Crayfish live both in water bodies and on land.

crustacean classification

Crustaceans include crayfish, crabs, lobsters, shrimp, wood lice and other living creatures. There are even immobile life forms such as balanus and barnacles. In total, about 73 thousand species are known, which are combined into several classes.

Ancient and primitive branchiopods

Representatives of the class have several identical limbs that perform many functions at once. Animals move with the help of legs. In addition, with active repulsion, food filtered from the water sticks to the limbs, which is then sent to the mouth.

The branchiopods got their name because their limbs provide a respiratory function. They have a thin cuticle that absorbs oxygen from the water.

Daphnia is one of the smallest representatives of crustaceans.

The list of representatives of crustaceans of this class includes one and a half thousand species. The most well-studied of these are brine shrimp and daphnia. Both of them are planktonic organisms. Their food is carried out with the help of thoracic limbs, which filter phytoplankton from the water. Artemia are found in shallow sea waters and mineral lakes, while daphnia inhabit continental reservoirs and calm rivers. Basically, these organisms are used as food for aquarium inhabitants.

Ground cephalocarids

The class has only 12 species. They are united by the habitat - all representatives live on the seabed or in the ground freshwater objects of the hydrosphere. The size of cephalocarids is small - only 2-3 mm.

A large head stands out on their body, partially fused with proportionally developed thoracic segments. Antennas, mandibles and four legs are primitively located on it. The representatives of the class have no eyes. The limbs on the body perform the same functions as those of the branchiopods.

Cephalocarids feed on the remains of plant and animal organisms or their secretions suspended in water or settled to the bottom.

The first representative, subsequently named Hutchinsoniella macracan, was found on the Atlantic coast at Woods Hole by the American zoologist Sanders.

Large higher crayfish

The largest class in terms of numbers includes more than 35 thousand species. Geologists have found the remains of its representatives, stored since the Cambrian period.

Now higher crayfish are found in fresh and salty waters as well as on dry land.

On the head of these creatures are antennae and antennules, jaws of the mouth apparatus and eyes. In most of the species, the head is fused with several of the eight thoracic segments, so their forelimbs act as mandibles. The remaining biramous leaf-shaped limbs are located on six abdominal segments . In this class, representatives of crustaceans include:

Thus, higher cancers are found in various forms almost everywhere.

Small barnacles or ostracods

A class of small individuals with a non-segmented flattened body placed in a bivalve chitinous shell with patterns formed by protrusions. Ostracods have eyes, antennae, legs, a short abdomen, and jaws equipped with leg-shaped tentacles. Breathing is carried out by the entire surface of the body.

According to geological studies, earlier representatives of the class reached a size of about 9 cm, but now their growth does not exceed 6 mm, and more often does not reach 2 mm. They only live in aquatic environment, salty or fresh, are found at a depth of up to 5.5 km. They feed on the corpses of animals, and themselves become food for fish.

One of the most famous representatives of ostracods - Notodromus monachus. This millimeter-sized pale green organism is found in summer and autumn in fresh water. Also well studied is Cypris, distinguished by its unpaired eye and lack of circulatory organs.

Ostracods rarely exceed 2mm in size.

Blind remipedias

This class was officially considered extinct for two decades, but in 1979 its representatives were discovered in Australia, the Caribbean Sea and the Canary Islands.

Now remipedia is being actively studied. It has been established that their body is divided into the head and torso, which, in turn, consist of a large number of segments. The appendages perform various functions: antennae with bristles are responsible for the sense of smell, and the claw at the end of the maxilla injects poison into the body of victims when hunting. Recent studies have helped establish the composition of the secretions, which includes digestive enzymes and a neurotoxin present in spider venom. Individuals are blind, as they do not have eyes.

The behavior of remipedias is calm - they swim slowly, feed by filtering water currents. But some species are predatory. The most famous representative is the nectiopod.

Maxillopods or jawed

Orders of crustaceans that could not be attributed to any of the known classes were collected in the maxillopod taxon, therefore, a number of authors consider it garbage. Nevertheless, representatives of this class also have common features, for example, the absence of limbs on the abdomen and a reduction in the number of its segments.

In addition, all individuals have the same number of segments in different departments:

• on the head - 5;
• on the chest - 6;
• on the abdomen - 4.

The size of arthropods in this class is predominantly small. There are individuals that grow only 0.1 mm. The most famous representatives- cyclops and balyanuses. The first crustaceans are a few millimeters in size and live at the bottom or in the fresh water column, where they prey on unicellular and small multicellular organisms. Often they themselves become food for fish and fry. They got their name for an unpaired frontal eye.

Cyclopes are several millimeters in size.

Adult balanus are attached to hard surfaces and lead a motionless lifestyle. It brings great harm sea ​​vessels, as tons of such organisms can stick to them. Large sums have to be spent on cleaning the bottoms.

But some travelers appreciate the taste of balyanuses, which are also called sea acorns. They make soup and canned food.

Alternative version

Some databases do not adhere to the generally accepted classification. The group of maxillopods is not recognized in them and is divided into two superclasses, which, in turn, are formed into several subclasses. This makes it possible to systematize knowledge about animals to a greater extent. The main subclasses are as follows:

This classification is just another option for systematizing crustaceans. A single concept has not yet been developed, so the process is being delayed due to disagreements among researchers. There is an opinion that insects should also be included in the subtype. If this statement is accepted scientific community, the entire systematization will have to be reworked: to identify new common features and refuse to combine into a taxon based on the degree of relatedness of species.

Most Valuable Representatives

The most famous representative is the broad-toed crayfish, common throughout Europe. And although the population of this species declined sharply at the turn of the XIX-XX centuries. , in Russia it does not have the status of a vulnerable animal.

But three other representatives from the class of higher crayfish, which are endangered, are listed in the Red Book of the country, namely:

1. The mantis shrimp got its name from its bent forelegs. This animal has remarkable, brightly colored green color pincers. They possess powerful force strike, so that they can be successfully defended. The arthropod is a predator, moreover, quite aggressive. Two males fight for a female, inflicting severe injuries on each other.
2. The Japanese crab is found in Peter the Great Bay. The animal has a small size, not exceeding 10 cm. Females are usually slightly wider than males.
3. Deryugin crab, named after a Russian zoologist. It lives in the North Pacific Ocean. Outwardly, it differs from other crab-like ones by an asymmetrical abdomen and one reduced pair of walking legs. The animal has an unusual color - the shell is orange or greenish on top, the legs are brown, and the claws are bright red.

These animals are protected from hunting at the legislative level.

Sometimes doubts arise whether the fish is a cancer or an animal. The answer to this question is obvious: a group of arthropods has nothing to do with fish, except that the habitat makes them related. But representatives of both taxa belong to the animal kingdom.

CLASS HIGHER Crayfish (MALACOSTRACA)

For class crustaceans are characterized by new progressive features in comparison with the class of worms, the origin of which is associated with the class polychaete worms. Along with the division of the body into three parts, well-developed jointed limbs appear in the class of crustaceans (which, in general, gave the name to the type), the tubular segments of which are interconnected by means of movable joints. Such a complex structure gave crustaceans the ability to perform a variety of movements. In the course of evolution, the limbs of crustaceans were specialized to perform certain functions: movement (walking legs of cancer), respiration (gills), capture of prey (claws of decapods).

The appearance of the chitinized cuticle allowed not only crustaceans, but also other representatives of classes such as Arthropods to move to land. The chitinized cuticle protects the animal's body from drying out and mechanical injury. The development of the exoskeleton (which is the dense chitinous cuticle) led to the progressive development of individual bundles of striated muscles, which led to an increase in the animal's mobility and made it possible to perform even more complex movements.

All the evolutionary changes listed above have made representatives of the Arthropod type in general, and crustaceans in particular, quite competitive in comparison with other organisms less advanced in terms of evolution. Evolutionary metamorphoses have led the phylum Arthropods to intensive development.

The appearance of the cuticle limited the free growth of the body of the arthropod. Hence the natural need for regular molting arose. When the animal sheds the old cover, and until the new cuticle has acquired hardness, the body of the arthropod grows intensively. After hardening of the new cuticle, the arthropod is unable to grow until the next molt.

Let's take a closer look at the basics of the structure of crustaceans using the example of crayfish - one of the most famous representatives of the class of crustaceans. The body of representatives of crustaceans consists of the abdomen and cephalothorax, the head end of which bears five pairs of appendages. On the front of the head section - the acronome - there are organs of touch and smell in the form of a pair of antennules and another pair of longer antennas.

The three subsequent head segments have three pairs of limbs that act as mouthparts. The oral apparatus itself consists of the upper jaws (they are also called mandibles), the first and second lower jaws, called maxilla.

These segments, together with all eight thoracic segments, form a gnathothorax (jaw-chest), covered with a powerful dorsal shield - a carapace. The remaining free limbs are divided into several groups: three pairs of mandibles (involved in the feeding process), a pair of claws (serves for hunting, participates in the feeding process and performs a protective function), four pairs of walking legs and abdominal limbs.

The abdomen itself consists of six segments, each of which is represented by a strongly chitinized tergite - dorsal sclerite and sternite - abdominal sclerite (weakly chitinized semicircle).

The abdominal limbs - swimming legs - are called pleopods. It is thanks to the pleopods that the crayfish swims head first. In males, the first and second pair of these legs are transformed into copulatory organs - gonopodia, with the second pair retaining branching. Males differ from females in a slightly wider legs, as well as a whitish color of the entire body.

If we talk about the digestive system of crayfish, then it consists of the foregut, starting mouth opening and having a chitinous lining; divided into two parts of the esophagus (chewing part and filtering part), leading to the stomach; the middle intestine, into which the duct of the hepatopancreas opens (the digestive gland of crustaceans, which combines the functions of the liver and pancreas of mammals). The digestive apparatus of crayfish ends with an anus.

Sometimes in the region of the stomach of crustaceans, in pocket-like formations, it is possible to detect lenticular white "millstones" consisting of calcium carbonate and calcium phosphate. These formations serve to deposit calcium. They dissolve immediately after molting, and the stored calcium is used to impregnate the cuticle.

Cirrus gills located on the second - fifth pair of limbs are the respiratory organs of crustaceans. The gills themselves are located in paired gill cavities on the sides of the thoracic region. WITH inside the cavities are limited by the wall of the body, and with the outer one by the overhanging edges of the carapace (upper "shell"). Gill cavities open with gill slits.

The circulatory system of crayfish is represented by the heart and large vessels extending from it, from which blood flows directly into the body cavity. Then, through the venous sinuses, the blood enters the gills and, after being oxidized by oxygen dissolved in water, returns to the heart. An interesting detail: the blood of some higher crustaceans (for example, lobsters) has a bluish color. Such a kind of “sign of nobility” arises due to the blood pigment, which has copper in its composition. This pigment is involved in oxygen binding, playing the same role that hemoglobin plays in human blood. So some crustaceans, one might say, are "blue-blooded" aristocrats - in the truest sense of the word.

The nervous system of crustaceans has the form of a chain. The brain of the crayfish we are considering arose as a result of closerniya in the head of the ganglia. By the way, I note that for the first time in evolution, the brain appeared precisely in arthropods.

Surely, given the immobility of the cephalothorax, nature endowed cancer with eyes located on stalks and providing crustaceans with an excellent view around. However, this does not mean that crustaceans have the advantage of panoramic observation. The fact is that crayfish have a very complex (faceted) eye, which consists of many small eyes. At the same time, each of the eyes perceives only a small part of the surrounding space. That is why the overall picture of what he saw is, alas, a mosaic character.

In lower-organized crustaceans, the organs of vision are represented by a simple eye. Chemoreception of crayfish occurs indirectly through specialized cells located on the antennae, antennae, and limbs. And some crustaceans also have an organ of balance.

A pair of antennal glands is the excretory system of crustaceans. It is represented by small coelomic sacs connected by a canal with the bladder, which opens at the base of the antennae with an excretory pore. For the green color of the channel, excretory system called the green glands.

The development of crayfish is direct, although some types of crustaceans (mainly marine) also have indirect development. In conclusion of the story about crayfish, I will note such an important detail. Despite the progressiveness of all structural features, most land crustaceans, if they have not retained a connection with water (like, for example, crabs, whose larvae develop in an aquatic environment), then need elevated level moisture and, accordingly, live in a humid environment of wood dust or under leaf litter.

More interesting articles

SUBCLASS V. MALACOSTRACA

number of segments: 4 head, 8 thoracic and 6 abdominal (except for thin-shelled crayfish of the order Leptostraca; see below). The head either forms a single head capsule - a complex head, which, in addition to the acron and 4 head segments, includes the first segment of the chest (ref. Amphipoda, Isopoda), or is represented by a protocephalon (acron + antenna segment). In the latter case, the jaw segments of the head merge with several or all of the segments of the chest into a special section called the jaw chest. Abdomen with 6 pairs

Rice. 291. Nebalia Nebalia geoffroyi, male (according to Klaus):

/ - antenna, 2 - antennula, 3 - eye, 4 - transverse muscle, 5 - chest,

6 - testicle, 7 - heart, 8 - double shell, 9- abdomen, 10 -

telson, // - abdominal legs

limbs. The organs of excretion in the adult state, as a rule, are the antennal glands. The genital openings lie in the female on the 6th, in the male on the 8th thoracic segment. In development, the zoea larva is characteristic.

The Russian name of the subclass is not entirely successful, since some structural features, for example, the development of biramous limbs on all abdominal segments, are clearly more primitive than in other crustaceans. Probably, the higher crustaceans in the process of evolution developed as an independent branch independently of other subclasses; Obviously, each of the subclasses of Crustacea retained its own specific primitive features of structure and development.

The subclass Malacostraca, which unites over 14,000 species, includes 14 orders, of which only the main ones are considered below.

Detachment 1. Thin-shelled (Leptostraca). A small detachment of small marine crayfish, consisting of only 8 species, with some features of low organization. Leptostraca have 7 (not 6) abdominal segments; the head, thorax and part of the abdomen are covered with a gable shell, between the halves of which there is a transverse muscle (as in Ostracoda). In the adult state, they have not only antennal, but also slightly reduced maxillary glands. Representative Nebalia(Fig. 291).

Squad 2. Stomatopods (Stomatopoda). A small but peculiar detachment of sea crayfish. The body is elongated (up to 34 cm long), with a very long and powerful abdomen. There is a protocephalon. The first four thoracic segments are part of the jawbone. The anterior 5 pairs (especially the 2nd pair) of the pectoral legs are changed into grasping limbs. The last segment of the 2nd pair of legs is flattened from the sides in the form of a serrated blade and can, like a penknife, be inserted into a special groove of the penultimate segment. The gills are developed on the thoracic and especially the ventral limbs.

Adult stomatopods mostly lead a burrowing lifestyle at the bottom of the sea, the larvae are found in plankton. Stomatopoda live

predominantly in warm seas. The number of species known so far is about 170. Representative - mantis shrimp (Squilla oratoria; rice. 292) up to 20 cm long. In the Mediterranean Sea, as well as in the Pacific and Indian Oceans, there is a fishery for some large stomatopods used for food.

Rice. 292. Mantis shrimp Squilla oratoria(from Birshtein): / - antennules, 2 - antennas, 3 - eyes, 4 - outer scales; n antennas, 5 - primary head, 6- carapace, 7 - thoracic segments, 8 - abdomen, 9 - telson, 10 - last pair of ventral legs 11 - abdominal legs

Squad 3. Mysis(Mysidacea). Crustaceans, outwardly resembling small shrimp (p. 328), but this resemblance is superficial and is caused by a similar way of life, namely adaptation to swimming. The body length is on average from 10 to 20 mm. About 500 predominantly marine, rarely freshwater species are known.

There is a protocephalon. The composition of the jaw-thorax includes no more than three anterior thoracic segments. One anterior pair of thoracic legs is turned into mandibles. All thoracic limbs are biramous. There are no gills, gas exchange takes place through the wall of the carapace. Mysids feed on small particles of detritus, which are filtered out by the bristles of both lower jaws and mandibles.

Rice. 293. Split-legged crustacean mysis relicta(according to Sars)

The female carries the eggs in a brood pouch located on her chest. Juveniles emerge from the bag, not much different from adult animals.

The usual representatives of myzid include Mysis rslicta(Fig. 293), living in cold and clean lakes of the northern regions of the European part of the USSR, in Northern Europe and North America. The practical significance of mysids is great - they make up a significant share in the diet of some commercial and artificially bred fish.

Detachment 4. Cubes (Cspacea). Small (from 10 to 35 mm) crustaceans, in general close to mysids, but lead a burrowing lifestyle. Anterolateral angles of the carapace

Rice. 294. Female cumate diastylis goodsiri(according to Sars):

/ - front angle of the carapace, 2 - antennula, 3- chest nipples, 4 - abdomen, 5 - telson, 6 - chest, 7 - carapace

elongated forward, brought together and have small lateral openings that communicate the space under the shell with the external environment. In other places, the edges of the carapace fit snugly against the body. Burrowing into the ground, the crustacean exposes only the front end of the body with carapace holes through which water penetrates under the shell and washes the respiratory cavities.

The composition of the jaw-thorax includes 3 anterior segments of the chest, the limbs of which are turned into legs. The thoracic legs are mostly two-branched, the ventral limbs are partially undeveloped. The compound eyes are rudimentary or absent. The eggs are incubated by the female in a brood pouch on her chest. Development without metamorphosis.

Cubes are predominantly marine inhabitants, only a few live in fresh waters. Pure freshwater form Lamprops corroensis lives in lakes and rivers Far East. To. ordinary marine representatives include childbirth Cumopsis And diaftylis(Fig. 294). Cubes are the favorite food of some fish.

Squad 5. Isopods (Isopoda). A large (4500 species) thriving group of crustaceans, characterized by high plasticity of organization

The body is usually flattened dorsoventrally (Fig. 295). Body sizes range from 1 mm to 5 cm, only deep sea bathynomus reaches 27 cm. Isopods have a complex compact head, which, in addition to the acron and head segments, also includes 1-2 thoracic segments. The limbs of the latter are turned into leg-jaws. On the head are large compound eyes. The carapace is absent; thoracic segments bear single-branched walking legs. The abdomen is shorter than the thorax; in most cases, all or part of the abdominal segments are fused with the anal lobe. Five pairs of anterior abdominal legs serve for breathing; they consist of a short base and two broad, leaf-shaped gill branches that point backwards

and stick together like the pages of a book. The exopods of one pair of ventral legs form a strong cover that covers all the gills. This structure of the respiratory apparatus allowed some representatives of Isopoda to adapt to life on land. An example is woodlice, breathing oxygen dissolved in a thin layer of moisture covering the gills. Some woodlice, however, breathe atmospheric air; in such forms, on the exopods of the anterior abdominal legs, there is a deep protrusion of the covers, from which the respiratory tubes, blindly closed at the ends, called pseudotracheae, depart.

The body of amphipods is mostly laterally compressed (Fig. 297). The head, like that of isopods, is solid, 1-2 thoracic segments are attached to it. Faceted eyes. The carapace is missing. Legs of all thoracic segments

Among the representatives of Amphipoda deserve

references to sea fleas - Gammarus And Anisogammarus, masses inhabiting the tidal zone of many seas. The bottom of the continental slope of the northern seas is especially rich in amphipods. So, in the Chukchi Sea, about 40,000 individuals live on 1 m 2 of the bottom. The lake amphipod belongs to the usual freshwater amphipods - gammarus lacustris, widespread in the northern hemisphere (Fig. 297). In Baikal there is a fauna of amphipods found nowhere else (240 species).

The practical importance of amphipods is quite large, since they are a favorite food. various fish. In this regard, some freshwater amphipods were transferred and acclimatized in a number of lakes and reservoirs.

Order 7. Euphausiaceae (Euphausiacea)- a small detachment of higher crustaceans, numbering only about 80 species. These are planktonic inhabitants of the sea, outwardly similar to small shrimps (p. 328). They are characterized by the presence of a protocephalon and the jaw-thorax, which included all the thoracic segments, and the development of a carapace. Euphausia, like shrimps, have a number of similar adaptations for swimming in the water column. However, Euphausiaceae are easily distinguished from shrimps by the presence of free gills, not covered by carapace, sitting on the bases of the pectoral legs (Fig. 298). The latter are biramous and, unlike decapods, do not form mandibles and serve only for swimming.

Rice. 298. Euphausian cancer Euphausia pellucida(according to Sars)

Euphausiae are characterized by well-developed compound stalked eyes and organs of luminescence - photophores, especially in deep-sea forms. Usually there are 10 pairs of photophores located on the eye stalks, thoracic and abdominal segments. Euphausia are good swimmers, moving mainly with the help of strong ventral legs. Body sizes range from 7 to 96 mm.

The female lays eggs in the water or attaches them to the abdominal legs. A nauplius emerges from the egg.

Euphausian masses multiply in some areas of the sea, where they serve as food for various marine mammals and fish. Thus, in the Antarctic waters, concentrations of baleen whales are associated with mass breeding zones of the so-called krill - Euphausia superba. Mass species in the Barents Sea Thysanoesia raschii - food of herring, sea bass, cod and other commercial fish.

Squad 8. Decapods (Decapoda). This order unites large and in many respects the most highly organized crustaceans. There is a primary head - a protocephalon, bearing two pairs of antennae and stalked eyes. All segments of the thorax merge with the jaw segments of the head and are covered with a carapace. The front three pairs of pectoral legs are turned into maxillas! The first pair of walking legs are mostly claw-shaped. The thoracic limbs of the more primitive forms are biramous, rowing, while the majority are single-branched, because the exopodite disappears. The gills are located on the thoracic limbs, partly same on the sides of the body. The shape and structure of the abdomen in decapods are very diverse. In some cases, the abdomen is large, long, with well-developed legs that serve for swimming. The latter, however, in a number of forms are greatly reduced in size and no longer take an active part in the movement. In other cases, the abdomen loses part of the limbs, becomes soft and asymmetrical (hermit crabs). Finally, crabs have a very small, symmetrical, anteriorly bent abdomen that bears vestigial limbs.

Over 8500 species belong to the decapods. They are very widespread, occurring at all depths of the seas and oceans. The fauna of decapods is especially diverse in the shallow waters of tropical seas. Freshwater forms include crayfish and some crabs and shrimp. Some species of crabs and hermit crabs have moved to a terrestrial lifestyle.

Female decapods attach their eggs to their ventral legs and carry them until they hatch. For the most part, a larva emerges from the egg, which differs sharply from an adult animal, for example, in crabs and hermit crabs - zoea, and in lobsters - the mysid stage. Only in some lower shrimp the first larval stage represented by the nauplius. For freshwater and deep-sea forms, direct development is characteristic, when a miniature, almost formed animal emerges from the egg.

The practical importance of decapods is important, because many of them are a valuable food product. Crayfish are of great commercial importance. (Potamobius) which are used in the USSR as a food product and are a valuable export item, lobsters (But-marus), lobsters (Palinurus) shrimps (Crangon, Pandalus) as well as many crabs (Cancer, Callinectes). In the USSR, the crab-canning industry is highly developed, using the "Kamchatka crab" - Raga-lithodes catntschatica.

Suborder 1. Natantia combines the most primitive forms of decapods with a well-developed long abdomen, carrying limbs used for swimming. Typical representatives of this group are a variety of shrimps: pandalus(Fig. 229, L), Crangon and etc.

Rice. 299. Representatives of decapods. A - shrimp Pandalus borealis; B - crab Carcinus mae-nas; IN - Cancer hermit Pagurus bernltardiis(from Birstein)

Suborder 2. Reptantia. In terms of the number of representatives, it is much larger, includes forms that differ both in structure and biology. common feature is that they do not use their abdominal limbs for swimming. The latter are much less developed than in representatives of the subtr. Natantia are often rudimentary and reduced in number.

The Reptantia are subdivided into several "divisions". Typical representatives of the Palinura division are lobsters (Palinurus)- rather large marine crustaceans, without claws. The forms belonging to the department Astacura are also widely known - lobsters (Homarus) freshwater crayfish (Potamobius; see fig. 252); The department Anomura, or part-tailed, includes a variety of hermit crabs (for example, Pagurus; rice. 299.5), hiding their soft asymmetrical abdomen in empty gastropod shells. Some part-tails have moved on to life on land: the ground hermit crab- Coenol-1a, robber crab - Birgus latro. The latter is of great interest as a form more or less well adapted to the terrestrial way of life. The robber crab lives on some islands of the Pacific and Indian Oceans away from the sea, digs a shallow mink, which leaves only at night. It feeds on the oily fruits of tropical plants. During the hatching period of the larvae from the egg, the female leaves for the sea. The hatched larvae live in plankton for several months, and then sink to the bottom. Here they climb into empty shells of mollusks and become very similar to typical hermit crabs. In this form, they go to land, where after a while they leave a shell and turn into adult robber crabs.

belongs to the same department king crab - Paralithodes camlschatica(Fig. 300), outwardly similar to real crabs (p. 330). It never uses mollusk shells, but its small, forward-curving belly retains an asymmetrical build.

Representatives of the Brachyura department (short-tailed, or crabs) are distinguished by a small, symmetrical abdomen bent under the chest, short antennae and a wide carapace. This includes marine commercial crabs Carcinus(see Fig. 299,B), Cancer and many others, as well as some freshwater and even terrestrial forms.

Higher crustaceans (Malacostraca)

The higher crustaceans differ from the lower ones by a constant number of body segments equal to 15, and the first 8 segments - the thoracic ones - always differ sharply from the posterior 7 - abdominal ones. Usually they are much larger than the lower ones. Most of them live in the water, although there are some terrestrial forms. Within the Rostov region. there are representatives of five orders of higher crustaceans, namely: flmphipoda - amphipods, Cumacea - cumaceans, Mysidae - mysids, Isopoda - isopods, Decapoda - decapods.

Before proceeding to the description of individual orders, one should dwell on the features of the fauna of higher crustaceans of the Rostov region, due to the geological past of the river basin. Don.

The fact is that in freshwater and inland water bodies in general, higher crustaceans are usually very poorly represented - in contrast to the seas, where they are very numerous. IN fresh waters usually only one species of amphipods, isopods, and decapods is found, and the rest of the orders are completely absent. Meanwhile, in the reservoirs of the region, and especially in the Don, there are numerous representatives of amphipods, mysids and kumatsey of clearly marine origin. This interesting phenomenon is explained as follows.

At the end of the Tertiary period, on the site of the Caspian, Azov and Black Seas, there was one slightly saline sea - the so-called Sarmatian, which was not connected with the Mediterranean and had a peculiar fauna that differed from the fauna of other seas.

Later, the Sarmatian Sea was divided into two parts: eastern and western. From the eastern part, the modern Caspian Sea arose, which remained closed and preserved the ancient fauna of the Sarmatian Sea in an almost untouched form. From the western part formed the Azov and Black Sea. The Black Sea was connected by a strait with the Mediterranean. As a result of this connection, the Black and Azov Seas were filled with waters mediterranean sea, the level of which was higher. The highly saline Mediterranean waters, which had a different chemical composition, normal for all oceans in general, were inhabited by ordinary marine fauna, which penetrated in massive quantities into the Black and Azov Seas and populated them almost entirely. The ancient peculiar fauna of the Sarmatian Sea perished in a new environment for it and survived only in heavily desalinated estuaries and areas of the Black and Azov Seas adjacent to the mouths of the rivers, or was pushed back to the lower reaches of the rivers, having adapted to completely fresh waters. As a result, in the lower reaches of the Don, Dnieper and other rivers of the Azov-Black Sea basin, we find a large number of marine origin forms that differ sharply from the usual marine fauna (including the fauna of the open parts of the Azov and Black Seas) and coincide with modern fauna. Caspian Sea. These forms in the conditions of the Don and Sea of ​​Azov are considered Sarmatian "relics", i.e., the remains of the fauna of the ancient sea, and are essentially living fossils - witnesses of long-gone geological epochs. In addition to the above groups of higher crustaceans, some mollusks and worms also belong to the Sarmatian relics.

It is remarkable that most of the relict forms are concentrated almost exclusively in the Don, and in the Don delta they adhere to its main branches with a clearly expressed river regime (current). In stagnant and overgrown water bodies, in floodplain lakes and swamps, relics are rare (only 2-3 forms, while there are at least 45 in the river).

1. Amphipoda (Amphipoda). Amphipods are small crustaceans, which usually have an arched, laterally flattened body. The head bears small eyes and two pairs of antennae; the body is equipped with 13 pairs of legs, adapted to a variety of ways of movement: the first two chest ones are used for grasping and are equipped with claws, the next five are used for running, the three anterior abdominal ones are for swimming, the three posterior abdominal ones are for jumping (Fig. 8). Amphipods have the ability to swim quickly on their side (hence their name). They live at the bottom of water bodies and feed on various organic remains and corpses.

Most amphipods found in the Don belong to the gammaridae family (Qammaridae).

The largest of them is Dikerogammarus, reaching 2 cm length - one of the few relics found not only in the riverbed, but also in floodplain reservoirs. Not much inferior to him are Chaetogammarus and Pontogammarus, which are distinguished by antennae, very densely feathered hairs and inhabit mainly sandy rifts and clayey soils eroded on rapids. These three amphipods, being comparatively large and strong crustaceans, spread far upstream the Don and are found even in the Voronezh region.

In the Don Delta and especially in its shallow branches on silty soils, flmathillina is often found, also relatively large (up to 1.5 cm) amphipod, characterized by a reddish color and a peculiar crest on the back from a series of pointed outgrowths. The same comb, but double, has Gmelina Kusnetzowi, its covers are impregnated with lime.

In the Don, there are also other, smaller, forms of gammarids (a total of 12 were found).

In addition to gammarids, on sandy and clay soils, and especially among the fouling of stones, piers and bridges, amphipods of another group, related to corophyids, Corophium, live. They differ from gammarids in that their bodies are not laterally flattened, and the second pair of antennae is unusually developed and equipped with pincer-like appendages (Fig. 9). Corophium are relatively inactive and live in tubular houses. Four species of Corophium were found in the Don, of which C. curvispinum is the most common. This small (not even reaching 1 cm length) the crustacean penetrated not only into the upper reaches of the Don, but also into the rivers of other basins, apparently spreading recently with the development of navigation (it builds houses for itself on various solid objects, including ship hulls).

Despite the variety of forms, amphipods rarely develop in mass numbers in the Don. In the Don Delta, large concentrations of amphipods are observed only in areas with fast currents and dense soils (clay, shell), where their number reaches 1,700 specimens per 1 sq. m bottom (moreover, 1450 specimens of them belong to Corophium species).

It is remarkable that the well-known purely freshwater amphipod, widespread in general in fresh water bodies - Gammarus pulex - is completely absent in the Don; apparently, it has been supplanted by relict forms.

2. Kumacei (Cumacea). Kumacei are very small higher crustaceans, distinguished by the presence of a shell covering the front half of the chest, and a very thin abdomen, ending in two appendages in the form of a fork. On the chest there are 5 pairs of legs that serve for swimming and running, and the head end is equipped with one reddish eye. Kumacei live on the bottom, feeding on detritus (crushed organic residues) and give birth to live young.

In the Don, they are represented by 10 relict forms, concentrated mainly in the riverbed and in the main branches of the delta.

The largest representative of cumacea is Pterocuma Sowinskyi, reaching only 12 mm length. This is an extremely peculiar crustacean, equipped on the dorsal side with a crest consisting of several pointed outgrowths (Fig. 10). The armor is often impregnated with lime. Males have extremely long, thin antennae, which are absent in females, which in the spring bear several dozen cubs - developing in a special bag under the breast. Pterocuma is distributed on almost all soils, but especially prefers silty sands and is completely absent among thickets. On silty soils of the underwater (marine part) of the Pterocuma delta, more than 340 specimens are found. for 1 sq. m.

Schizorhynchus eudorelloides is even more common. This is a smaller form (no more than 6-8 mm) with a thin armor, devoid of a crest and having a deep notch in front. Schizorhynchus is found in the lower Don in absolutely all flowing water bodies, and as single specimens even enters floodplain lakes and swamps. In the main branches and bedrock of the Don, it often develops in huge numbers, especially preferring the sandy-silty bottom, where the average number of this crustacean exceeds 1,000 specimens, and even reaches 32,500 specimens in some deep pits in the Don delta. for 1 sq. m.

Kumacea Stenocuma is also very common - small (up to 5 mm) a form with a pointed front edge of the armor, which also prefers silty-sandy soils.

Due to their small size and benthic lifestyle, kumacei can easily be overlooked when exploring water bodies. Developing in mass quantities, however, they play a significant role in the nutrition of fish in the lower reaches of the Don.

The majority of Kumacei, apparently, lives only in the delta and in the lowest reaches of the Don. In any case, they are already completely absent in the Upper Don.

3. Mysids (Mysidae). Mysids are equipped with a thin transparent armor covering the chest, have an elongated, rather thick and strong abdomen, ending in lamellar fins. The head is numb with long antennae and large black eyes set on stalks. The body of the mysid is very gentle and transparent. They swim well with their 8 pairs of swimming legs and are able to produce fast jumps with the help of blows of the muscular abdomen. Like Kumacei, they breed live cubs, which they bear in a special bag. Most mysids avoid bright lighting and stay in the bottom layers during the day, and rise to the surface at night. Well-developed complex "faceted" eyes allow them to see well at night.

At least 8-9 species of mysids are found in the Don. The largest representative is Paramysis baeri reaching more than 3 cm length. It is a strong and fast moving crustacean resembling a miniature shrimp (Fig. 11). Metamysis Strauchi is very similar to it, differing only in slightly smaller sizes (up to 2.5 cm), reddish coloration and the structure of the "telson" - the middle caudal fin (in Metamysis, the telson has many teeth, in Paramysis - only 2).

Both mysids mentioned are usually found in small quantities. Incomparably more numerous than them is Mesomysis Kowalewskyi, similar to the two previous ones, but differing in the structure of the telson and smaller sizes (up to 1.5-2 cm). Mesomysis Kowalewskyi (as well as M. intermedia, which is closely related to it), inhabits the branches of the Don delta in large numbers, and especially the lower sections of the channels adjacent to the sea, and shallow bays of the seashore. Due to their rapid mobility, mysids easily elude the fishing gear used by hydrobiologists, and therefore the existing data on the number of mysids (up to 50-100 specimens per 1 sq. m) are understated. Dense-mesh drags and trawls, used by the Institute of Fisheries for catching juvenile fish, in the lower reaches of the delta often bring a continuous porridge from these crustaceans, among which only an insignificant admixture is made up of fish fry and other animals. Naturally, mysids are an important object of food for fish in the delta, especially since, due to the absence of a solid skeleton, they are a highly valuable food.

In addition to the listed forms, the Don also contains Diamysis and Limnomysis species. These are small (about 1 cm) mysids, characterized by long eye stalks. In contrast to the other mysids, Limnomysis lives mainly in thickets and is absent from the bedrock of the river; it is found in small quantities in floodplain water bodies.

Above the delta, and even in the upper parts of the delta branches, the number of mysids drops sharply. Only the most large forms- Paramysis and Metamysis - spread far up the Don and is found even near Voronezh.

In addition to water, there are also isopods that have adapted to a terrestrial lifestyle. This includes wood lice (Oniscidea), living in damp places, basements and houses. People unfamiliar with zoology usually refer them to centipedes or insects, while these are real crustaceans with all the signs of their order. In the Rostov region they are widespread, but not systematically studied at all.

5. Decapods (Decapoda). Decapods are the most highly organized and largest crustaceans, distinguished by the presence of 5 pairs of well-developed walking legs, of which the first, and sometimes the next few, are equipped with strong grasping claws. The cephalothorax of decapods is covered with a solid armor, often of considerable strength; at the anterior end are a pair of stalked eyes and long antennae. A thick and muscular abdomen (in some forms, however, reduced) is equipped with a caudal fin and swimming legs, on which eggs (caviar) are usually also laid.

In fresh waters and in particular in the reservoirs of the Rostov region. only one representative of decapods lives - crayfish. Although the sizes and colors of crayfish from different water bodies are very different, they all belong to the same species - the long-clawed crayfish (Rstacus leptodactylus). Within the Rostov region. long-toed crayfish is ubiquitous, but prefers weakly flowing water bodies, especially small tributaries of the Don and minor branches of the Don delta. It lives among thickets, sometimes in burrows, and feeds on a wide variety of objects, ranging from small fish to decaying plant debris and corpses. Apparently, the main part of his food is various underwater plants. At the end of autumn, mating of crayfish and fertilization of females takes place, which then, until May of the next year, bear eggs on their abdomen. At the end of May, juveniles emerge from the eggs. Cancer grows very slowly, and, like all arthropods, only during periods of molting, when the old chitinous cover is shed, and the new one has not yet hardened. In young crustaceans, molting occurs several times during the year, while adults molt once a year (in summer). The life expectancy of crayfish has not been precisely established, in any case, it is quite significant - at least 15 or even 20 years.

Crayfish in the Don basin is the subject of systematic fishing, carried out with special traps with bait ("crayfish") or bag-shaped fishing gear that is pulled along the bottom like a trawl ("saki" and "spreaders"). Crayfish are caught from May to October - November, and are carried out mainly at night, when the crayfish is most mobile (being a predominantly nocturnal animal, it hides during the day). The catch of crayfish in the lower reaches of the Don is several million pieces a year. The size of the annual catch of crayfish in 1938-39. make up about 2200 centners, or 4.4 million pieces (according to Lzdonrybtrest and Rostrybtrest). The commercial value of cancer is significant because it is not only consumed in local markets, but also exported in large quantities, and also goes for the preparation of canned food ("cancer neck" - more correctly, abdomen).

Higher crayfish (Malacostraca)- this is the class of the largest crustaceans, which include: crayfish, shrimps, crabs, wood lice and amphipods. This is the most large class by the number of crustaceans, where there are more than 35,000 species. They live in the seas, fresh waters and on land. They often hide under rocks or logs. Crustaceans are most active at night and feed mainly on snails, insect larvae, worms and amphibians; some eat vegetation. The female lays eggs in spring. Eggs attached to the female's abdomen mature in 5-8 weeks. The larvae remain with the mother for several weeks. Some top-class crayfish reach puberty in a few months, and some in a few years, and their life expectancy ranges from 1 to 20 years, depending on the species.

Structural features

Relatively large freshwater crayfish of the highest class have a smooth, shiny dark blue and green carapace. A feature of males is a bright red color on the edge of large claws. Males can reach a maximum weight of 500g and females 400g. Juveniles (less than 20-30g) can be sexed by the position of the gonopore adjacent to the fifth pereiopods (walking legs) for males and the third legs for females.

The higher crayfish class is characterized by a connected head and chest, or middle part, and a segmented body that is yellow, green, red or dark brown. The head has a pointed muzzle, and compound eyes are on movable stems. The exoskeleton is made of chitin, it is thin but tough. The front pair of five pairs of legs has large, powerful claws (chelae). There are five pairs of small appendages on the abdomen, used mainly for swimming and circulating water for breathing.

The body of a decapod crustacean such as a crab, lobster, or shrimp is composed of twenty body segments grouped into two main body parts: the cephalothorax and abdomen. Each department may have one pair of appendages, although in different groups they may be reduced or absent. On average, they grow up to 17.5 cm in length.

Most adult crayfish of the highest class are about 7.5 cm long. Among the smallest is the 2.5 cm pygmy blue crayfish (lat. Cambarellus diminutus) from the United States. Among the largest is Astacopsis gouldi from Tasmania, which can be up to 80 cm long and weigh up to 5 kg.

Habitat

The class higher crayfish are members of the superfamily Astacoidea and Parastacoidea. They breathe with gill-like feathers. Some species live in fresh water streams, while others thrive in swamps, ditches, and rice fields. Many species of the higher crayfish class do not tolerate polluted water, although some, such as crayfish California red (lat. Procambarus clarkii), is more durable. Crayfish feed on animals and plants, living or decaying, and detritus.

In Australia (for east coast), New Zealand and South Africa the term crayfish usually refers to the piercing lobster of the genus Jasus, which is found in most of southern Oceania,

while freshwater species crayfish are commonly referred to as "yabby" or "kura". The exception is Western lobster stones (family Palinuridae), found on the west coast of Australia; Tasmanian giant freshwater crayfish (of the Parastacidae family) found only in Tasmania; and Murray crayfish, found on the Murray River in Australia.

In Singapore, the term crayfish usually refers to Thenus orientalis, a marine crustacean in the talus lobster family. True crayfish are not native to Singapore but are commonly found as pets or as invasive species, For example Australian red claw crayfish (lat. Cherax quadricarinatus) found in many watersheds and is also known as freshwater lobster.

Families and species

The class of higher crayfish is divided into three families, two live in the Northern and one in the Southern Hemispheres. The Parastacidae family is distributed in the Southern Hemisphere (Gondwana), Madagascar and Australia. They are distinguished by the absence of the first pair of pleopods. Of the other two families, members of the Astacidae live in western Eurasia and western North America, while members of the family Cambaridae live in eastern Asia and eastern North America. Madagascar has an endemic genus, Astacoides, containing seven species.

The greatest diversity of species is found in the southeastern part North America, and over 330 species in nine genera, all from the family Cambaridae. Another genus of astacid crayfish has been found in the Pacific Northwest and in the headwaters of several rivers east of the continental gap. Many crayfish are also found in low-lying areas where the water is rich in calcium and oxygen rises from underground sources.

The upper class crayfish were deliberately introduced into several Arizona reservoirs and other water bodies many years ago, primarily as a food source for fish. They have since spread widely outside of this region.

There are more than 100 species of crayfish of the highest class in Australia. In this area, many of the known crayfish belong to the genus Cherax. Here are the views that are among the most major representatives crayfish in the world. They grow to several

kilograms. Many large Australian crayfish are endangered. Australia is home to two of the world's largest freshwater crayfish - the Tasmanian giant Astacopsis gouldi (pictured above), which can reach a mass of over 5 kilograms (found in the rivers of northern Tasmania) and Murray's crayfish (lat. Euastacus armatus), which can reach 2 kilograms and is found in most of the southern Murray-Darling basin.

fossils

Fossils that support the existence of a class of higher crayfish have been found in New Zealand over 30 million years ago, and fossil burrows have been found from layers as old as the late Paleozoic or early Mesozoic. The oldest records of them are in Australia and date back 115 million years.

Diseases of the higher cancer class

Unfortunately, higher cancers also suffer from diseases. Crayfish had a plague caused by the North American aquatic form of Aphanomyces astaci, which was transmitted to Europe when North American crayfish were introduced there. Species of the genus Astacus are particularly susceptible to infection, which has led to the spread of the disease throughout Europe.

Higher crayfish as food

Top class crayfish are eaten all over the world. In all edible crustaceans, only a small part of the body is eaten. In most cooked dishes such as soups, biscuits and
others, serve only the tail. But observant Jews do not use crayfish in their food.

As of 2005, Louisiana supplies 95% of the crayfish collected in the US. About 70% of these crayfish are Procambarus clarkii (red marsh crayfish) and the remaining 25% are Procambarus zonangulus (white river crayfish).

crayfish as bait

Crayfish are usually sold and used as bait to attract catfish, walleye, trout, salmon bass, salted bass, pike. The result of using crayfish as bait has sometimes led to various environmental issues. According to a report prepared State University In Illinois, on the Fox River and the Des Plaines River, a "rusty crayfish" (used as bait) was thrown into the water, and the survivors outwitted the indigenous transparent crayfish and settled the region. A similar situation has been repeated many times, as bait crayfish eliminate native species.

Crayfish are also used as bait to spread zebra mussels to various waterways, as members of this invasive species are known to attach themselves to crayfish.

Higher crayfish - pets

Higher crayfish species Procambarus clarki are pets. They eat foods such as shrimp balls, various vegetables, and also eat food from tropical fish, regular fish food, seaweed waffles and small fish that
can be grabbed with pincers. Sometimes crayfish eat their old carapace after molting. Since crayfish are accustomed to being in ponds or rivers, they tend to dislodge the gravel at the bottom of the tank, creating mounds and trenches to emulate a burrow. Crayfish will often try to get out of the tank, especially if there is a hole in the top that they can crawl through, as they are wild animals after all.

If you find an error, please highlight a piece of text and click Ctrl+Enter.