Higher crayfish (Malacostraca)- this is the class of the largest crustaceans, which include: crayfish, shrimps, crabs, wood lice and amphipods. This is the largest class in terms of abundance 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

Crayfish

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 separated by sex 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 thorax, or middle part, and a segmented body that is yellow, green, red, or dark brown in color. 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.

Lobster

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 they may be reduced or absent in different groups. 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 (on the 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,

Tasmanian giant freshwater crayfish

while freshwater 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 such as 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 southeastern North America, with 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 species that are among the largest representatives of crayfish in the world. They grow to several

Murray cancer

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 problems. On the Fox River and Des Plaines River, a "rusty crayfish" (used as bait) was dropped into the water, and the survivors outmaneuvered the indigenous transparent crayfish and settled in the region, according to a report prepared by Illinois State University. 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, as well as tropical fish food, common 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.

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SUBCLASS V. MALACOSTRACA

number of segments: 4 cephalic, 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

11*

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 shrimps (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 of the 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 the favorite food of 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.

Euphausia breed in masses in some areas of the sea, where they serve as food for various marine mammals and fish. So, 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 shrimps is 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. BUT - shrimp Pandalus borealis; B - crab Carcinus mae-nas; AT - 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. A 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 far from the sea, digs a shallow mink, which it 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.

The king crab belongs to the same department - 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.

SUBCLASS HIGHER CRABIES (MALACOSTRACA). This class includes crustaceans of medium and large sizes, inhabiting marine and fresh water bodies; some have adapted to life on land. Their body is characterized by a constant segmental composition and consists of an acron and four head segments, eight thoracic and six to seven abdominal segments. Often the head and thoracic segments fuse to form the cephalothorax. There are limbs on all segments, including the abdominal ones. Development occurs without transformation or with the zoea stage. In lower crayfish, development occurs with the nauplius stage. The zoea larva, unlike the nauplius, has an elongated and dissected body. The growth of crayfish is accompanied by molting

Order Isopods (Isopoda). There are 4.5 thousand species of small crayfish with a flattened body in the detachment. The anterior thoracic segment merges with the head section. Faceted eyes. There is no carapace. The segments of the thorax and abdomen each bear a pair of short legs. Walking pectoral legs are single-branched and of the same structure, which determined their name "isopods". The ventral legs are biramous and perform a respiratory function. The order of isopods includes water donkeys, which abundantly inhabit sea and fresh water bodies. Among the isopods there are forms that have adapted to life on land.

Order Amphipoda crayfish. Representatives of amphipods, or amphipods, number about 4.5 thousand species. Especially a lot of them live in the seas, less often found in fresh waters. On land, heteropods were not found. Their structure is similar to the structure of isopods: on the head are sessile compound eyes, a segmented thoracic region without a carapace, and single-branched thoracic legs. However, amphipods also have differences: the body is flattened from the sides, the pectoral legs differ in structure - "diverse". The first two pairs of legs perform grasping functions and are armed with claws. The remaining five pairs of pectoral legs are used for crawling and swimming. The thoracic legs have a gill apparatus at the base, so the heart of amphipods is located in the chest, while in isopods it lies in the abdominal region.

Order Decapod crayfish (Decapoda). These include the largest and highly organized crustaceans that inhabit mainly the seas and less often fresh waters, there are land forms. There are 8.5 thousand species in which the segments of the head and chest are fused into the cephalothorax, covered from the sides and top by a cephalothoracic chitinous shield - a carapace. The chitin of the shield is impregnated with lime. Of the eight pairs of thoracic limbs, three forelimbs are involved in the capture of food; these are the so-called jaws. The remaining five pairs are walking legs; with their help, crayfish move. Often the front pair of walking legs ends in powerful claws. The abdomen is represented by six segments, each of which bears a pair of legs. The gills are located not only on all the pectoral legs, but also on the body at the base of the legs. The carapace covers the body from the sides, forming gill covers. The abdomen has a caudal fin formed by the last segment of the body and wide lobes of the legs of the penultimate segment. In some decapods, the abdomen is reduced. Development is direct or with metamorphosis. Representatives of this suborder have a pronounced tendency to move by crawling, while the ability to swim is significantly reduced. Lobsters and lobsters have a muscular and long abdomen, they can swim. In hermits, the abdomen is asymmetrical and underdeveloped; crayfish hide it in empty shells of mollusks or bend it under themselves. In crabs, the abdomen is reduced. Crayfish live in fresh water bodies with a slow current and clean water. They lead a nocturnal and twilight lifestyle, feeding on benthic animals and carrion. Females carry fertilized eggs by attaching them to the legs of the abdomen.

Taxonomy: Type Arthropoda (Arthropoda) - Class Crustacea (Crustacea) - subclass Higher crayfish - order Equinopods, Diplopods, Decapods.

Representatives: Pandalus borealis shrimp, Pagurus bernhardus hermit crab, Carcinus maenas crab

Higher crayfish are characterized by a constant number of segments: the head consists of an acron and 4 segments, a chest of 8 segments, and an abdomen of 6-7 segments and a telson. Unlike other subclasses, higher crayfish have ventral limbs and the telson does not have a furca. The male genital opening always opens on the eighth thoracic segment, the female genital opening on the sixth. In larvae, maxillary kidneys function, in adults - antennal, only Nebalia have kidneys of both types in the adult state. Development in some species is direct, in others - with transformation. A typical larva is a zoea.

The subclass Higher crayfish is subdivided into orders: 1) Isopods (Isopoda), 2) Amphipods (Amphipoda), 3) Decapods (Decapoda), etc.

rice. one. Woodlouse
(Porcelio sp.)

Order Equinopods (Isopoda)

The isopods have a body flattened in the dorsal-abdominal direction. The carapace is missing. On the head are sessile compound eyes. The thoracic region consists of 6-7 segments. The pectoral legs are single-branched, walking, having the same structure (hence the name of the detachment). The ventral legs are biramous, leaf-shaped, and perform a respiratory function.

Woodlice- crustaceans adapted to the terrestrial image (Fig. 1). Herbivorous. Some species of woodlice retain gill breathing, these species live in places with high humidity, and they have adaptations for constantly moistening the gills. In other species, the anterior abdominal legs carry the organs of air respiration - pseudotracheae, similar to insect tracheas. The pseudotrachea begins with respiratory openings that lead to deep and branched protrusions of the integument. Through the walls of these invaginations, oxygen penetrates into the hemolymph.

Females incubate eggs in a brood chamber on the thoracic region from below. In our region, species of the genera Porcelio and Oniscus are more common than others.

Species of woodlice living in the desert dig deep holes.

Order Diverse, or amphipods (Amphipoda)

rice. 2.

Diverse crustaceans have a laterally flattened body. The carapace is missing. On the head are sessile compound eyes. There are seven pairs of thoracic legs, they are single-branched, carry gills and have a different structure (hence the name of the detachment). The first two pairs are grasping, ending in claws that serve to capture food. The next two pairs end with claws pointing backwards. The last three pairs are longer than the rest of the limbs and are directed forward with claws.

Limbs with claws are used for swimming and crawling. The abdomen consists of six segments and a telson. The first three pairs of ventral legs are biramous and multisegmented, used for swimming. The next three pairs are directed back and serve for jumping. Reproduction is sexual. Development without transformation. Females incubate eggs in a brood chamber located on the thoracic region from below.

Most species of amphipods lead a benthic lifestyle, feeding on organic remains. Some species are planktonic.

Description of other classes and subclasses of the phylum Arthropoda:

• Class Crustaceans
  • Subclass Higher crayfish

blue cuban crayfish

Crustaceans live in aquatic or humid environments and are close relatives of insects, spiders, and other arthropods (type Arthropoda). The peculiarity of their evolutionary series is to reduce the number of metameric (identical) segments through their merging with each other and the formation of more complex body fragments. According to this feature and other characteristics, two groups are distinguished: lower and higher crustaceans. So, let's get to know these animals closer.

Lower and higher crustaceans: characteristic differences

The lower crustaceans differ in small, up to microscopic sizes. In addition, they do not have abdominal limbs, but only chest ones. Unlike primitive forms, higher crustaceans are characterized by a constant (6 pieces) number of identical body segments. For simply arranged crustaceans, the number of such formations ranges from 10 to 46. Moreover, their limbs, as a rule, are biramous. While, in some highly developed animals, this feature disappears. So, in crayfish, the thoracic limbs have one branch.

cherry shrimp

Shrimp Lysmata amboinensis and giant moray

The lower crustaceans are characterized by a softer chitinous cover. Some of them (daphnia, in particular) have transparent shells through which the internal structure is visible. The respiratory system in higher crustaceans is represented by gills. More primitive forms breathe the entire surface of their body, while the bloodstream in some may be completely lost. The nervous system of highly developed species with a variety of behavioral reactions has a complicated structure.

Daphnia (lat. Daphnia) - a genus of planktonic crustaceans

These animals are characterized by well-developed external formations that perform the function of balance (statocysts); bristles covering the entire body, increasing sensitivity; organs that capture the chemical components of the environment. Some lower crustaceans do not have a peripharyngeal ring, their brain is more primitive, while in more developed organisms ganglia merge, their structure becomes more complex.

Lobster, he is a lobster (lat. Nephropidae)

Diversity of biological forms of lower and higher crustaceans

Shrimp "Red Crystal"

Higher species of crustaceans, in particular crayfish, crab, lobster, spiny lobster, and shrimp, play a special commercial role for humans. A useful product consisting of planktonic crustaceans Bentheuphausia amblyops, is krill meat. Has the same lifestyle Macrohectopus branickii living in Lake Baikal. Land woodlice living in moist soil are also highly developed representatives.

Cambarellus patzcuarensis is an endemic type of crayfish

Amphipod Parvexa, an endemic crustacean that lives in about. Baikal

Cancer - mantis (lat. Odontodactylus scyllarus), also known as shrimp - mantis

And in more detail with the various species belonging to this class, with lower and higher crustaceans, you will be introduced to the new articles of the online magazine "Underwater World and All Its Secrets":