Class higher crayfish (malacostraca). Subclass v. higher crayfish (malacostraca)

Higher crayfish are characterized by a constant number of segments: the head consists of an acron and 4 segments, the chest - of 8 segments, the 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 Crustacea
  • Subclass Higher crayfish

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 (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

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.

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,

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 divide. 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

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. There was a plague in crayfish 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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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 salt waters, as well as on 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 live only in the aquatic environment, salty or fresh, they 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. This brings great harm to ships, 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 way of 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 by the scientific community, the entire systematization will have to be reworked: new common features should be identified and the grouping into a taxon based on the degree of relatedness of species should be abandoned.

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, bright green colored claws. They have a powerful impact force, 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.

In most cases, cancers are of medium or large size. The body consists of 20-21 segments: 5-6 head, 8 thoracic and 7 abdominal. At many the tendency to merge of segments with formation of a cephalothorax is observed. The limbs are located not only on the head and chest, but also on the abdomen. The excretory ducts usually open at the base of the antennae. Development occurs either without transformation, or with the stage of a kind of larva - zoea, which, unlike the nauplius of lower crayfish, has a dissected body (Fig. 130). Higher crayfish inhabit the seas, lakes, ponds and rivers, but some of them (woodlice) have adapted to life on land.

From the orders of this subclass, we will consider the isopods and decapods, which are of the greatest importance for the commercial and agriculture of our country.

Squad isopods(isopoda) - small crustaceans with a flattened body (Fig. 131). The head is fused with the anterior thoracic segment, the rest of the thoracic segments are free. Each segment of the thorax and abdomen bears a pair of relatively short legs. The group includes various types woodlice, living on land (usually in wet places), water donkeys, living in large numbers in lakes and ponds, and many marine forms.

Woodlice in places cause significant damage to cultivated plants, especially in greenhouses and greenhouses.

Squad Decapods (Decapoda)
- the most highly organized crustaceans of medium or large size (Fig. 132). The head and all segments of the thorax are fused into a cephalothorax, covered from above and from the sides by a cephalothoracic shield, the chitin of which is usually impregnated with lime. There are eight pairs of thoracic limbs, of which three forelimbs - the jaws - are involved in obtaining food, and the remaining five pairs serve to move the animal (walking legs). In many species, the front pair of walking legs bear powerful pincers. The abdomen has six pairs of legs. Decapods are divided into three groups: long-tailed, soft-tailed and short-tailed.

Longtail crayfish- crayfish and sea crayfish - lobsters and lobsters, shrimps, etc. They have a well-developed abdomen, which carries a caudal fin at the end, formed by the last segment of the body and wide lobes of the legs of the penultimate segment.

Rice. 132. Decapods:

1 - shrimp; // - Cancer hermit; /// - crab

Crayfish settle in rivers with a quiet current, in ponds and lakes. During the day, they hide in burrows or under snags, and at night they come out in search of food. They feed on small benthic animals and carrion. Females hatch eggs by attaching them to the legs of the abdomen. Many long-tailed crayfish are of great commercial importance.

soft-tailed crayfish include hermit crabs living in the seas. Their abdomen is of medium size, curved, soft, without a terminal fin. This structure is due to the fact that hermit crabs live in spirally curved gastropod shells, in which they hide their abdomen. They have no economic value.

short-tailed crayfish(crabs) have a wide flattened cephalothorax, under which the abdomen is tucked. Many species are used as a food product.