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Animals such as molluscs. Classes of mollusks and their characteristic features

I often get confused about the names of shell seafood (or scientifically bivalves and gastropods). So I put together a small selection interesting information, pictures and descriptions of the most popular (delicious) subspecies.

These mollusks live in both salty and fresh water, lead a sedentary lifestyle, attached to solid objects or... to their relatives. This is exactly how fishermen caught them in ancient times: a wooden pole was lowered into the water and after a little over a year, its lower part was all “hung” with mussels. With the help of a leg or shell, some species are able to move quickly. Mollusks mainly feed on unicellular algae, tiny plankton and other organic particles contained in the water. Sea water through the slightly open valves it reaches the gills and passes through the mollusks, as if through a filter. Food is transported into the body and mineral particles are removed. Thus, mollusks are active water filters: one individual pumps up to 3 liters of water per hour through itself. They prefer to live in running water because they use sea currents shellfish can feed without special effort- passing through the gills required amount water. Due to these characteristics of the body, they live only in fairly clean water.

The shell of mollusks has two valves, which are controlled by opening muscles and, if necessary, are able to fit tightly against each other. This makes it possible for a soft-bodied animal to reliably isolate itself from environment. The inner surface of the shells is lined with a layer of mother-of-pearl, and the body of the mollusk is covered with a fleshy film - the mantle. Often there may be grains of sand in the sink: you should wash them well with running water, or even better, soak them in salt water for an hour or two before cooking (or wait until the grains of sand turn into pearls)! Some types of shellfish are eaten raw, while others are stewed, fried or boiled. Do not forget, it is very important to eat only fresh shellfish: the shells of mussels and bettas must either be tightly closed (except for scallops, which are sold with open shells) or closed from touch (for oysters). I recommend not eating those shells that did not open during heat treatment.

Mussels / mussels / cozze.

Mussels differ in size (from 5 to 20 cm), shell color (from blue-black to golden brown), life expectancy (from 5 to 30 years) and the taste of the meat. It is believed that warm-water mussels have more tender and softer meat, while those found in cold water- rougher. In terms of protein content, mussel meat is superior to beef and fish. The highest taste qualities possess mussels caught from June to February.

All the insides of the shell are edible (except for the leg), they are very tasty stewed in white sauce (from butter, parsley, garlic and white wine) or in red sauce (from tomatoes, the same garlic and white wine, finely sautéed shallots, oregano , thyme and hot red pepper).

There is a special subspecies of mussels bearded horse mussel / cozza pelosa, the Russian name for which I did not find. Italians especially love and appreciate them.

On the coast Mediterranean Sea there is a French village called Bouzing. It is considered the capital of mussels - there they can be found in any cafe, where they are cooked along with grilled sausages and served with local wines. However, glorious traditions of eating mussels exist not only in France. For example, in Odessa, this product was sometimes prepared right on the beach - on a sheet of iron fixed over a fire.

Just like the scallop, the muscle and mantle of the mussel are eaten. This mollusk passes a huge amount of water through its body, acting as a kind of filter. Therefore, they are prepared like this: they wash and sort out the shells, and keep them in cold water for several hours. Then I wash it again and cook in salted water for 15-20 minutes. After this, the shells should be opened and the meat should be removed from them, rinsing again in boiled water. After this, you can prepare salads, cold and hot appetizers, and soups from mussels.

Of course, mussels are very healthy. Their meat contains more than 30 useful microelements, as well as B vitamins: B1, B2, B6, vitamin D and PP.

Oysters / oysters / ostriche.

Because of their tasty and healthy meat, oysters have been eaten for many hundreds of years. It was always believed that oyster stocks were inexhaustible, but as a result of uncontrolled fishing in the mid-nineteenth century, the question arose about the need to regulate their collection and introduce artificial breeding. There is a legend that the oyster season lasts only in those months that have the letter “r” in their names (i.e. from September to April) due to the fact that, firstly, summer months wild oysters multiply and secondly due to the difficulties of storing and transporting them in the warm season. However, now 95% of the oysters consumed are grown on farms, well modern methods Their cultivation allows them to be consumed all year round. I would never have thought that the United States is the world's largest producer of oysters; Americans eat as many as 2.5 billion oysters a year. The oyster growing period lasts from three to four years, during which time the mollusk grows from 5 to 15 centimeters in size; although individuals of some species reach as much as 45 centimeters.

In nature, there are 2 genera of oysters: European (Ostrea or flat) and Pacific (Crassostrea or deep). European oysters are usually named after the area where they were grown: belons, gravettes, olerons, etc. Pacific - according to cultivation technology: fine de claire, speciales de claire. Those oysters that live in cooler waters are tastier, and their meat is more tender and juicy. For flat oysters, size is indicated by zeros, the largest being four zeros. For deep oysters, the size is indicated by numbers, the most big size- first. Traditionally, oysters are sold by the dozen.

Oysters are usually eaten fresh, with a little pepper and sprinkled with lemon juice. It is better to order medium-sized oysters (they are more tender), and oysters that are too large do not always fit in your mouth :). There is a popular belief that a fresh oyster squeaks. So, if you are holding a fresh oyster in your hands and hear a squeak, then stop squeaking :). An oyster lunch is well complemented by toasted rye bread with butter and wine vinegar sauce. The traditional method of consumption is as follows: the shell is taken into left hand, the body of the mollusk is separated from the muscle located in the middle of the shell, a little pepper and a couple of drops are added lemon juice and drink the oyster from the recessed side of the valve. But they don’t swallow it right away, but enjoy its juice, lightly chewing the meat. well and the best place in the world (IMHO) for eating this delicacy - the beaches of the French town of Cancale, where you can choose a couple of dozen of the freshest oysters at a small seafood market on the embankment. The seller will open them for you right away. And you can eat them by dangling your legs over the side of the embankment towards the ocean, carelessly throwing the flaps into the coastal sand (this is the custom!). In the same town you can visit the oyster museum and a farm that grows the most delicious, in my opinion, oysters on earth!

Scallops / scallops / capesante.

Scallops live in all the world's oceans and in many seas (even in the Black Sea they are found!). The bivalve shell of a mollusk is a symbol of the feminine water principle, which gives rise to all living things - it is the scallop shell that is depicted in Sandro Botticelli’s painting “The Birth of Venus”. The shell has a diameter of 15-20 cm, inside which is one of the main sea delicacies - scallop meat.

Scallop meat is tender and slightly sweet in taste. They can be eaten raw or used for cooking from salads to main courses. They are especially popular in French cuisine (my favorite dish Saint-Jacques - baked scallop in mushroom-cheese-cream-wine sauce with bread crumbs). Scallop fillet contains almost no fat and carbohydrates, but has a beneficial effect on male potency. Today, the scallop ranks third in quantity in the world production of shells, after oysters and mussels.

When you buy fresh scallops, inside the shell you will find creamy meat and sometimes a bright orange pouch of roe. Caviar has a slightly different consistency than scallop meat, but is no less tasty - cook it along with the meat. All other membranes and dark veins must be removed and not eaten. Scallop meat can also be sold frozen, but you need to be careful when buying it - scallops absorb water very well, which is often used by its sellers. Meat saturated with water becomes heavier - so weigh the scallop in your hand before buying; it should weigh less than an ice cube of the same size.

Scallops do not like long cooking - the simpler and faster it is cooked, the better. Fry it for 1-2 minutes on each side in a very hot frying pan lightly sprinkled with olive oil, and the scallop is ready. It is very convenient and beautiful to serve in its own shell.

This is the most common looking bivalve shell. Inside is a mollusk, the edible parts of which are the muscle and mantle. Moreover, people have been eating this mollusk since time immemorial - it was appreciated by residents of coastal areas Far East, long before Europeans first mentioned this product in literature in 1704. Boil the scallop in salted water for about 7-10 minutes. After cooking, the product is cooled and cut. It can also be baked or fried. Scallop Suitable for preparing gourmet appetizers and first course salads.

Scallop meat contains complete proteins and active lipids. This seafood is a valuable source of minerals such as sodium, calcium, magnesium, phosphorus, iron, copper, manganese, zinc, iodine and others. It also contains vitamins B1, B2, B6, B12. Scallops, like other seafood, are classified as “absolute taste” products that do not require spices or seasonings.

Sea cockerels (or simply mollusks) / clams / vongole.

The cockerels gave me the most trouble; the devil himself would break his head in the types and subspecies of these shells (there is not even an exact scientific definition of clams)! However, there are two main groups: soft-shelled and hard-shelled/fasolari, although soft does not mean that the shell is actually soft - it is simply thinner and more brittle than that of a hard clam.

Hard-shelled clams have shiny shells and meat-like long tongue with a bright orange tip, it is from them that it is prepared delicious soup Manhattan clam chowder, which I would recommend you try at the oyster bar at New York's Grand Central Station. Usually shells have a round shape (with the exception of sea shells / razor clams / cannolicchio, which are rectangular-oblong and date shells / dattero di mare - round-oblong, but catching and eating the latter is prohibited) - see. illustrations above.

Soft-shelled clams come with longitudinal and transverse ribbing. And their most popular subspecies are amande, venus, and palourdes, which are considered the best - see. illustrations above.

When choosing shellfish, use general rules- they must be very fresh, although they are rarely eaten alive. My favorite rooster dish is linguine alle vongole, which is also my favorite long Italian pasta.

Cardium/cockles

These shells are a little smaller in size and have a more rounded shell than cockerels; are used in exactly the same way as their older brothers.

Periwinkle (left) / winkles / buccini di mare and trumpeter (right) / whelks / chiocciole di mare.

Periwinkle and whelk are coastal sea snails. The soft body of the mollusk is hidden in a beautiful spiral-twisted calcareous shell up to 20 cm long and closed with a “curtain”. Their delicious orange meat is ideally absorbed by the body and is a source of complete proteins and microelements - especially iodine and fluorine.

Small shellfish are prepared directly in their shells - left overnight in fresh water, and then boiled for 5-10 minutes in prepared salty broth with spices and herbs. Sometimes, after cooking, the snails are dipped in a vinegar solution. Snails are served hot or cold, often with lemon, olive oil and vinegar, and the meat is eaten with small needles, carefully removed from the shells. The meat is very juicy, a little rubbery, with a strong taste. The most delicious snails I ate were at the restaurant Astoux et Brun in Cannes, near the Palais des Festivals and the Sunday fish market, they are served to all visitors as an appetizer. And you can stop gnawing on them only when the main dishes are brought out.

Now about cephalopods. Cephalopods, don’t take this as an awkward pun, are eight-legged and ten-legged. The first are octopuses, decapods are squids and cuttlefish. Of all this glorious company, squid is the most accessible and popular. Let's start with them.

Squid

There are about 300 species of squid, which live mainly in tropical waters. The sizes of squid can be very different: from 2-5 cm and a weight of 300 grams for an ordinary squid, to 18 meters in length and a weight of a couple of tons for a giant squid (octopus). Unfortunately, such squid cannot be eaten.

All squids have a conical body called a mantle with diamond-shaped fins and 10 tentacles around the mouth opening. The mantle has an ink sac; the black liquid that is in it serves the squid for self-defense.

They eat the muscular mantle and tentacles of squid, which are a protein product: 80% of the dry matter in them is protein. Squid meat is also rich in vitamins and minerals. Squid suckers, dried in a frying pan, are considered a special delicacy.

Cutting a squid carcass is quite simple: the ligaments between the head and body are removed, after which the head is separated along with the entrails. The remaining whole hollow carcass can be stuffed; the eyes and jaws are removed from the head.

Stores usually sell squid fillets. In any case, before cooking, you need to remove the thin skin covering the meat. To do this, the squid is kept in a hot water, after which the skin is easily removed. Cook the cleaned meat for 2-3 minutes.

Squid dishes are common in Mediterranean cuisine: it is stuffed or deep-fried, cut into rings, and used in salads.

Octopuses

Hundreds of species of octopuses are known, and all of them have a body consisting of a sac-like body and big head, on the front of which there are eight tentacles with suckers in two rows. Among the variety of species there are giant octopus(Paractopus dofleini), the body length of which reaches 60 cm, and the total length up to 3 meters. However, octopuses of more modest dimensions are eaten: the so-called “muscardini” weighing 40-100g. and larger specimens of 2-4 kg. Muscardini is cheaper and the cost increases in proportion to the weight.

Cephalopods are usually supplied to Russia by Spain, France, and Holland. But we also have our own fisheries: in the Far Eastern seas there are up to 14 species of octopuses weighing from 400 g to 12 kg. Octopus, like other seafood, is healthy; its meat has a high nutritional value than squid. Quality product not wrinkled and elastic when pressed.

Octopus is used in cooking both boiled and raw, sometimes the skin is also used. However, the most common option is boiled octopus.

Octopus is a popular dish on the Mediterranean coast. It is marinated, baked in breadcrumbs, and served fried with a vinegar and butter sauce.

Cuttlefish

The cuttlefish has a more flattened body than squids, surrounded by an oval mantle with narrow fins on the sides, four pairs of limbs and one pair of tentacles with suckers. Cuttlefish, which is less common on store shelves and on restaurant menus, is often prepared using the same recipes as squid or octopus. In the Mediterranean, the boiled product, served as a salad in a spicy marinade of olive oil. Small cuttlefish, prized for their subtle nutty flavor, are often deep-fried. There are two sizes of cuttlefish most in demand in cooking. Small (from 20 g) - for preparing appetizers, salads, kebabs. And larger ones - weighing 300-600 g, used in main dishes. A larger product is rarely used: the meat of a large cuttlefish is considered coarser. In general, cuttlefish are an interesting and unusual creature: they are capable of changing the color and structure of their skin in a matter of seconds. Their ink is still used to make paint that has a pure Brown color– sepia (from sepia – the scientific name of cuttlefish). By the way, cuttlefish ink is also used in cooking: most often for preparing Italian dishes - pasta, risotto, as well as some sauces.

Sea snails

There are several varieties sold in Philippine markets. It is difficult for a European to understand the subtle differences between them. Sometimes sellers specially cut off the ends of the shells to make it easier to pull the snails out. If you bought already crushed shells, then know that you need to cook them as soon as possible.

If you decide to buy whole shells, don't worry, I'll tell you how to get the edible part yourself. You just need to cook them, and then the snail body can be easily removed with a fork.

How to choose snails? Choose by smell. There is no smell, which means the shellfish are fresh and you can buy them. Sometimes they can be seen moving their legs in their shells.

How to cook snails? Can be boiled in coconut milk with garlic, onion and spices. All cooking takes no more than 5-7 minutes.

Tamilok - sea worm

And finally, the most exotic Filipino creature is the Tamil. The Filipinos themselves admit that they eat it occasionally. This is more of a tourist activity, for which locals travel to remote areas and collect worms. Tamilok is found in the trunks of rotting mangrove trees. Getting it is a real feat. You need to wander for a long time through fetid thickets in knee-deep or waist-deep water, looking for slimy and long mollusks. In Tamil markets it is sold in this form - in a special marinade that protects the worm from spoilage. Ingredients of the marinade: sugar, salt, vinegar and pepper.

After surfing the Internet, I was surprised to learn that Tamilok is not a worm, but a mollusk. Some compare its taste to oysters. Local residents eat it with alcohol.

As for me, Tamil is not intended for the European stomach. Taste of mud, slimy consistency, taste of vinegar... nothing special.

Guidak

Geoduck is a large edible gastropod weighing up to 1.5 kg of the Panopea generosa species, which is found off the west coast of the United States. Thin fragile shell This mollusk, up to 20 cm long, cannot completely cover the even longer protruding “neck” (neck), which we usually call a “leg” - this “leg” is three times larger than the shell.

The English name for this mollusk (geoduck, gweduck) appeared in late XIX century, is derived from the name of these mollusks in the language of the Nisqual Indians (which is why it is pronounced “guidak”) and means “deep-digging” - these mollusks really bury themselves quite deeply in the sand. The clam meat is quite tough and tastes like... abalone, so Americans usually cut it into pieces, beat it and fry it in butter with onions.

However, the bulk of the catch is exported to Japan (where the guidaka is called “murugai”), Taiwan and Hong Kong, where they are often eaten raw (for example, in Japan they are scalded, the skin is pulled off, the entrails are removed, they are thinly cut and made into sashimi).

Molluscs are soft-bodied, invertebrate animals. You can also hear such a concept as Molluscum contagiosum, which relates to medical topics.

Shellfish

Mollusks are invertebrate animals that live in sea and fresh water, as well as on land, where they are found even high in the mountains - approximately to the line of eternal snow.

The word molluscs translated from Latin (molluscus, mollis) means soft. Accordingly, the body of the mollusk is soft and undivided, most often protected by a shell. These animals are bilaterally symmetrical, but very often there are individuals in which asymmetry occurs due to secondary displacement of organs. Molluscs originate in the process historical development worms, we can say that they are relatives.

Seven classes of mollusks can be distinguished, which differ from each other in terms of appearance, and by way of life - these are gastropods, cephalopods, monoplacophorans, groove-bellied, bivalves, shovel-footed and armored.

Disease

Molluscum contagiosum, translated from New Latin - molluscum contagiosum - is a viral infection that is transmitted through direct contact with an infected person or through objects that he used.

Most often, the infection affects the mucous membranes of the external genitalia, the skin on the thighs and buttocks. Molluscum contagiosum consists of vesicles ranging in size from 1 mm to 1 cm in diameter, which protrude slightly above the surface of the skin. The color may not differ from the skin tone or be slightly pinkish; there is a yellowish nodule in the middle.

Animals with spiral crushing. Traditionally they are classified as protostomes. Today, the phylum Mollusca includes more than 150,000 species. Mollusks have mastered almost all habitats: marine and freshwater bodies, and land. These are mainly free-living organisms, but they also contain a number of parasitic forms. Shellfish include octopuses, squids, aquatic and land snails, and many others. Mollusks are studied by the science of malacology, and their shells are studied by conchology.

Dimensions

Dietary types: filter feeders, herbivores and carnivores.

Classification

Modern representatives of the phylum Mollusca form eight well-separated monophyletic classes. However, many fossil groups of mollusks are controversial both in terms of their taxonomic position and rank.

Classes of modern mollusks:

Caudofoveates or pit-tailed, Caudofoveata or Chaetodermomorpha.
Solenogaster, Solenogastres or Neomeniomorpha.
Armored or tunics, Loricata or Polyplacophora.
Tryblidia or Monoplacophora sensu stricto; were previously assigned to the class Monoplacophora, which turned out to be polyphyletic.
Bivalve, Bivalvia.
Spadefoot or boatopods, Scaphopoda.
Gastropods, or snails, or gastropods, Gastropoda.
Cephalopods, Cephalopoda: octopuses, squids, cuttlefish.

Extinct groups of mollusks of class rank:

†Multiplacophora had a shell of seventeen plates; perhaps relatives of the armored ones.
†Helcionelloida were formerly classified in the class Monoplacophora (Tergomia), a paraphyletic taxon.
†Stenothecoida were formerly classified in the class Monoplacophora.
†Rostroconchia are considered related to Bivalvia.
†Paragastropoda are not related to gastropods.
†Hyolitha is similar in shell structure to molluscs, but may not be a phylum.

In addition, there are a number of species of fossil mollusks, the systematic position of which within the phylum is still a mystery (for example, Halkieria, Wiwaxia).

Origin

Phylogenetic relationships between modern classes mollusks (after Salvini-Plawen and Steiner 1996, somewhat simplified).

The problem of the origin of the type of mollusks is debatable. Some biologists derived the hypothetical ancestor of mollusks from annelids, others from flatworms. Currently, the most widespread hypothesis is the origin of mollusks from primary coelomic trochophore animals, from which annelids also originate. About the relationship of mollusks and annelids some say common features organizations. Thus, a number of lower mollusks have retained the features of metamerism and have a scalene nervous system. In the embryogenesis of mollusks, features of similarity with annelids, inherited from common ancestors(spiral fragmentation, metamerism of some rudiments, etc.).

Sources

Dogel V. A., “Zoology of Invertebrates”, 7th ed., M., “ graduate School", 1981.
Biological encyclopedic Dictionary edited by M. S. Gilyarov et al., M., ed. Soviet Encyclopedia, 1989.
Zhadin V.I. 1952. Mollusks of fresh and brackish waters of the USSR.(Key guides to the fauna of the USSR, ed. Zool. Institute of the USSR Academy of Sciences. Issue 46). M.; L.: Publishing house of the USSR Academy of Sciences. 376 pp.
Scarlato O.A. Bivalves temperate waters of the northwestern Pacific Ocean.– L.: Nauka, 1981. – 480 p. – (Key guides to the fauna of the USSR, ed. Zool. Institute of the USSR Academy of Sciences; No. 126).

Salvini-Plawen L.V. & G. Steiner, 1996. Synapomorphies and symplesiomorphies in higher classification of Mollusca. Origin and evolutionary radiation of Mollusca (J. Taylor ed., Oxford Univ. Press): 29-51.

Mollusks are widespread secondary cavities, invertebrate animals. Their body is soft, undivided; in most it is divided into a head, torso and leg. The main characteristics of mollusks are the presence in most species limestone sink And mantle- skin fold covering internal organs. The oral cavity of mollusks is filled with parenchyma. The circulatory system is not closed. Over 130,000 modern species and approximately the same number of fossil species are known. Mollusks are divided into classes: gastropods, bivalve, cephalopods.

Class Gastropods

Class Gastropods- this is the only class whose representatives have mastered not only water bodies, but also land, therefore, in terms of the number of species of mollusks, this is the most numerous class. Its representatives are relatively small in size: Black Sea mollusk rapana up to 12 cm high, grape snail - 8 cm, some naked slugs- up to 10 cm, large tropical species reach 60 cm.

A typical representative of the class is big pond snail, living in ponds, lakes, quiet creeks. Its body is divided into a head, a torso and a leg, which occupies the entire ventral surface of the body (hence the name of the class).

The body of the mollusk is covered with a mantle and enclosed in a spirally twisted shell. The movement of the mollusk occurs due to the wave-like contraction of the leg muscles. There is a mouth on the underside of the head, and two sensitive tentacles on the sides, with eyes at their base.

Pond snail feeding plant foods. In its throat there is a muscular tongue with numerous teeth on the underside, with which, like a grater, the pond snail scrapes off the soft tissues of plants. Through throat And esophagus food gets into stomach, where it begins to be digested. Further digestion occurs in liver, and ends in the intestines. Undigested food is thrown out through the anus.

The pond snail breathes with the help of lung- a special pocket of the mantle where air enters through the breathing hole. Since the pond snail breathes atmospheric air, it needs to rise to the surface of the water from time to time. The walls of the lung are woven with a network blood vessels . Here the blood is enriched with oxygen and carbon dioxide is released.

Heart The pond snail consists of two chambers - atria And ventricle. Their walls alternately contract, pushing blood into the vessels. From large vessels through capillaries blood enters the space between organs. like this circulatory system called open. From the body cavity, blood (venous - without oxygen) is collected in a vessel approaching the lung, where it is enriched with oxygen, from where it enters the atrium, then into the ventricle and then through arteries- vessels carrying oxygen-enriched blood (arterial) flows to the organs.

The excretory organ is bud. The blood flowing through it is freed from toxic metabolic products. These substances are excreted from the kidney through an opening located next to the anus.

The nervous system is represented by five pairs nerve ganglia located in different parts bodies, from which nerves extend to all organs.

Pond fish are hermaphrodites, but they undergo cross-fertilization. Eggs are laid on the surface aquatic plants. Young individuals develop from them. Development is direct.

Gastropods include slugs, named because of the abundantly secreted mucus. They don't have a sink. They live on land in damp places and feed on plants, mushrooms, some are found in vegetable gardens, causing harm to cultivated plants.

Herbivorous gastropods include grape snail, also harmful agriculture. In some countries it is used as food.

Among the many species gastropods especially known for beautiful shells- sea. They are used as souvenirs, buttons are made from the mother-of-pearl layer, and some peoples of Africa and Asia make money and jewelry from the shell of a very small cowrie mollusk.

Class bivalve- exclusively aquatic animals. They pump water through their mantle cavity, selecting nutrients. This way of eating is called filtering. It does not require special mobility of organisms, so representatives of the class exhibit some simplification in structure compared to representatives of other classes. All mollusks of this class have bivalve shell(hence the name of the class). The shell valves are connected by a special elastic ligament located on the dorsal side of the mollusk. Muscles are attached to the shell valves - contactors, their contraction helps bring the valves closer together, closing the shell; when they relax, the shell opens.

Representatives of this class are , pearl barley, oysters, mussels. The biggest sea clam — tridacna, weighing up to 300 kg.

The most common mollusk in fresh water bodies of the country is. The toothless body, consisting of torso And legs, covered with a mantle hanging from the sides in the form of two folds.

Between the folds and the body there is a cavity in which there are gills And leg. Toothless has no head. At the posterior end of the body, both folds of the mantle are pressed against each other, forming two siphon: lower (input) and upper (output). Through the lower siphon, water enters the mantle cavity and washes the gills, which ensures respiration. Various simple unicellular algae and the remains of dead plants are brought with water. Filtered food particles enter the mouth through the stomach And intestines where they are exposed enzymes. The toothless has a well developed liver, the ducts of which flow into the stomach.

Bivalves are used by humans. Mussels and oysters are eaten; others, for example, are bred to produce pearls and mother-of-pearl: pearl mussels, pearl barley.

Class Cephalopods

Modern cephalopods There are about 700 species, exclusively inhabitants of seas and oceans with a high concentration of salts, so they are not found either in the Black or Azov Seas.

Cephalopods are predators of medium or large sizes. Their body consists of torso And big head, the leg turned into tentacles that surround horn. Most of them have 8 identical tentacles, e.g. octopuses or 8 short and 2 long, like squid.

On the tentacles are suckers, with the help of which prey is retained. Only one has no suction cups tropical look - nautilus, but has a large number of tentacles Representatives of the class have large eyes, resembling human eyes. Below, between the head and body, there is a gap connecting to the mantle cavity. A special tube opens into this gap, called watering can, through which the mantle cavity connects with the environment and is a modified part of the leg.

Many representatives of cephalopods do not have a shell, only in the cuttlefish it is located under the skin, and in the nautilus there is a multi-chambered shell. The body is located in one of them, the others are filled with air, which contributes to the rapid buoyancy of animals. In many cephalopods, thanks to their jet mode of movement, the speed reaches 70 km per hour (squids).

The skin of many cephalopods can instantly change color under the influence of nerve impulses. Coloration can be protective (camouflaged to match the color of the environment) or threatening (contrasting color, often changing). This is due to the high level of development nervous system, which has a complex brain, protected by a cartilaginous shell - “ scull", sensory organs that determine complex behavior, in particular, the formation of conditioned reflexes.

For example, in case of danger salivary glands secrete a poison that kills prey, or the ducts of the ink gland secrete a liquid that forms a black spot in the water, under its cover the mollusk runs away from enemies.

Cephalopods are dioecious animals. They are characterized by direct development.

Cephalopods are of great industrial importance: they are used as food (squid, octopus, cuttlefish); brown paint, sepia, and natural Chinese ink are made from the contents of the ink sac of cuttlefish and squid. In the intestines of sperm whales, a special substance is formed from the undigested remains of cephalopods - ambergris, which is used in the perfume industry to impart stability to the smell of perfumes. Cephalopods are a food source for marine animals - pinnipeds, toothed whales, etc.

Mollusks are soft-bodied animals. Most species of this type live in the aquatic environment, but there are also representatives that have mastered the terrestrial habitat.

Body structure

The body is not divided into segments. Main sections: head, torso, leg. Some species have no head.

Organ of movement – leg

The leg is a muscular outgrowth of the abdominal wall. With its help, these invertebrates move slowly.

Mantle

One of the main features of the type of mollusk is a special fold - the mantle - lining the shell. The space between the mantle and the body has the appearance of a cavity and is called the mantle. It contains gills and other internal organs.

Sink

The shell is a protective formation that develops on the dorsal side of the mollusk. The shell is formed by two layers.

The nervous system consists of the peripharyngeal nerve ring. One or two pairs of nerve ganglia are connected by jumpers. The sense organs are represented by cells that determine the chemical composition of the aquatic environment and the organ of balance.

Most mollusks are marine animals.

Respiratory system

Shellfish breathe through gills, extracting oxygen from the water. Other species living on land have re-established aquatic environment, have a respiratory organ - the lungs.

Circulatory system

The circulatory system is not closed. In the process of movement, blood enters the body cavity, supplies the internal organs with oxygen and returns to the heart. The organ of blood circulation is the heart. It consists of sections: 1st ventricle and 1st or 2 atria.

Digestive system

Part digestive system includes the pharynx, esophagus, and intestines. There are digestive glands - the liver. Mollusks have a special organ for erasing the top layer of plants - a grater with horny teeth.