How are squids born? squid clam

Mollusks are widespread secondary cavities, invertebrates. Their body is soft, undivided, in most it is divided into the head, trunk and leg. The main features of mollusks are the presence in most species lime shell And robes- a skin fold that covers the internal organs. The oral cavity of molluscs is filled with parenchyma. The circulatory system is not closed. Over 130,000 modern species and about 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 mollusk species, this is the most numerous class. Its representatives are relatively small in size: Black Sea mollusk rapana up to 12 cm tall, grape snail- 8 cm, some naked slugs- up to 10 cm, large tropical species reach 60 cm.

A typical class representative is big pond snail living in ponds, lakes, quiet backwaters. Its body is divided into a head, a torso, and a leg that 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 muscle. A mouth is placed on the underside of the head, and on the sides are two sensitive tentacles, at their base are eyes.

The pond snail feeds on plant foods. In his 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 digest. Further digestion takes place in liver and ends in the intestines. Undigested food is expelled through the anus to the outside.

The pond snail breathes with the help 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 braided with a net blood vessels. This is where the blood is enriched with oxygen and carbon dioxide is released.

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

The excretory organ is bud. The blood flowing through it is freed from toxic metabolic products. From the kidney, these substances are excreted through the opening located next to the anal.

The nervous system is represented by five pairs ganglions located in different parts of the body, nerves depart from them to all organs.

Prudoviki are hermaphrodites, but their fertilization is cross. Eggs are laid on the surface of aquatic plants. They develop into juveniles. Development is direct.

The gastropods include slugs, named because of the abundant secretion of mucus. They don't have sinks. They live on land in humid places and feed on plants, fungi, some are found in vegetable gardens, causing harm to cultivated plants.

The herbivorous gastropods are grape snail also harmful to agriculture. In some countries it is used as food.

Among the numerous species of gastropods, sea shells are especially famous for their beautiful shells. 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 kauri mollusk.

Bivalve class- exclusively aquatic animals. Through their mantle cavity, they pump water, choosing nutrients from it. This type of food is called filtration. It does not require special mobility of organisms, therefore, representatives of the class have some simplification in structure compared to representatives of other classes. All molluscs of this class have bivalve sink(hence the name of the class). The shell flaps are connected by a special elastic ligament located on the dorsal side of the mollusk. Muscles attached to shell valves contactors, their contraction contributes to the convergence of the valves, the closing of the shell, when they are relaxed, the shell opens.

Representatives of this class are , barley, oysters, mussels. The largest marine mollusk tridacna weighing up to 300 kg.

The most common mollusk in fresh water bodies of the country is. The body of a toothless, 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 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 breathing. With water, various protozoan unicellular algae, the remains of dead plants are brought. Filtered food particles pass through the mouth into stomach And intestines where they are exposed enzymes. The toothless is well developed liver whose ducts empty into the stomach.

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

class cephalopods

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

Cephalopods are medium to large sized predators. Their body is made up of torso And big head, the leg turned into tentacles that surround horn. Most of them have 8 identical tentacles, for example octopuses or 8 short and 2 long, like squid.

On the tentacles are suckers, with the help of which prey is retained. Only one tropical species does not have suckers - nautilus, but has a large number of tentacles. On the head of the representatives of the class there are large eyes resembling human eyes. Below, between the head and the body, there is a gap that connects with the mantle cavity. A special tube opens into this gap, called watering can, through which the mantle cavity is connected to the environment and is a modified part of the leg.

Many representatives of cephalopods do not have a shell, only the cuttlefish has it located under the skin, and the nautilus has a multi-chamber 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 the jet mode of movement, the speed reaches 70 km per hour (squid).

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

For example, in case of danger, the salivary glands secrete 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 is made from the contents of the ink bag of cuttlefish and squid - sepia, natural Chinese ink. 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 perfume. Cephalopods are a food base for marine animals - pinnipeds, toothed whales, etc.

The type of molluscs is divided into 7 classes: shellless, monoplacophores, armored, spadefoot, bivalves, gastropods and cephalopods.

Shellless (Aplacophora) mollusks have a worm-like body up to 30 cm long, completely covered by a mantle, there is no shell. On the ventral side, they have a groove with a roller - a rudiment of the leg. There are no nephridia. This group of molluscs are hermaphrodites.

Breeding and breeding squid

Biologist Henk-Jan Hoving from the University of Groningen is interested in how squid reproduce Decapodiform cephalopods. In addition to this cephalopod, Hoving studied at least ten more species of squid and cuttlefish - from a 12-meter giant squid to a mini-squid no more than 25 mm long.

As Hoving says, studying deep-sea squid is still very difficult, because it is very difficult to get to them. To observe these cephalopods in their natural environment requires a special technique. Therefore, the biologist had to reconstruct the sexual habits of squids, content with already dead specimens and descriptions of other specialists. But still, the Dutchman managed to make some discoveries.

As the biologist himself says, "reproduction is not fun, especially if you are a squid."

In the mollusk species Taningia danae, males, during mating, injure the body of females with their beaks and hooks to a depth of five centimeters. And all because this type of squid simply does not have suckers. But from such "self-mutilation" partners derive considerable benefit. In cuts, males put "bags" containing spermatozoa - spermatophores.

The same method is used by representatives of another variety of deep-sea "multi-armed" - Moroteuthis ingens. True, the process of such a peculiar fertilization in these squids is more peaceful. Spermatophores penetrate the skin without damaging it. According to Hoving, the males have some kind of substance, most likely an enzyme, that allows you to "melt" the skin.

Hoving found evidence that spermatophores penetrate the skin on their own. The biologist managed to see this process in freshly caught squid. Moreover, Japanese doctors have registered a case of squid spermatophores growing into human tissue. Not so long ago, in the Land of the Rising Sun, an operation was performed, during which “sperm bags” of a cephalopod were removed from the throat of some sashimi lover.

And here is the mini squid Heteroteuthis dispar decided to raise the birth rate. Females of this species fertilize their eggs on their own, inside the body. According to Hoving, they developed a special pouch for storing sperm, which is directly connected to the internal cavity of the body and reproductive organs.

When mating, males fill this container with sperm. And so generously that its stock can be up to 3% of the body weight of the female. According to the biologist, this method has a lot of advantages for both sexes. Females can grow eggs for a long time and gradually fertilize them as they mature. And the “bombed out” males still have a guarantee that their girlfriends will have completely specific spermatozoa.

Found Hoving among squids and "effeminate" males. Squids are not snails, they usually do not have hermaphroditism. But Ancistrocheirus lesueurii found small glands that are involved in the production of eggs in females. The body length of these non-males also turned out to be not quite standard - more than that of normal "men".

Hoving cannot explain this phenomenon and believes that it is the result of exposure to hormones and hormone-like substances from human pills. Which first with sewage fall into the coastal zones of the ocean, and then to the depths. But, the biologist adds, it may also be the squid's own "invention" - a kind of way to get closer to women.

The scientist hopes that his research will not only help to learn more about deep-sea cephalopods, but will also save them from human greed. After all, not only research probes penetrate into the depths, but also new fishing trawls.

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 mollusks 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 forcefully pushes it out through the siphon, 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.

There are many interesting things in the depths of the sea. The most unusual are the phosphorescent inhabitants of the deep sea. Squid, one of the few animals endowed with such an ability.

The underwater world is a mysterious environment, which has not been fully explored so far. Among the inhabitants of the depths there are creatures that are not only striking in their beauty, but also terrifying in their size and strength. One of these amazing creatures is the common squid - a representative of the order of ten-armed molluscs, belonging to the class of cephalopods.

How to recognize a squid externally?

The average body length of this mollusk is 50 centimeters. One individual can weigh about one and a half kilograms, while females are smaller than males. The body color has gray and red tones. Fins are located on the sides of the body - the common squid has two of them. Therefore, when the fins are in a straightened state, the body takes on the shape of a diamond.

Near the mouth opening, in a circle, there are 10 tentacles equipped with suckers. And in the mantle of the animal there is a special bag with ink, which the squid uses in case of danger. When the mollusk needs to quickly hide from the enemy, it simply releases an inky liquid and swims away from the pursuer, leaving it in a black cloud.

Squid habitats

The eastern part of the northern regions of the Atlantic Ocean (from the western coast of the African continent to the territory of the North Sea) is densely populated by squids, in addition, this animal is found in the Adriatic and the Mediterranean.

The depth of habitat of this animal is up to 100 meters, however, observations of the mollusk showed that it can live at a depth of 400 to 500 meters! The soil prefers muddy or sandy.

animal lifestyle

Squids are migratory mollusks, they travel great distances in search of food. The squid cannot be called either a solitary or a flocking animal, therefore there are both solitary individuals and large groups. If squids gathered in a group and live together, then they hunt together.

Typically, the depth of habitation under water at a common squid is from 20 to 50 meters, however, for the most part, the depth of residence depends on the season: in the summer months, the mollusk swims closer to the surface of the water, and in winter it goes to the depth.

The squid often swims slowly, making graceful strokes with its fins, but, if necessary, it can also develop greater speed: for this, it begins to contract muscles rhythmically, thereby taking in a large amount of water under the mantle, then, by means of a sharp ejection of water, it quickly pushes your body forward.

The diet of squid

The squid is a predator. The basis of his "dining table" is fish. But the squid does not disdain crayfish, polychaete worms, as well as other representatives of the class of cephalopods. Scientists have even recorded cases of cannibalism.

The process of catching food is as follows: with two tentacles, the squid captures the victim, killing it with its poison. After the “food” is immobilized, the animal begins to systematically, slowly, tear off pieces from the victim and eat them.

Shellfish breeding

Immediately after the end of the winter months, the breeding season begins for squids. Breeding consists in the formation of an egg clutch that looks like a sausage. Squids attach their masonry on immovable rocks, and sometimes on the shells of sea mollusks. Often, laying eggs occurs at a depth of up to 30 meters.

Scientific mysticism. In the cuisine of Japan there is a dish "Dancing squid". The clams are placed in a bowl of rice and poured with soy sauce. The dead animal begins to move. Mystic? No. Sauce contains sodium.

The nerve fibers of the squid react to it by contracting. Interaction is possible within a few hours after catching the mollusk from the sea. Have you ever caught a pike?

When carving it after 5-10 hours of lying out of the water, you find that the fish is twitching, and its heart is beating. What about chickens running around after decapitating? So, there is nothing surprising in the posthumous dances of the squid. It is more in the life of the being. Let's talk about her.

Description and features of the squid

It is called the primate of the sea. This speaks to the top rung of evolution that the squid occupies among the cephalopods. In its class, the hero of the article has the most developed brain and even has a cartilaginous likeness of a skull.

Bone formation helps protect the thinking organ. It provides the complex behavior of the squid. The animal is capable of cunning, deceit and other intellectual tricks.

The combination of the brain with other organs and functions of the animal is also a trick. Yes, at giant squid the thought center is shaped like a doughnut. The hole in the center is reserved for the esophagus. In other words, squid - shellfish that eats through the brain.

The mouth of the hero of the article is so powerful that it resembles a bird's beak. The density of the chitinous jaws makes it possible to pierce the skulls of large fish. The thick fishing line is also uneasy for the animal, it bites.

If the mollusk is nevertheless caught and got into the human mouth, embarrassment may occur. Several cases of ejection of sperm by undercooked squids have been recorded. Most precedents are recorded in Japan and Korea. So, in January 2013, the sperm of the mollusk caused the hospitalization of a visitor to one of the restaurants in Seoul.

sea ​​squid in the "dancing" dish came to life when they began to chew it. The animal threw out 12 spindle-shaped sacs with sperm into the mucous membrane of the tongue and cheeks of a restaurant visitor. The foreign substance caused the burning sensation. The woman spat out the dish and called the doctors.

In Russia, no such cases have been recorded. There are regions where squid is a familiar dish, for example, the Far East. However, in domestic open spaces, mollusks are cleaned of internal organs and boiled well. In Asian countries, squids are rarely cleaned.

The squid is classified as a cephalopod due to its body structure. The limbs do not extend from him. The leg, transformed in the process of evolution into 10 tentacles, departs from the head of the animal, surrounding the mouth. The eyes of the mollusk have a familiar arrangement. The structure of the organs of vision is similar to that of a human. At the same time, the eyes are able to follow each different object.

The body of the squid is a muscular mantle with a thin plate of chitin. It is located on the back and is the remnant of the shell. Squids do not need its frame, because they have developed jet propulsion.

By taking in water, contracting the body and throwing out streams, mollusks swim faster than many fish. When spaceships and the first rockets were created, scientists were inspired by squids. Next, details about their lifestyle.

Squid lifestyle and habitat

Flashlights could also be invented by looking at squids. Their bodies are equipped with photophores. In caught molluscs, these are bluish dots on the skin. If big squid, photophores reach a diameter of 7.5 millimeters.

The structure of the "lamps" resembles the device of car headlights, lanterns. Bacteria are the source of light. They feed on squid ink. The mollusk fills the photophores with a dark liquid when it wants to turn off the light. By the way, on the body of one mollusk there can be "lamps" of 10 different designs. There are, for example, "models" that can change the direction of the rays.

Some squids are even named after their ability to radiate. So, in the Gulf of Tayami off the coast of Japan, the Firefly lives. More precisely, the mollusk lives at a depth of 400 meters. The colony is washed ashore in June-July. This is the time of excursions, when tourists admire the bright blue waters of the bay. Scientists, at this time, puzzle over why squids need photophores. There are several versions.

The most real: - the light attracts cephalopod prey, that is, small fish. Second opinion: - the radiance of squid scares off predators. The third assumption about the role of photophores is associated with the communication of mollusks with each other.

400-500 meters - the standard limit of the depth at which it is able to live squid. inhabits below is just a gigantic view. Its representatives are also met at 1000 meters under water. At the same time, the giant squid rises to the surface. Individuals 13 meters long and weighing almost half a ton were caught here.

Most squid live at a depth of about 100 meters, looking for muddy or sandy bottoms. Cephalopods rush to it in winter. In the summer, squids rise to the surface.

Most of the population lives in the North Atlantic Ocean. Here squid fishing carried from to the North Sea. Rich in cephalopods and the Mediterranean.

In the Adriatic, squids are also found. Tracking individuals is difficult as the animals migrate. The stimulus for movement is the search for food. In addition to fish, crustaceans, other mollusks, even relatives are used.

They are caught with two tentacles, injecting a paralyzing poison into the victim. From immobilized squids tear off small pieces of flesh, slowly eating them. Having gained strength and waiting for the summer, squids begin to breed. Fertilization leads to egg laying. It looks like a sausage, with a film on top, and eggs inside. After that, the parents leave.

About a month later, centimeter offspring are born, immediately starting an independent life. It is possible only where the salinity of the water is 30-38 ppm per liter of water. That is why there are no squids in the Black Sea. The salinity of its waters does not exceed 22 ppm.

Types of squid

Let's start with the Pacific squid. It is he who is accustomed to see on the shelves of domestic stores. True, the Russians are accustomed to calling the mollusk Far Eastern, according to the place of catch.

The sizes of individuals start from a quarter and end with half a meter. This is along with the tentacles. Single squids reach 80 centimeters. The species lives at depths up to 200 meters. The desired water temperature is 0.4-28 degrees Celsius.

The second of the main types of squid is Commander. It is also sold in Russia, sometimes ahead of the Pacific in terms of sales volume. The Commander species is smaller, growing up to a maximum of 43 centimeters.

The standard size is 25-30 centimeters. Representatives of the species are distinguished by the ability to swim to depths of up to 1,200 meters. The young are kept near the surface. He, basically, and hits the shelves. The extermination of the species was the reason for the founding of the Commander State Reserve. There, squid fishing is prohibited.

It remains to mention the European squid. Meat one individual weighs up to 1.5 kilos. The body length of the animal, in this case, is 50 centimeters. The species swims to depths of up to 500 meters, usually resting on 100 meters. Individuals have short tentacles, a light body. In the Pacific species, for example, it is gray, while in the Commander it is reddish.

There are also Giant, Peruvian and Argentinean squids. They can only be seen outside of Russia. There was talk of a big one. Peruvian is inedible. Harm squid lies in the ammonia taste and, in fact, the content of ammonia itself in the meat. The Argentine variety is mild in taste but loses it when frozen. Sometimes, Argentine clams are found in canned food.

Squid nutrition

In addition to fish, crayfish, worms and their own kind, the hero of the article catches plankton. Another dietary product associated with the benefits of squid for the environment. Cephalopods feed on algae. Their squids are scraped off the rocks.

This ennobles the appearance of the bottom and prevents the water from blooming. If the target is a living being, the hero of the article hunts from an ambush, tracks down the victim. The poison is injected by the radula. This is a set of teeth in an elastic shell. Not only do they deliver poison, but they also hold prey while it tries to escape.

Reproduction and lifespan of the squid

Squid seed sacs are in a special tube. Could meet her, cleaning the carcasses. The length of the tube is from 1 centimeter to 1 meter, depending on the type of mollusk. Females take seed material in a depression near the mouth, on the back of the head, or in the mouth.

The location of the fossa depends, again, on the species. squid. Price receiving sperm, sometimes, months of gestation. Males do not select girlfriends by age. Often, the semen is transferred to the immature female and stored in her until the reproductive life span is reached.

When children appear, the father may no longer be alive. Most squids die at the age of 1-3 years. Only giant individuals live longer. Their limit is 18 years. Old squids, as a rule, lose their taste, are harsh even with minimal heat treatment. So, young animals try to catch and cook for food. Its meat is considered dietary.

Calorie squid is only 122 units per 100 grams of product. Proteins of them account for 22 grams. Fats are less than 3, and only 1 gram is reserved for carbohydrates. The rest of the mass is water. In the bodies of squids, like most animals, it is the basis.