Habitat for squid. Deep sea squid suffer from hard mating. Names of squid in different languages

This species lives in the Mediterranean and eastern regions of the Atlantic Ocean from the North Sea to the coast of West Africa. Found in the Irish Sea, along the south coast of England and off the north coast of Scotland. The common squid inhabits different depths up to 100 meters, but can also be found deeper up to 500 meters.

Description

The body is cylindrical in shape, the length of the fins is 2/3 of the length of the mantle, their shape is diamond-shaped. The eyes are large and covered with a transparent membrane. There are 10 tentacles. Of these, 2 tentacles are noticeably longer than the others and are used to capture prey. The standard length of the mantle is 15-25 cm, but can grow up to 30-40 cm. The usual length with tentacles is 50 cm. Males grow faster than females and are larger. The color of the body is gray or reddish.

Reproduction and lifespan

The breeding season for common squid accounts for most of the year, but the peaks are observed in early summer and early autumn. There are up to 20 thousand eggs in the clutch. They are distributed over gelatinous formations of an oblong shape, resembling outwardly long thin sausages. They are attached at a depth of up to 35 meters to fixed and solid objects. It can be rocky rocks, debris on the bottom, dead organic remains, heaps of sand or stones.

The length of the incubation period depends entirely on temperature. At a temperature of 22 degrees Celsius, it is 25 days. And at a temperature of 12-14 degrees Celsius, it reaches 40-45 days. The hatched larvae reach a length of 1 cm and are similar to adults. They grow quickly. For example, in those hatched in June, the length of the mantle reaches 12 cm by December. And in a year it grows up to 20 cm. The common squid lives 2-3 years. Males grow faster and live longer than females.

Behavior and nutrition

In summer, representatives of the species mainly stay at a depth of 20 to 80 meters. In winter, they go deeper to 250 meters and even up to 500 meters. The population living in the northeastern waters of the Atlantic winters near Portugal and Morocco, and in the spring moves to the French coast and further to the North Sea in May - June. In autumn, the opposite is observed.

In the Mediterranean Sea, common squids do not migrate, but dive in late autumn to a greater depth than in summer. The diet of these mollusks mainly consists of fish. Other cephalopods, crayfish, annelids, sea arrows are also eaten. Representatives of the species also attack their fellows, that is, they are prone to cannibalism.

This type is commercial. It is an integral part of the diet in Europe. Therefore, every year these cephalopods are caught in large quantities. Only in the Adriatic Sea between Italy and the Balkans they catch up to 1.5 thousand tons of common squid per year. It is easy to catch them, as mollusks live in large flocks, and therefore the cost of catching is low.

Catching squid and octopus for most people living in the CIS, with the exception of residents of the Far East of Russia, is still a real exotic, more relevant for tourist trips to hot countries, where they can offer any fishing for money, including hunting for cephalopods shellfish during the day and evening. Often there is an impression that squids and octopuses themselves are not a cult object of amateur fishing in Russia and the CIS countries due to the fact that they are extremely rare in the daily diet. Well, admit it, when was the last time you ate squid or octopus? Half a year ago?! That's it!

Based on the foregoing, everyone who has caught, catches and continues to constantly catch squid and octopus for a drive and for a great lunch or dinner deserves all respect and careful listening to the methods of harvesting these cephalopods using completely different devices and devices. Below in the text, we will give the floor to a sea fishing professional, as well as a passionate lover of squid and octopus hunting Igor King of Red Woman’s Heart, and now we will make a small digression, talking about potential fishing targets from a scientific point of view.

The main types of squid caught in the oceans

squids

scientific classification

Kingdom: Animals Type: Mollusks Class: Cephalopods Subclass: Coleoids Superorder: Ten-armed (molluscs) Order: Squids

Latin name

Teuthida

Suborders and families

Loliginidae Australiteuthidae Ancistrocheiridae Architeuthidae (Giant squid) Bathyteuthidae Batoteuthidae Brachioteuthidae Chiroteuthidae Chtenopterygidae Cranchiidae (cranchiidae) Cycloteuthidae Enoploteuthidae Gonatidae Histioteuthidae Joubiniteuthidae Lepidoteuthidae Lycoteuthidae Magnapinnidae Mastigoteuthidae Neoteuthidae Octopoteuthidae Ommastrephidae Onychoteuthidae Pholidoteuthidae Promachoteuthidae Psychroteuthidae Pyroteuthidae Thysanoteuthidae Walvisteuthidae

Names of squid in different languages:

The name of the country	The name of the squid in the local language
Albanian	callamari
Albanian	kalmari
Albanian	lignja
Albanian	ulignja
Basque	txipiroiak
Catalan	calamar
Czech	krakatice
Danish	oligo
Dutch	gewone pijlinktvis
Dutch	pijlinktvis
English	Cape Hope squid
English	common squid
English	European squid
English	inkfish
English	lon-finned squid
English	sea ​​arrow
Finnish	kalmari
French	calmar
French	calmar community
French	encornet
alician	lura txibia
German	Gemeiner Kalmar
German	gewohnlicher Kalmar
German	Kalmar
Icelandic	smokkfiskur
Italian	calamaro
Italian	totariello
Modern Greek (1453-)	Καλαμάρι
Polish	kal amarnice
Portuguese	lula-comum
Portuguese	lula-vulgar
Romanian	calmar
Scottish Gaelic	scuid
Slovak	kalmary
Slovenian	lignji
Spanish	calamar
Turkish	kalamar

squid(name in Latin Teuthida- called in the world scientific classification (taxonomy) a detachment of decapod cephalopods living in the oceans. Typically, squids caught commercially in the Pacific and Atlantic have a size of 0.25-0.50 m, but giant squids living at great depths (up to 7-8 thousand meters) of the genus Architeuthis can reach a length of 20 meters (including tentacles) and are the largest invertebrates in the animal kingdom.

Squids live in almost all climatic zones, including the Arctic, but are most often found in temperate and subtropical waters. Squid living in the northern seas are small in size compared to their southern relatives and mostly do not have a bright color. Squids have five pairs of arms. The fourth pair has lengthened in the process of evolution. The location of the suckers on the arms (tentacles) of squid often varies and depends on the species. Squids have a streamlined torpedo-shaped body, which allows them to move in the water column with a high speed “tail” forward, the main method of movement is jet.

European squid

Loligo vulgaris
scientific classification Kingdom: Animalia Phylum: Mollusks Class: Cephalopods Order: Teuthida Genus: Loligo Species: Common squid Binomial name Loligo vulgaris

A cartilaginous “arrow” runs along the entire body of the squid, supporting the body. It is called the gladius and is a vestige of the inner shell. The coloration of squids is extremely diverse, and depends on many factors: water temperature, depth of the water column, behavior (aggression, fear, etc.). It is noteworthy that some deep-sea squid species have an almost transparent body. The common loligo squid (Loligo vulgaris), of the Loliginidae family, of the genus Loligo, is a species of cephalopod mollusks from the order of ten-armed (Decapodiformes) most famous and widespread in commercial and amateur fishing. The popularity of this type of squid in the Mediterranean countries is so great that it is often called European squid there - European squid, catching only in the Adriatic annually from 1200 to 1500 tons of these individuals for the culinary needs of Italy, Slovenia, Croatia and Albania.

The length of the body of a loligo with tentacles in commercial catches often does not exceed 50 cm, and its weight is 1.5 kg. The length of the mantle is, as a rule, about 20 cm, but can also reach 40 cm, and the males of this species of cephalopods are larger than the females. This species is distributed in the coastal waters of the eastern North Atlantic from the North Sea to West Africa, as well as in the Mediterranean and Adriatic Seas. Loligo keeps at a depth of about 100 m or more, but can also be found at a depth of 400 to 500 m. Loligo squid breeding in the North Sea (the northernmost part of the range) begins in early spring after dark. Cephalopods arrive there in early June.

The loligo clutch consists of several oblong, sausage-shaped eggs, which are attached to a fixed substrate at a depth of about 30 m. These can be parts of the seabed, for example, a rocky ridge with seaweed, or sheer rock outcrops at shallow depths. At the same time, several animals prefer to lay their eggs in a common place. Larvae are morphologically similar to adult specimens, differing in the ratio of body parts to each other. Their size at the time of emergence in June is less than 1 cm. The period of embryo development until hatching at a temperature of more than 20 ° C is from 20 to 30 days, at a temperature of less than 15 ° C - from about 40 to 50 days.

Another extremely important commercial object of world fisheries is Argentine squid ( Illex argentinus) , of the genus Illex, from the Ommastrephidae family, is extremely popular with amateur anglers in Argentina and Uruguay.

Todarodes pacificus
(STEENSTRUP, 1880)
scientific classification Kingdom: Animals Phylum: Mollusks Class: Cephalopods Order: Squids Family: Ommastrephidae Genus: Todarodes Species: Pacific squid

In the Far East of Russia, of particular importance in the domestic fishery of all types of hydrobionts living in the Pacific is Pacific squid (lat. Todarodes pacificus) - a species of cephalopod mollusks from the order of ten-armed (Decapodiformes). The Pacific squid prevailing in catches usually has a size of 0.25 - 0.5 m, but can reach a length of 75-82 cm (including tentacles). This species of squid is found throughout the Japanese, Yellow, East China Seas, off the eastern coast of the Japanese Islands to the island of Okinawa, in surface layers of water to depths of no more than 200 m at a temperature of 0.4-28°C. In warm years, the northern boundary of the squid distribution expands to the Commander Islands, mass accumulations are observed up to 57°N. The Pacific squid feeds on large zooplankton and small fish. Sexual maturity occurs at the age of one year. It is believed that all squid of this species die after the first spawning. The Pacific squid is extremely popular among the inhabitants of Primorsky Krai and Sakhalin Island, who, along with catching ordinary sea fish, constantly catch squid, fishing from boats and boats in the Sea of ​​Japan and the Sea of ​​Okhotsk.

Berryteuthis magister
(Berry, 1913)
scientific classification Kingdom: Animals Type: Mollusks Class: Cephalopods Subclass: Coleoids Superorder: Ten-armed Order: Squids Family: Gonatidae Genus: Commander squids Species: Commander squids

A very significant place in the catches of Russian sailors is commander's squid(lat. Berryteuthis magister), of the genus Berryteuthis and the family Gonatidae, which currently prevails on the shelves of Russian stores and is one of the cheapest cephalopods of all available in retail. The maximum length of the Commander squid is 42-43 cm, and the weight can reach 2.2-2.6 kg. Sexual maturity occurs when reaching a length of 20-25 cm in males and 25-30 in females. Lives up to 2 years.

The Commander squid, reaching the usual size of 25-35 cm in length and weighing from 300 g to 1 kg, constantly lives at a depth of 30 to 1200 m. Juveniles are often found near the surface, adults stay near the bottom, but make daily migrations, rising at night into the water column. The squid feeds on small fish and zooplankton, does not disdain its own young, and itself serves as prey for large fish, sea birds, toothed whales and fur seals. The main fishing areas for the Commander squid are the Seas of Okhotsk, the Bering Sea and the Sea of ​​Japan. Commander squid (about 30,000 tons per year), Russian vessels are harvested by bottom trawl during migration from the Pacific side of the Kuril Islands. There are very few places convenient for trawling, so the entire Russian fishing fleet gathers in small “patch patches”. Although the bottom there is plowed by trawls, the vast majority of other squid habitats are not affected by fishing. Significant stocks of the Commander squid are protected in the zone of the Commander State Reserve. At present, its main catch by the domestic fleet is carried out in only two areas on the Pacific side of the Kuril chain: near the islands of Ketoi and Simushir, Paramushir and Onekotan, since most other places where concentrations of Commander squid are formed are characterized by a complex bottom topography with numerous outcrops of sharp rocks, which limits the possibility of using bottom trawls, which are currently the only fishing gear for Russian vessels in the squid fishery. In the Kuril waters, it is timed to coincide with two spawning seasons and is conducted mainly in March-July and September-January.

Commander squid, caught by Russian vessels, processed on mother ships and sold on the territory of the Russian Federation with entrails, has the most disadvantageous presentation. Despite this, the Commander squid, according to many restaurateurs, is considered one of the most delicious of all other cephalopods caught in other regions of the world. Peruvian squid (Dosidicus gigas) - for example, without special processing it is inedible due to the strong ammonia taste. Therefore, caught squid of this species (in Peru, the Central Reserve Bank confirmed since 2011 that squid has become the second leading category of the Peruvian seafood sector after anchovies), after freezing and briquetting, they are sent for processing to China, from where they are shipped around the world already cleaned.

Are there squids in the Black Sea?

A lot of completely different people in Russia, including amateur fishermen, often worry about a rather interesting question - are there squids, octopuses, cuttlefish and other cephalopods in the Black Sea? No, no cephalopods have been found in the Black Sea, and they are unlikely to appear there in the very near future. Why? I explain. According to ichthyologists, the main reason for the absence of squid, octopuses and cuttlefish in the Black Sea is the low salinity of the latter (from 12 to 22 ppm), which is much lower than the average salinity of the World Ocean (from 30 to 38 ppm). In the best case, even if some individuals of cephalopods get through the Bosphorus from the Sea of ​​Marmara to the Black Sea, they cannot survive there for a more or less long time. On average, a 1.5 kg individual of the Mediterranean Loligo squid (L. vulgaris) after being in an aquatic environment with a salinity of 14-18 ppm can die in about 1-2 hours. Also, all cephalopods cannot bear offspring in the Black Sea water basin due to low salinity, which completely prevents the development of their offspring. It is gametes, eggs (spores, eggs in the case of algae) and larvae of marine organisms that die - the most unprotected, vulnerable stages of the life cycle. Of course, squids do not reproduce using fertilized eggs.

Mating in cephalopods consists in the fact that the male passes the spermatophore to the female (this is a bag of sperm that looks like a narrow tube). They can be from a few millimeters to more than a meter. The spermatophore has a complex shell and an intricate apparatus for ejecting sperm at the signal of a sensitive hair, with the help of a powerful muscular spring and a special secret that instantly glues living tissues together in an aquatic environment with a salinity of 28 to 42 ppm. In an aquatic environment with low salinity (from 12 to 22 ppm), fertilization by the usual method does not occur, since the adhesive secret cannot provide the necessary adhesion. The spermatophores are located in a special organ (needham sac) in the male, and he passes them to the female with a specially modified hand (it is called "hectocotyl"), which is equipped with special clamps or tweezers to firmly grab the spermatophore and pass it to the female, placing it in the exact place where needed. The female squid can carry spermatophores for many months (up to six months), choosing the right moment for fertilization. Then she instructs the spermatophore to release sperm and "hatch" the fertilized eggs until her death. It should be noted that if fertilization in squid individuals occurred in the Black Sea, then the development of the eggs themselves in an aquatic environment with low salinity is virtually impossible.

On the example of eggs from ordinary fish, you can imagine how and why this happens. The egg (although they are large) is just one living cell, it has a more or less strong, depending on the type of animal, protective shell surrounding the cell membrane, consisting of two mobile, fluid layers of lipids; a variety of special proteins are built into the membrane - they carry substances and salt ions through the membrane, perform other functions. On the outside, cell membranes are reinforced and protected by more rigid, branched carbohydrate (sugar) molecules. For the question - why the caviar of hydrobionts of the World Ocean with a higher salinity dies in the low-salinity Black Sea - it is important to know the following.

Ions of some salts (we remember that salts in solution break down into charged halves - positively charged - metal cations, and negative - anions) can penetrate the cell membrane unhindered, but most of them are transported through specially regulated ion channels - large protein molecules similar to tubes that pierce the membrane, and with the help of real, energy-requiring protein machines - ion pumps. This complex system is needed to ensure that the concentrations of various ions necessary for its normal life are always maintained in the cell. But water molecules pass through all cell membranes freely, and faster than ion pumps work. The total concentration of ions of all salts and the sum of the charges of other molecules in the caviar is the same as in its native sea water. This sum of charges is a more accurate and important value than the concentration of salts, but usually, the total concentrations of salts in the egg and the water around it are close. Now we can imagine the following. a pair of sea urchins crawled into the Black Sea, or a pair of swordfish sailed - and spawned. The concentration of salt in the caviar is close to oceanic, and the salinity around is half as much. What will happen? What physicists and chemists call the phenomenon of osmosis will happen: particles (molecules, ions) of a substance always move to where their concentration is lower. Ions cannot pass through the membrane, but water can; the concentration of water in sea urchin eggs, squid eggs is lower than in the Black Sea water, which means that water will rush into the cell. A cell - an egg - will first swell, and then burst. Therefore, squids can appear in the Black Sea for an extremely short time, but they will not be able to reproduce. If they do not develop special adaptation to low salinity conditions - as, for example, it happened with the Pacific snail, which breeds beautifully in the Black Sea water basin.

Squid breeding

LOVE at squids? I also have tenderness ... These are not cuttlefish for you, in which the male ahead of time chooses the best part of the bottom, protects it from other males, lures the female and, dressed in the most catchy colors, beautifully looks after her. And not octopuses, in which the male specifically demonstrates to the female various details of his body so that she learns that he is quite ready for an important service and cannot be eaten immediately, except perhaps after mating, but it can last (for example, in a giant North Pacific octopus from the Far East). East) for more than an hour1... The mating of squids, of course, those that have been studied, in duration approaches a fleeting air battle: they flocked - mated - scattered ... And no ceremonies! Therefore, when my colleague, the famous polar explorer Igor Melnikov, returned in the summer of 1992 from a drifting ice floe from Antarctica (from the American-Russian drifting station "Weddell-I") and said that they were there on an ice floe, in a hole, they caught two squids with a net and soon they will be brought, - I could not even think what a cruel squid love will be revealed to me. But in order!

Mating in all cephalopods consists in the male transferring one or more spermatophores to the female. A spermatophore is a tube-like bag of sperm. Spermatophores can be short or long (from a few millimeters to more than a meter, usually centimeter in size). And this is not just a tube with sperm, but a cunning device with a complex shell and a very intricate apparatus for ejecting sperm, equipped with a sensitive hair, a powerful spring and a tube of glue that attaches life to life, and even in the aquatic environment (just a surgeon's dream!) . Spermatophores are located in a male in a special organ (needham sac) ending in a penis, which can also be a simple tube or a complex apparatus. And he transfers them to the female in some species with a penis, in others - with a specially modified hand; it is called a “hectocotyl” and is equipped with special clamps or tweezers to firmly grasp the spermatophore emerging from the funnel (an open conical tube on the underside of the head - the nozzle of the cephalopod jet propulsor) and transfer it to the female, placing it exactly where it is needed.

This place is quite definite and each species of squid has its own: in some, spermatophores are placed under the mouth with a parrot beak typical of squids, in others they are located on the oral membrane, in a ring around the mouth, in others - near the gills, on the inner wall of the mantle (the muscular shell of the body, for which squids are valued, because they eat it), in the fourth - on the back of the head, in a special hole. However, it seems that there are also such species of squid in which the male does not care where to stick the spermatophores - even on the head, even on the tail, just to unload.

Whether the spermatophores are placed in a special hole, glued to the inside of the mantle or distributed around the mouth - in any case, after leaving the body of the male, they come into contact with sea water, and then a process begins, called the spermatophoric reaction, or more simply - the explosion of the spermatophore. A sensitive hair tears a thin membrane, and sea water enters the membrane of the spermatophore by osmosis. But the shell is strong, two-layer, water presses on the spring, compresses it, and in the end the outer shell does not withstand and breaks at the front end of the spring. The spring flies out, pulls out the inner shell containing the sperm, and the tube of glue attaches it to the skin of the squid. There, the sperm calmly waits for spawning, which squids have only once in a lifetime. Squid can mate just before spawning, being quite sexually mature, and maybe long before spawning, two or three months, while still completely immature. In this case, there are no males at the spawning ground at all, by that time, perhaps, they are no longer in the world.

This is the female laying eggs. If the spermatophores are glued near the gills, the eggs pass by them immediately after leaving the oviducts; if the spermatophores are located on the back of the female's head, the eggs are swept out with two threads through two holes on the sides of the neck, to the right and left of the nape, but if they are swept out through the funnel, then they pass by the ring of spermatophores around the mouth. One way or another, the eggs are sure to be at the place where the sperm is stored, and fertilized.

Rapid mating in squids is really like air combat. In both cases, success is technically ensured ahead of time: in aviation - by a locator, a computer calculation of launching an attack and the most complex device of a rocket or an air gun, in squids - by the sophisticated structure of the spermatophore and intricate devices for attaching sperm in the right position and keeping it viable condition for 2 - 3 months - without any liquid nitrogen!

Everything seems to be clear. But for some reason, it turned out that not all of them. I just came to work at the Institute of Oceanology of the Academy of Sciences and began to study oceanic squids and octopuses, when two female squids fell into my hands - they were extracted from the stomach of an Alepisaurus fish caught in 1963 in the Indian Ocean, south of Sumatra, by my boss N.V. .Parin. Both squids were completely gelatinous, as if not squids, but jellyfish, and without tentacles. But not because they were gelatinous because they were overcooked, and not because they lacked tentacles because the fish bit off them: the squids were fresh, all color was preserved, and both had one short strip on their belly. Strange stripes - as if cut with a sharp knife, start slightly retreating from the front edge and go towards the tail parallel to the axis of the body. From each incision, the heads of spermatophores peep out, and what is interesting: the spermatophores themselves are neatly laid under the skin (completely intact!) In the tissues of the mantle, and only their heads (the place where the sensitive hair is attached) and necks (where the spring lies) stick out into the incision. Moreover, all spermatophores are empty, without sperm, only shells. Obviously, the sperm was used for its intended purpose: both females spawned, and they did not have mature eggs.

Such squids have long been described in the literature. It was believed that this is a special genus and species of Chaunoteuthis mollis (mollis is soft in Latin), in which, oddly enough, only females were known, all mature, all gelatinous, all without tentacles and with slits on the belly: who has one slit , to the right or left of the middle of the belly (a - b in the figure), who has two (on both sides). And in the cuts - spermatophores. But this genus and species belong to a family in which all other genera and species are fleshy, with large sharp hooks with tentacles and tentacles. The family is called: hook-bearing squid, Onychoteuthidae. Think: meaty hook-bearing squid, but without meat and hooks. And no males.

How do cuts appear on the belly of the female and how are the eggs fertilized? Various authors suggested that, they say, the male makes incisions with his beak, and the female, sweeping eggs, drives them under her belly, and along the way they are fertilized. Strange: the beak of a squid, like the beak of a parrot, is not a claw; he is good for biting, but not for cutting food, he can tear the soft mantle of the female, but not cut it. The eggs come out through the funnel towards the head, and it is difficult for the female to turn them to the belly, and if she succeeds, how many eggs will be fertilized during such a strange operation?

The common squid (lat. Loligo vulgaris) belongs to the cephalopod molluscs from the Decapodiformes order. It lives in salt waters. Its range lies in the eastern Atlantic Ocean from Ireland to Guinea, including the Mediterranean Sea.

These mollusks are usually found in shallow coastal waters, holding near the bottom or swimming in the water column. In many countries, their meat is considered an exquisite delicacy.

Commercial fishing for squids is carried out at night, when they begin a collective hunt for schooling fish.

Behavior

Common squids annually make seasonal migrations, swimming several thousand kilometers in search of food-rich areas of the oceans. In summer, they stay close to the surface of the water, and in winter they plunge into the depths.

Usually squids drift at a depth of 20-50 m, but individual individuals have been caught even at a depth of 500 m. These molluscs can lead both a solitary lifestyle and gather in fairly large groups. Groups hunt together, as if surrounding flocks of small fish with a dense hunting net.

During the day, squids lie quietly on the seabed, hiding in stones or in algae, and with the advent of darkness, they turn into energetic predators.

They grab their prey - fish and crustaceans - with two long tentacles and kill with poison, after which they methodically tear off piece by piece and swallow it with pleasure.

Squids themselves are a favorite delicacy of many marine life. Dolphins and sperm whales especially like to feast on them. To save their lives, they learned to change the color of their body and, as it were, dissolve in water, becoming invisible.

In the event of a threat, the mollusk shoots a stream of dark liquid at the aggressor, which envelops him in a kind of smoke screen. After such a chemical attack, he manages to hide from a dangerous predator in a matter of seconds.

Swimming in the water column, squids slowly flap their fins. To develop greater speed, the squid sucks water into the mantle cavity with rhythmic muscle contractions and pushes it out through the siphon with force, thereby creating a strong jet thrust.

Representatives of the species Loligo vulgaris, who prefer a solitary lifestyle, having met a smaller relative, often eat it without much remorse.

reproduction

Common squid breed throughout the year. They have a pronounced sexual dimorphism - males are much larger than females. Having met a female ready for spawning, the male begins to persistently swim around her, trying to demonstrate all his charms and virtues.

The female lays eggs in lumps hidden in gelatinous capsules and sticks them to underwater rocks, algae or objects drifting in the water. Often many females prefer to spawn as a group in one place.

Squid larvae are similar to adults, differing from them only in the ratio of body parts to each other.

At first, young squids with a body length of about 1 cm swim near the surface of the water in friendly flocks and feed on plankton. They grow very quickly and soon begin to hunt small crustaceans and small fish.

Description

Adult individuals reach a body length of 30-50 cm and a weight of up to 1.5 kg. The long body has a streamlined shape. The upper side of the body is colored reddish-brown.

Small dark specks are scattered on the lighter background of the lower side. The mollusk has 10 tentacles: 8 short and 2 long prehensile. Each of the tentacles is equipped with suction cups.

Between the tentacles and the head, clearly separated from the rest of the body, there is a mouth opening with strong jaws, with which the squid can easily crush the shells of its victims. In the pharynx is a special grater for grinding food.

The underdeveloped shell in the form of a horny shelf is completely hidden by the folds of the mantle. On both sides of the body are 2 sail-like fins.

A siphon is located on the underside, through which water is pushed out of the mantle cavity, creating jet thrust. This species has very large eyes, which are the most perfect organ of vision among all invertebrates.

The life expectancy of ordinary squids on average does not exceed 2-3 years.

shellfish- multicellular, three-layer animals with bilateral (bilateral) symmetry of the body, having a mantle (large skin fold) surrounding the base of the body.

Type Mollusks have about 130 thousand species.

Modern scientists in the type of Mollusks distinguish classes : pit-tailed, furrow-bellied, armored (chitons), monoplacophores, bivalves, spadefoots, gastropods (snails), cephalopods (octopuses, squids, cuttlefish).

Malacology(from the Greek malakion - mollusk and logos - word, doctrine) - a branch of zoology that studies mollusks.

Conchology(conchiliology) (from the Greek konche, konchylion - shell and logos - word, doctrine) - a branch of zoology that studies shells (mainly mollusks).

Features of the external structure

have a soft body enclosed in a shell

have a bilaterally symmetrical body structure, i.e. folded according to the principle of mirror reflection - the left half of the body fully corresponds to the right half. However, in the process ontogeny in some species, displacement or uneven growth of organs is observed, which leads to asymmetry. Asymmetry is especially pronounced among gastropods.

the body does not have segmentation. Consists of three sections: head, legs, torso.

the trunk contains all the main internal organs.

have a mantle - an epithelial fold that completely or partially covers the body, connects it with the external environment. In the mantle cavity are located the mantle complex of organs: the excretory tracts of the reproductive system, the excretory tracts of the digestive system, ctenidium, osphradius and the hypobranchial gland. The complex also includes the kidneys and pericardium.

the secondary cavity (as a whole) is represented by the cavity of the heart sac (pericardium) and the cavity gonads.

Features of the internal structure

Organ system	Characteristic
digestive	Open. Consists of the pharynx, esophagus, stomach, middle and hindgut ( rectum). The hindgut opens with an anus into the mantle cavity. Most mollusks are characterized by the presence in the pharynx of a special apparatus for grinding food - radulae. Food types: Filter feeders- toothless, barley. Herbivorous - pond snails, coils. Predators - squid, octopus, cuttlefish.
circulatory	Open (with the exception of cephalopods). It consists of the heart (1,2, sometimes 4 atria and ventricle) and blood vessels. The color of the blood is bluish (due to hemocyanin, a copper-containing respiratory pigment).
Respiratory	Represented by gills and lungs.
excretory	Presented by the kidneys (1 or 2).
	hermaphroditic(snails) or dioecious (toothless).
	In the lower groups, it consists of a peripharyngeal ring and four trunks (tetraneural type of the nervous system). In higher ones, it consists of ganglia (3 or more pairs) and a well-developed supraesophageal ganglion ("brain") - a scattered-nodular type of nervous system.
sense organs	Smell and taste are not separated. The organs of touch are scattered over the surface of the body - on the tentacles, mantle.
Type of development	Direct or indirect. Larvae - trochophora or sailboat (veliger).

Consider examples .

Bivalves	Toothless, barley, oysters, mussels, tridacna, pearl oysters, scallops, shipworms, guidac.
Gastropods (snails)	Sea limpets, livebearers, helmet snails, abalones, grape snails, coils, pond snails, slugs, ambers and more. others
cephalopods	Octopus (common octopus, blue-ringed octopus), squid (common squid, giant squid - colossal squid), cuttlefish (common cuttlefish, Australian giant cuttlefish), etc.

Aromorphoses that contributed to:

unsegmented body

the appearance of a complex fold - the mantle and the mantle cavity

shell formation

Idioadaptation that contributed to biological progress:

shell appearance

the emergence of a device for grinding food - radula

the emergence of two forms of respiration - gill and pulmonary

high fecundity

Consider a brief description of the external and internal structure For example oysters.

External structure
Sink	Thick-walled and uneven. Bivalve.
	Is absent ( reduced)
	Available in juveniles. Absent in adults. Reduced (disappeared), because lead a sedentary life.
	open, siphons does not form.
Internal structure
Organ system	Characteristic
digestive	Vegetable food - algae, ciliates, animal food - rotifers and larvae of coelenterates, worms, mollusks.
circulatory	Open. The heart is two-chambered.
Respiratory	Gills - consist of two thin plates covered with ciliated hairs that maintain a continuous flow of water around the body. Thanks to the action of all these shimmering hairs, the animal constantly receives fresh water rich in oxygen, organic matter and microorganisms.
excretory	Paired modified kidneys that excrete liquid metabolic products into the mantle cavity.
	Dioecious. Fertilization and development of eggs occurs in the mantle cavity. The larvae are mobile, have one leg, which is completely reduced after 72 hours; disappears.
	3 pairs of ganglia: cerebropleural, pedal, visceroparietal. Scattered-nodular type of the nervous system.
sense organs	Weakly developed. There are no head tentacles or eyes. There is statocysts and osphradia.
Type of development	With metamorphosis, i.e. with the passage of the larval stage - glochidia.

Footnotes

1. Idioadaptation- private adaptation of organisms to a certain way of life in specific environmental conditions.

2. Aromorphosis- a progressive evolutionary change in the structure, leading to a general increase in the level of organization of organisms.

3.Bilaterally symmetrical(bilateral) animals are multicellular animals in which the left side of the body mirrors the right side of the body.

4.Gonads- animal organs that produce sex cells - gametes. The female gonads are the ovaries, the male gonads are the testes. Produce sex hormones - androgens and estrogens.

5.ctenidia- the primary organs of gas exchange in mollusks.

6.Radula(grater) - an apparatus used for scraping and grinding food from mollusks. Located in the oral cavity.

7.Hemocyanin- respiratory pigment from the group of metalloproteins, contains copper and is an analogue of hemoglobin.

8.Filter feeders- mollusks that use a passive feeding method, in which organic particles and microorganisms enter the gill cavity through the siphon, are swallowed using two pairs of oral lobes located at the front end of the body.

9.Reduction in biology - reduction, simplification of the structure or disappearance of organs due to the loss of their functions in the process of evolution.

10.Statocysts- mechanoreceptor organs of balance in invertebrates, which look like bubbles immersed under the cover of the body, or straps or flask-shaped protrusions of the cover (in jellyfish and sea urchins).

11.Osphradius- the receptor organ of molluscs, formed by a specialized sensitive epithelium.

12. Ontogenesis- the individual development of the organism from fertilization (during sexual reproduction) or from the moment of separation from the mother individual (during asexual reproduction) to death.

13. Segmentation in morphology: the same as metametry: the division of the body or individual organs into repeating segments (body parts).

14. Pericardium(pericardial sac) - the outer connective tissue membrane of the heart, normally separated from the epicardium by a gap filled with serous fluid - the pericardial cavity.

15. Hermaphrodite- an organism that has the characteristics of a male and female, including and having both male and female genital organs.

16. Siphon- an organ of bivalve molluscs, which is an outgrowth of the siphonal (posterior) edge of the mantle.

17. Receptors(from Latin receptor - receiving), in physiology - the endings of sensitive nerve fibers or specialized cells (retinas of the eye, inner ear, etc.) that convert stimuli perceived from the outside (exteroceptors) or from the internal environment of the body (interoceptors) into nervous excitation transmitted to the central nervous system.

18. Epithelium in animals and humans (epithelial tissue) - a layer of closely spaced cells covering the surface of the body (eg, skin), lining all its cavities and performing mainly protective, excretory and absorbing functions. Most glands also consist of epithelium. In plants, cells lining the cavities of organs or their parts (for example, resin canals in conifers).

More details:

Type Shellfish, or Soft-bodied, - a large group of non-segmented secondary cavities, the body of which consists of a head, trunk and legs. The trunk forms a leathery fold - mantle . She shapes sink . Between the body and the mantle is mantle cavity . About 130 thousand species belong to the type of mollusks.

General characteristics of the type

Some of the shellfish bilaterally symmetrical animals. However, gastropods developed a swirling shell, and their body became secondarily asymmetrical.

Mollusks are characterized by hard mineral shell covering the body of the animal from the dorsal side. The shell, as a rule, consists of crystals of calcium carbonate. From above, it is usually covered with a horn-like organic substance, and from the inside it is lined with a hard, shiny calcareous layer - mother-of-pearl . The shell can be solid, bivalve or consisting of several plates (for chitons). In slow moving and immobile molluscs, the shell is highly developed. However, in some mollusks it is reduced (underdeveloped) or absent altogether. This happens when the mollusk lives in places where it is difficult for predators to reach (for example, when it burrows deep into the sand of the seabed or drills holes in the trunks of trees that have fallen into the sea). Mollusks that swim well have lost their shells.

shellfish body consists of a non-segmented trunk, head and legs. Head found in almost all molluscs. It has a mouth opening, tentacles and eyes. Leg mollusk - a muscular unpaired outgrowth of the body. Usually it is located on the ventral side and is used for crawling.

In bivalve mollusks, due to a sedentary lifestyle, the head is missing, the leg is partially or completely lost. In some species, the leg can turn into a swimming organ (for example, in cephalopods).

Internal structure. The body of mollusks is surrounded by a skin fold - mantle . The space formed between the walls of the body and the mantle is called mantle cavity . In the mantle cavity are the respiratory organs - the gills. The external openings of the excretory organs, the genitals and the anus open there.

Mollusks have in general - secondary body cavity. It is well expressed in the embryonic state, and in adult animals it is preserved in the form of a pericardial sac and cavity of the gonad. All spaces between organs are filled with connective tissue.

Digestion. The mouth opening leads into the pharynx. In the pharynx of representatives of many species there is grater (radula) - a special apparatus in the form of a tape, lying on the ledge of the bottom of the oral cavity. There are teeth on this tape. With the help of a grater, herbivorous mollusks scrape off food from plants, and predatory molluscs, in which the teeth of the radula are larger, strike and seize prey. In some predatory mollusks, salivary glands open into the oral cavity; the secret of the salivary glands contains poison.

The pharynx passes into the esophagus, followed by the stomach, into which the liver ducts open. The stomach passes into the intestine, ending in the anus. In bivalves that feed on microscopic algae and small organic particles suspended in water, the structure of the oral apparatus is simplified: the pharynx, grater and salivary glands are lost.

Breath. In most mollusks, the respiratory organs are paired external gills - flat skin outgrowths lying in the mantle cavity. Land snails breathe with lung - modified mantle cavity.

Circulatory system. The heart of mollusks consists of one ventricle and two atria. Circulatory system open . Some mollusks have manganese or copper in their blood, the compounds of which play the same role as iron in the blood of higher animals - they provide oxygen transfer.

excretory organs represented paired kidneys , which at one end communicate with the cavity of the pericardial sac (the remains of the coelom), and at the other end open into the mantle cavity.

Nervous system. The central nervous system consists of several pairs of ganglia (nodes) connected by nerve trunks, from which nerves extend to the periphery.

Sense organs. Mollusks have well-developed organs of touch, chemical sense and balance. Motile mollusks have organs of vision, and fast-swimming cephalopods have well-developed eyes.

Reproduction. Most shellfish dioecious . However, there is also hermaphrodites in which cross-fertilization occurs. Fertilization in mollusks is external (for example, in oysters and toothless) and internal (at grape snail).

From a fertilized egg, either a larva develops, leading a planktonic lifestyle (the so-called sailboat ), or a formed small clam.

Origin. There are several points of view on the origin of molluscs. Some zoologists believe that flatworms were the ancestors of mollusks. Others suggest that molluscs are descended from annealed worms. Still others think that mollusks originate from ancestors common with annelids. Embryological data indicate the relationship of mollusks with annelids.

A typical mollusc larva (sailfish) is very similar to annelids larvae, carrying large lobes lined with cilia. The larva leads a planktonic lifestyle, then settles to the bottom and takes on the appearance of a typical gastropod mollusk.

The value of shellfish

Representatives of some classes of mollusks are of great importance in many natural biocenoses. Aquatic mollusks are often the most numerous group in benthic ecosystems. The filtration method of feeding bivalve mollusks leads to the fact that many of them precipitate mineral and organic particles, providing water purification. Mollusks feed on fish, birds and animals.

Mollusks serve as food for people and are traditional objects of fishing and breeding. (oysters, scallops, mussels, cockles, squid, Achatina, grape snail).

In the shells of sea mollusks pearl oysters very beautiful pearls are formed. sinks kauri were used by the natives as coins. From the shells of fossil mollusks, geologists can accurately determine the age of sedimentary rocks.

Mollusks (soft-bodied) are animals with a soft, non-segmented body, having a shell or its remains. Most mollusks have a head, a body, and a muscular leg. Under the shell is a skin fold - the mantle. The circulatory system is not closed. Most mollusks are dioecious, but there are also hermaphrodites. More than 130 thousand species of mollusks are known.

Mollusca type includes 7 classes: Shellless, Monoplacophora, Shellfish, Spadefoot, Gastropoda, Bivalves and Cephalopoda.

Class Gastropoda (Gastropoda)

gastropods (they are also called snails) - the most numerous and diverse class of mollusks. It has about 90 thousand species.

Habitat. In the lakes, ponds and river backwaters of our country you can meet one of the representatives of this class - big pond snail (5) about 5 cm long. In the forest litter, in damp meadows, in gardens and orchards, another species is found - naked slug (4) up to 12 cm long.

External building. The pond snail has three distinct body parts. These are the head, leg and bag-shaped torso. From above, the body of the mollusk is covered with a special fold of skin - mantle . In a naked slug, the body is elongated, and the body and mantle are small.

The pond snail has a spiral, twisted in 4-5 turns shell that protects the body of the animal. The shell is made of lime and topped with horn-like organic matter. In connection with the spiral shape of the shell, the body of the pond snail is asymmetrical, since in the shell it is also curled into a spiral. The initial narrow and blind end of the shell are called summit , and open and wide - mouth shells. The shell is connected to the body by a powerful muscle, the contraction of which draws the cochlea into the shell. In a naked slug, the shell has been reduced (disappeared) in the process of evolution.

The leg of the pond snail and slug is muscular, well developed and has a wide sole . A characteristic way of movement of these animals is to slowly slide on the foot over plants or soil. The abundant mucus secreted by the skin glands of the foot facilitates smooth gliding.

When crawling, the muscles of the leg of the cochlea contract in waves from the anterior end of the sole to the posterior; the speed of such movement in terrestrial gastropods is from 4 to 12 cm per minute.

In gastropods, leading a floating lifestyle, the leg turns into fins and blades. Among these mollusks there are walking, jumping and swimming individuals.

Digestive system. In the mouth, on a special mobile outgrowth resembling a tongue, there is a grater ( radula ) with horny denticles. With their help, the pond snail and slug scrape off their food: the pond snail - soft parts of plants and microscopic algae on underwater objects, and the slug - leaves, stems, berries of various land plants and mushrooms. There are salivary glands in the pharynx, the secret of which is processed food. From the pharynx, food enters the stomach through the esophagus. The ducts of the liver flow into it. The secret of the liver dissolves carbohydrates, the absorption of food also occurs in the liver. The stomach passes into the intestine, which makes several loops and ends with an anus at the front end of the body above the head (in the pond snail) or on the right side of the body (in the slug).

Respiratory system. In terrestrial and some freshwater molluscs, the gills are replaced by an organ of air respiration - easy . The free edge of the mantle fuses with the body wall, leaving a small breathing hole leading into the mantle cavity. Numerous blood vessels develop in the mantle, and the mantle cavity becomes the lung cavity. This is how the lung is formed. In the lung, gas exchange occurs - the saturation of the blood with oxygen and its release from carbon dioxide.

For breathing, a pond snail living in water is forced to periodically rise to the surface of the reservoir and change the air in the lung cavity through the respiratory opening.

Most aquatic gastropods breathe with feathery gills . In connection with the asymmetry of the body, there is an underdevelopment of the organs of the right side of the body. Therefore, in most gastropods, the right gill disappears and only the left remains.

Circulatory system. The pond snail and the slug have a heart, consisting of an atrium, a ventricle, and blood vessels. The circulatory system in gastropods open : blood flows not only through the vessels, but also in the cavities between the organs. Departs from the heart aorta , it branches into arteries , after which the blood enters the small cavities located among the connective tissue. There, the blood gives off oxygen and is saturated with carbon dioxide. Next, the blood goes venous vessels to the lung, where the blood is enriched with oxygen and getting rid of carbon dioxide. The blood then flows through the veins to the heart. The heart rate in gastropods is 20-40 times per minute.

excretory system. Due to the asymmetry of the body, the pond snail and the slug retain only left kidney . At one end, this kidney, through a wide ciliated funnel, communicates with pericardial sac (the remainder of the body cavity), where metabolic products are collected, the other - opens into the mantle cavity on the side of the anus. The pericardial sac is the remnants of the coelom. Therefore, we can say that the excretory systems of mollusks and annelids are similar in structure.

Nervous system mollusks of scattered-nodular type. It consists of several large ganglions interconnected by nerve bridges, and numerous nerves. In connection with the twisting of the body of gastropods, the nerve bridges between some nodes form a decussation.

Sense organs. On the head of both the pond snail and the slug there are organs of touch - tentacles. The pond snail has one pair, the slug has two. There are eyes. In the pond snail they are at the base of the tentacles, and in the slug they are at the tops of the second pair of tentacles. The second pair of tentacles is the organ of smell. In addition, gastropods also have balance organs.

Reproduction. Fertilization in a pond snail and a slug internal . Both of these animals hermaphrodites . In the only sex hermaphrodite gland, both spermatozoa and eggs are formed.

Fertilization in these mollusks is cross: each of the mating individuals plays the role of both male and female, therefore, the exchange of genetic material of different individuals occurs. From the laid fertilized eggs, small molluscs develop, similar to adult animals.

Development. A larva (sailfish) develops from eggs in marine gastropod molluscs. The larva leads a planktonic lifestyle, then settles to the bottom and takes on the appearance of a typical gastropod mollusk.

Some marine gastropods (eg. trumpeter) serve as objects of fishing. Shells of sea molluscs haliotis give a very beautiful pearl. sinks kauri used as coins. Grape snails are bred as edible animals.

Gastropod mollusks are distributed throughout the globe. Among them there are both marine, and freshwater, and terrestrial forms. The coastal zones of subtropical seas and mountain forests of subtropics and temperate latitudes are the richest in species.

A characteristic feature of gastropods is the asymmetry of the structure. This is the most numerous class of molluscs. The shell is entire, often spirally twisted. Slugs do not have shells. Many gastropods serve as food for fish and birds. Among the gastropods there are pests of gardens and orchards .

The structure of a bivalve mollusk: 1 - the line along which the mantle is cut; 2 - muscle-contactor; 3 - mouth; 4 - leg; 5 - oral lobes; 6.7 - gills; 8 - mantle; 9 - inlet siphon; 10 - outlet siphon; 11 - hindgut; 12 - pericardium

Aquatic mollusks are often the dominant group of benthic biocenoses. M. is an important food object in the diet of commercial invertebrates, fish, and some whales. Edible fish (oysters, mussels, scallops, squid, Achatina, grape snail, etc.) are a traditional object of fishing (about 1.5 million tons are mined annually in the world, according to other data - 5 million tons of various fish. ) and aquaculture (world production in 1985 was about 3.2 million tons). Diff. species of sea pearls are the object of prom. breeding in the Persian Gulf., near about. Sri Lanka, off the coast of Japan. Since antiquity, shells have been used as jewelry, as money, in cult rituals, and in decorative and applied arts. Some M. are included in fouling; stone grinders, shipworm can damage sea vessels, port and other hydraulic engineering. structures; slugs, snails, etc. harm page - x. cultures. Due to overfishing and habitat destruction, many species in need of protection, eg. some tridacnas, cyprees, cones, etc. 19 species of M. in the Red Book of the USSR