxa, which forms a chewing outgrowth (gnathobase) with teeth and setae, and a palp, which initially consists of a basis, exo-, and endopod. Often the branches, and sometimes the base of the palp, are reduced. So, in many Cyclopes, only three setae extend from the mandible, which are considered to be the rudiment of the palp.

  On the chewing teeth of the mandibles of many marine copepods there are "crowns" made of silicon oxide, which help them to chew through the strong houses of diatoms.

  Breast and its appendages

  On the four segments of the chest following the mandibular segment there are biramous swimming limbs - flattened legs that serve as the main engines when swimming, for the presence of which the detachment got its name. The swimming limb consists of a two-segmented protopodite, the basal (proximal) segment of which is called the coxa, and the distal one is the basis, and two branches extending from the basis (sometimes it is believed that the protopodite includes another segment - the precox, which is weakly separated from the body). The outer (exopodite) and inner (endopodite) branches each consist of 2-4 segments and bear long setae covered with long thin outgrowths (setulae) and shorter spines.

  On the last segment of the chest is the fifth pair of pectoral legs, which usually do not participate in swimming and are greatly reduced or modified in many groups. In males of most families of kalanoids, they are sharply asymmetric. The endopodites of both legs are often rudimentary, the exopodite of one of the legs serves to transfer the spermatophore to the female's spermatheca during mating, and the larger exopodite of the other limb bears a long, claw-like curved spine, which is involved in holding the female. The structure and armament of the fifth pair of legs for cyclopoids and kalanoids is the most important taxonomic feature.

  Abdomen and its appendages

  The abdomen usually consists of 2-4 segments (excluding the telson). On the first segment of the abdomen are paired genital openings. In harpacticids and cyclopoids, it has a rudimentary sixth pair of legs; in kalanoids, it is devoid of limbs. The remaining segments of the abdomen do not bear limbs. On the telson there are two movable appendages - a fork, or furka (furcal branches). These appendages consist of one segment and are not homologous to limbs. The furca bears furcal setae, the length and arrangement of which is an important taxonomic feature.

  sexual dimorphism

  Typically, in females, the first and second abdominal segments fuse to form a large genital segment; no such fusion occurs in males, so males have one more abdominal segment than females.

  Representatives Cyclopoida and Harpacticoida males are usually noticeably smaller than females, have hook-shaped, shortened antennae I, which serve to grasp and hold females during mating.

  Many Calanoida females and males do not differ in size. Males have one modified antenna I, which is called the geniculate antenna. It is expanded in the middle part and is able to "fold in half"; like the Cyclopes, it serves to hold the female during mating.

  In some cases, sexual dimorphism is observed in the structure of almost any pair of limbs and body segments.

  Internal structure

  covers

  Nervous system and sense organs

  Central nervous system consists of the brain and the ventral nerve chain connected to it by the peripharyngeal nerve ring. An unpaired nerve departs from the brain to the naupliar eye and paired nerves to the frontal organ, as well as nerves to the antennules and antennae (the latter from the tritocerebrum). The subesophageal ganglion includes the ganglia of the mandibles, the first and second maxillae. The ganglia of the ventral nerve cord are slightly separated from each other. The entire abdominal nerve chain is located in the cephalothorax, it does not enter the abdomen.

  Nutrition

  Most free-living copepods feed on unicellular or small colonial algae, which they filter out in the water column, as well as benthic diatoms, bacteria, and detritus, which they may pick up or scrape off at the bottom. Many species of kalanoid and cyclopoid are predators that eat other types of crustaceans (juvenile copepods and cladocerans), rotifers, insect larvae of I-II age (including chironomid larvae and kulicid), etc. The copepodite stages of some freshwater cyclopoids climb into the brood chambers of Daphnia, where eggs are eaten.

  With more detailed study“filtrational” feeding of copepods with the help of high-speed microfilming revealed that many of them “hunt” for individual cells of algae, which they catch one by one. Algae-eating copepods store food energy in fat droplets found in their tissues, which are often yellowish-orange in color. In polar species, feeding primarily on diatoms, during the period of mass spring “blooming”, the volume of fat reserves can reach half of the body volume.

  Reproduction and development

  Mating is preceded by complex sexual behavior, which, apparently, is usually played important role both chemoreception and mechanoreception. Female copepods secrete sex pheromones, which are perceived by males with the help of chemosensory bristles (aesthetics) of the first antennae.

  When mating in most Calanoid families, the male first captures the female by the telson or furcal branches with the help of a geniculating antenna, then by the body area located in front of or immediately after the genital segment with the help of the legs of the fifth pair, while the male and female are usually located "head to tail " each other . Mating lasts from several minutes to several days.

  Free-living copepods have spermatophoric fertilization. Large, comparable in size to the size of the animal's abdomen, kalanoid spermatophores are transferred to the genital segment of the female during mating with the help of the left fifth leg of the male; at its end there are "tweezers" that hold the bottle-shaped spermatophore by the narrowed basal part.

  Role in ecosystems

  Copepods play an extremely important role in aquatic ecosystems and throughout the biosphere. Apparently, they have the largest biomass among all groups of aquatic animals and almost certainly occupy the first place in terms of their share in the secondary production of water bodies. As consumers of phytoplankton, copepods are the main consumers of the first order in the seas and fresh waters. Copepods serve as the main food for many other aquatic animals, from cnidarians and ctenophores to baleen whales.

  surface water oceans are now considered the largest sink of carbon dioxide (2 billion tons per year - probably about a third of anthropogenic emissions). In many ways, the absorption of excess carbon dioxide is provided by the vital activity of copepods.

  Many planktonic copepods feed at night in the surface layers of the ocean, and migrate to the depths during the day to avoid being eaten by visual predators. Their corpses, discarded exuvia and fecal pellets sink into deeper layers of water. This (like the breathing of living copepods that digest food at depth) contributes to the movement of biogenic carbon from the upper layers of the water to the bottom sediments. In addition, the formation of fecal pellets during feeding of copepods contributes to the purification of the upper layers of water from mineral suspensions. This increases the transparency of the water and hence the production of phytoplankton.

  Free-living copepods have certain signs of adaptation to life in the water. So, devices for “soaring” in the water column are small body sizes (0.1-3 mm), due to which the relative surface area of ​​​​the body increases, the presence of various outgrowths to increase friction against the water (antennae, furks, antennular outgrowths), thin covers body, storing fat in reserve in cells, which leads to a decrease in body density. This allows copepods to stay in the water column for a long time with little energy consumption. These organisms are characterized by bioluminescence, and representatives of many families of copepods glow in the dark due to the release of a luminous secret. Most free-floating copepods feed on unicellular algae, absorbing them through filtration, and detritus, bottom bacteria also serve as their food. Rare species some subgroups of copepods are predators. They eat insect larvae, other small crustaceans, their eggs.

  External structure

  In the body, a head, a chest, often merging into a cephalothorax, and an abdomen are distinguished. Two pairs of antennae are located on the head: the first are single-branched, the second are two-branched. oral apparatus It is a mouth opening covered by the upper and lower lips, and oral appendages (maxillas, mandibles). There are mandibles - appendages of the first thoracic segment, firmly fused with the head. The swimming limbs are attached to the second thoracic segment, which in some species is also firmly fused with the head, they are highly modified in different species.

  After the mandibular segment, there are four segments of the chest, from which two-branched flattened swimming limbs extend, which are the main elements in swimming. This feature of the structure was the reason for the name of the detachment "copepods".

  In the structure of the abdomen, 2-4 segments are distinguished. hallmark females - fusion of the first and second segments of the abdomen with the formation of the genital segment large sizes. The first segment has paired genital openings.

  Internal structure

  The nervous system is represented by the brain, the peripharyngeal nerve ring and the ventral nerve cord (within the cephalothorax). Digestive system consists of the esophagus, anterior and posterior intestine, ending in the anus at the posterior edge of the abdomen. Copepods have a heart but no blood vessels. The hemolymph enters directly into the body cavity and moves there due to bowel movements. Breathing is carried out by the entire surface of the body.

  The vast majority of copepods are dioecious animals. Characterized by sexual dimorphism. Some time after mating, the female lays eggs. The hatched larvae after several molts turn into adult crustaceans.

  The value of the copepods. These crustaceans play a significant role in food chains. Due to the largest biomass, copepods are the main consumers - consumers of phytoplankton. In turn, copepods are the main part of the diet of many aquatic animals - from hydroids to big fish and whales. Thanks to the vital activity of these crustaceans, the upper layers of water bodies are cleared of mineral suspensions, thereby increasing the transparency of water bodies and, as a result, increased development of phytoplankton. It is important that the absorption of excess anthropogenic carbon dioxide occurs precisely by phytoplankton, which is interconnected with the vital activity of copepods.