The pearl oyster is hermaphrodite or not. Essays from the life of freshwater animals (Pavlovsky E.N., Lepneva S.G.). How to determine the original sex of a hermaphrodite

The concept of hermaphroditism originates in ancient Greek legend. Hermaphrodite was the son of two gods - Hermes and Aphrodite. He took his big name from two parents Herm from Hermes and Phrodite from Aphrodite. The parents themselves could not pay attention to Hermaphrodite, so non-poisons took up his upbringing. At the age of 15, he wandered around his native places, and one day the nymph Salmakida, who lived in the water, fell in love with the young man. Once Hermaphrodite went to the source of water in which the nymph lived to quench his thirst. Salmakida saw the young man and immediately fell in love with him. Hermaphrodite also burned with passion for this nymph and asked the gods to unite them into one inseparable creature. The gods granted his request. So, according to legend, hermaphrodites appeared.

How were hermaphrodites treated before?

The phenomenon of hermaphroditism underlies the widespread beliefs about androgynes (creatures that can change their gender). In the Middle Ages, sexual metamorphosis was considered a matter of evil spirits, and the inquisitorial practice of the 16th-17th centuries. rich in cases of persecution of hermaphrodites. So, in Darmstadt in the XVI century. there was a case of the baptism of an infant of dubious sex with the name of Elizabeth, then John, and the subsequent transformation of John again into Elizabeth, who was finally burned at the stake.

Can hermaphrodites have children?

Hermaphrodites, as a rule, cannot have children, they are barren.

How to determine the original sex of a hermaphrodite?

The answer is quite simple - genetically or by chromosome analysis.

Can hermaphroditism be cured?

Many doctors claim that hermaphroditism can be cured, and the sooner such treatment is started, the better - there will be a greater chance of avoiding a double life. The ideal period for eliminating such a problem is considered to be the first years of the child, because it is always psychologically more difficult for an adult to correct this problem consciously. On the eve of the operation itself, the main issue is the choice of hormones that will be administered to the patient, changing his sexual characteristics.

Hermaphroditism is one of the malformations that occurs in one in two thousand newborns.

Who are hermaphrodites from a legal point of view?

This issue has been elaborated in the most detailed way in Muslim jurisprudence. The prescriptions for hermaphroditism are reduced to the following: hermaphrodites approach the male or female sex, according to which they follow the legal position of one or the other sex. If there is no such approximation to one of the two sexes, then they occupy a middle position. During prayer in the mosque, they must stand between men and women and pray like a woman, and during the pilgrimage they must wear women's clothing. As a joint heir, the hermaphrodite receives half the male and half the female part.

Roman law does not allow a middle legal state between the two sexes: the rights of a hermaphrodite are determined by the sex that prevails in him. This principle is followed by modern European legislation (Russian legislation is completely silent about this subject). European legislation leaves parents to decide on the sex of a hermaphrodite; but the latter, upon reaching the age of 18, may himself choose the sex to which he wishes to join. Third parties whose rights are violated by such a choice have the right to demand a medical examination.

Treatment of hermaphroditism is strictly individual. When choosing a sex, the functional prevalence of the female or male body is taken into account. Basically, operations are performed on the external genital organs, but there are cases of operations for the complete elimination of hermaphroditism. After such operations, constant monitoring by specialists is necessary, but in general the prognosis is favorable. Unfortunately, childbearing in such a case is impossible.

Types of hermaphroditism

natural hermaphroditism

Hermaphrodite An organism that has both male and female characteristics, including both male and female reproductive organs. This state of the body can be natural, that is, the species norm, or pathological.

Hermaphroditism is quite widespread in nature - as in flora(in this case, the terms monoecious or polyecious are usually used), and among animals. Most of the higher plants are hermaphrodites; in animals, hermaphroditism is common, primarily among invertebrates (coelenterates, the vast majority of flat, annulated and roundworms, molluscs, crustaceans and some insects).

Among vertebrates, many species of fish are hermaphrodites, and hermaphroditism is most often manifested in fish that inhabit coral reefs. With natural hermaphroditism, an individual is able to produce both male and female gametes, while a situation is possible when both types of gametes, or only one type of gametes, have the ability to fertilize.

Synchronous hermaphroditism

In synchronous hermaphroditism, an individual is able to simultaneously produce both male and female gametes. In the plant world, this situation often leads to self-fertilization, which occurs in many species of fungi, algae and flowering plants.

In the animal kingdom, self-fertilization with synchronous hermaphroditism occurs in helminths, hydras and mollusks, as well as some fish, but in most cases autogamy is prevented by the structure of the genital organs, in which the transfer of one's own spermatozoa into the female genital organs of an individual is physically impossible.

Serial hermaphroditism (dichogamy)

In the case of sequential hermaphroditism (dichogamy), the individual sequentially produces male or female gametes, while there is a change in the phenotype associated with the sex as a whole. Dichogamy can manifest itself both within one reproductive cycle and during life cycle individuals, while the reproductive cycle can begin either with a male or with a female phase.

In plants, as a rule, the first option is common - during the formation of flowers, anthers and stigmas do not ripen simultaneously. Thus, on the one hand, self-pollination is prevented and, on the other hand, due to the non-simultaneity of the flowering time of various plants in the population, cross-pollination is ensured.

In the case of animals, most often there is a change in the phenotype, that is, a change in sex. A striking example are many species of fish, such as parrot fish, most of which are inhabitants of coral reefs.

Abnormal (pathological) hermaphroditism

It is observed in all groups of the animal world, including higher vertebrates and humans. Hermaphroditism in humans is a pathology of sexual determination at the genetic or hormonal levels.

It is interesting! Cleaner fish live in families of 6-8 individuals - a male and a "harem" of females. When the male dies, the strongest female begins to change and gradually turns into a male.

Distinguish between true and false hermaphroditism:

• True (gonadal) hermaphroditism is characterized by the simultaneous presence of male and female genital organs, along with this, there are both male and female sex glands. The testicles and ovaries in true hermaphroditism can either be combined into one mixed gonad, or located separately. Secondary sexual characteristics have elements of both sexes: a low timbre of voice, a mixed (bisexual) type of figure, more or less developed mammary glands.

The chromosome set in such patients usually corresponds to the female set. True hermaphroditism is an extremely rare disease (only about 150 cases have been described in the world literature).

• False hermaphroditism (pseudohermaphroditism) occurs when there is a contradiction between the internal (chromosomal) and external (structure of the genital organs) signs of sex, that is, the gonads are formed correctly according to the male or female type, but the external genitalia have signs of bisexuality. The cause of hermaphroditism anomalies is a failure at the genetic level during the intrauterine development of the fetus. When a child is born, it is determined by its external genitalia whether it is a boy or a girl. Although it is often possible to identify hermaphroditism only when the child begins puberty.

It is interesting! In some species of flatworms, such as Pseudobiceros hancockanus, the mating ritual takes place in the form of fencing with dagger-shaped penises. Being hermaphrodites, both participants in the duel tend to pierce the opponent's skin and inject sperm into it, thus becoming a father.

The pearl thread is the cherished dream of many representatives of the beautiful half of humanity, especially if we are talking about natural mother-of-pearl, which creates a mollusk. Meanwhile, few people know what kind of living organisms on earth produce this amazing biogenic formation and how the body of the pearl mussel works.

Few people know that it is mollusks that produce pearls.

Species Margaritifera margaritifera

In appearance, a completely inconspicuous bivalve shell of black, brown and greenish tones with a glochidia larva hiding in it is the very creator, thanks to which humanity has the opportunity to admire the delicate beauty of freshwater pearls. The common pearl oyster, which is also called European because of its range, is a fairly large mollusk, the dimensions of which often exceed 12 centimeters in length (the record figure was as much as 16 centimeters) and about 5 centimeters in width.

Mollusk range

To date, the pearl oyster mollusk is found mainly in the northern regions. the globe, spreading in small fresh water bodies of the Russian Federation (Valdai, Karelia, rivers flowing into the northern seas), the countries of the Scandinavian Peninsula, Belarus, on the Atlantic coast of France, as well as in the eastern and northeastern parts of Canada and the States. Unlike many other molluscs, pearl shell prefers clean, non-stagnant rivers and streams with a fast current, which has a direct effect on the thickness of its valves, making them lighter and thinner.

At the same time, they manage to lead an almost immobile lifestyle, trying to dive in that bottom part of the reservoirs, where there is a minimum amount of silt and a lot of pure river sand with a rather heterogeneous substrate of pebbles of various sizes. Of great importance for this variety of mollusks is a high percentage of oxygen and a minimum content of salt minerals, which also thin the shell.

And if now such shells are very rare, then even in the last century it was easy to find their numerous populations, whose representatives preferred to dive with a sharp end into the sandy bottom at a depth of 25 centimeters to 2.5 meters or stick around cobblestones located right on the river rapids. For example, in the reservoirs of the Kola Peninsula, researchers counted 70 shells per 1 square meter, but now only memories remain of such a density.

The structure of a river shell

Having figured out where margaritifera margaritifera currently lives, it will not hurt to get acquainted with its structure, which has a number of unique features of its kind. Among them it is worth highlighting:

It should be noted that pearl mussels have the thickest valves, which are forced to live in hard water with a large amount of impurities (does not apply to reservoirs with high salt concentrations, which tend to thin their shells). At the same time, too soft water also does not benefit this organism, thinning its protective layer and leading to the formation of deep erosions in its upper part.

If the pearl river shell constantly lives in water bodies with a low salt concentration, then over time, numerous protein layers called Tulberg's are formed in its thick mother-of-pearl layer.

Scientists note that with aging, the relief of the valves inevitably collapses, and it is more or less possible to observe these bizarre patterns only when studying the youngest representatives of this species.

Lifestyle of a pearl oyster

As already known, the European pearl oyster has been leading an extremely passive lifestyle throughout its entire existence. It is noteworthy that this feature is observed not only in the processes of movement of the mollusk, which are almost completely absent, but also in its nutrition and reproduction. That is, to satisfy its natural needs, this living organism does not have to make almost any effort.

Nutrition and reproduction

The pearl oyster feeds on all kinds of microalgae. and detritus of an organic type, which are filtered by its own gills in the process of breathing. This feature has led researchers to believe that the respiratory and digestive system bivalve molluscs, based on very thorough filtration, are inextricably linked and, in fact, are one. It is noteworthy that in just one day, a miniature shell manages to pass up to fifty liters of water through its gills, receiving with it not only oxygen, but also good nutrition.

The pearl mussel feeds on all kinds of microalgae and organic type detritus

Males do not have to strain too much in terms of reproduction, since all that is required of them is simply to throw away their seed, which tends to spread quite quickly throughout the reservoir, fertilizing females.

Usually this process takes place in mid-August, because it is then that lazy mollusks, without moving a single step from their familiar place, release millions of their spermatozoa, which fertilize the eggs of females through their half-open valves.

The formation of larvae occurs very quickly. By the end of August, there are about three million such babies on the leaf alone. Their further path is determined by instinct, because the female literally throws off a new generation, whose main task is to attach to other inhabitants of the reservoir as quickly as possible. Usually final the mollusk formation phase takes 8 to 11 months, outside the limits of another living organism, their development becomes impossible by definition.

Despite such a primitive device, margaritifera margaritifera boasts a huge amount unique facts from his own life, which amaze the imagination of a simple man in the street. And the most interesting of them are the following:

But the main feature of this freshwater mollusk is its longevity, because the age of some specimens reaches 250 years, which automatically allows the river pearl oyster to be awarded the honorary title of the oldest invertebrate animal.

By taking measures to reduce the capture and breeding of these mollusks, it is possible to preserve and increase the population, thereby ensuring that humanity can continue to admire the exquisite beauty of freshwater pearls.

Hermaphroditism in humans (true) is a pathological disorder of a congenital nature, due to the presence of two types of gonads - testis and ovary (ant. dioeciousness). Sometimes there is also an uncharacteristic gonadal set of mixed structure (ovotestis). Symptoms of true hermaphroditism do not have strictly typical characteristics, it all depends on which gonad in the body is most active. Treatment, causes and diagnosis in each case are different.

In general, "bisexuality" can be described as a malformation of the reproductive system, when double symptoms (men and women) are detected during diagnosis. As a rule, doctors mean its false form when there are signs of the development of the internal gonads of one sex, and the external organs from the other (or with symptoms of an obvious "bisexuality").

Duality: mysticism and reality

Even during the time of complete equality, gender differences have not lost their relevance, and the possibility of combining male and female features in one body is still considered amazing. Pathology has always been covered with a cloud of mysticism, and the very concept of deviation came from ancient Greek mythology as a result of the merger of two names: Aphrodite and Hermes.

The hermaphrodite child has always been treated differently: with fear, with reverence, as a curse or degradation of the family. Diagnosis of the causes, and even more so, the treatment of such "otherness" was not carried out. Fortunately, in the modern world, there is a scientific and reasonable explanation for everything.

True hermaphroditism. In total, there are no more than 200 descriptions of such patients in the world medical practice. Unlikely, more often gynecologists and andrologists describe the symptoms (and causes) of false hermaphroditism: when the subject during diagnosis finds symptoms that determine the simultaneous dichotomy - the gonads of one sex, and the intimate external organs of the other.

True hermaphroditism, morphoforms (classification):

• When the male or female secondary sexual characteristic predominates.
• When obvious signs are revealed in equal "performance" from both sexes.
• When the genital organ of one sex is present, and the gonad is of the opposite (sexual type of transsexualism).

Variants of true hermaphroditism, accompanied by anomalies of the external genitalia:

• A complete set of external intimate organs of a man (woman) with "blotches" of one or more elements from the other sex.
• Incomplete set of genitalia from different sexes.
• A dual and complete sexual set of external intimate organs for both men and women.

But most often, the diagnosis "shows" false hermaphroditism, and it is female, with congenital adrenogenital syndrome.

Why is this happening?

Modern reasons for the birth of children "descendants of Hermes and Aphrodite" are quite prosaic. Spontaneous breakdown in hereditary information during pregnancy, when changes in chromosomes or genes occur (at an early stage of embryo formation), is associated with a number of the following reasons:

• Chemical and toxic poisons (abuse or illegal drugs).
• Irradiation.
• Exposure to biofactors (viruses, bacteria, toxoplasmosis).

• Changes in hormonal balance in the mother and fetus.

An excess of androgens in a female fetus leads to the formation of male-type genitalia and vice versa, when a male fetus with a lack of testosterone develops female intimate signs, which happens when:

• Diseases of the adrenal glands.
• Pathologies of the hypothalamus or pituitary gland.
• Neoplasms in the sex glands.

Despite near-perfect science, the reasons why “bisexuality” develops in its true form are not completely clear. Some scientists suggest hereditary causes, since the diagnosis revealed some nepotism of such a pathology.

What does it look like?

The symptoms of sexual hermaphroditism are not always shown to the world in all their glory; in most cases, an ordinary person may not even guess that best friend or a work colleague is not quite who he claims to be.

The symptoms of the pathology are different and manifest themselves depending on what the causes or form of hermaphroditism were:

• Underdevelopment of the penis.
• Inconsistency of physique and voice (female type) with the indicated gender in the passport (male).
• Changes in the structure of the genital organs or their complete inconsistency with the sex indicated in the passport.
• "Resettlement" of the urethra from the head to other parts of the perineum.
• Early puberty.
• Cryptorchidism, curvature of the penis.
• Developed mammary glands in men.
• infertility, lack of normal intimate life.

False male hermaphroditism is a condition where male genitalia visually resemble female ones due to their abnormal development during fetal life. The child is often recorded as a "girl", the treatment is not carried out, the parents raise him accordingly, but when a fatal mistake is discovered, this brings a lot of psychological problems to the boy with false hermaphroditism.

A few reliable facts about hermaphroditism:

• This condition is more often congenital, in more rare cases, experts are forced to ascertain signs indicating the opposite sex during puberty.
• In adulthood, the symptoms of "bisexuality" appear due to the use of hormonal drugs.
• Sometimes a pathology is not diagnosed for a long period, a person even marries, is quite socially adapted. Diagnosis is carried out for infertility, difficulties in intimate life, with periodic complaints of pain in the abdominal cavity (testicles, male, not descended into the scrotum).
• Sometimes "bisexuality" is combined with mental deviations, mental disorders, which manifest themselves in dementia, increased sexual desire and a complete decline in morality.

But since deviation is a combination of signs of two sexes, with the dominance of both male and female sexual types, there are no exact symptoms of the disease, they will be radically different in each case.

In addition, the symptoms in young children cannot manifest in principle, both in true and false form of pathology, as transvestism, homosexuality, bisexuality or transsexualism. Early detection of the symptoms of hermaphroditism is complex and is entirely the responsibility of pediatricians, who must clearly understand this and know the detailed differences between a possible sexual anomaly. With any suspicion, children are sent for a consultation to the urological or gynecological department. According to the results of the diagnosis, the most justified treatment will be prescribed.

How is the examination carried out?

Diagnostics is carried out according to the following parameters:

• Disease history.
• The course of pregnancy in the mother of the child.
• Were there any abnormalities in the health of the newborn, were there any anomalies.
• At an older age, it is established how the period of puberty proceeded.
• In adult men (women): are there any problems in intimate life, infertility, decreased desire, etc.
• A physical examination will detect the presence of secondary sexual characteristics.
• An examination by a urologist will help determine the presence / absence of a sexual anomaly.
• Karyotyping is a method of studying chromosomes in a person, its quantity and composition, which will allow genetically determining the sex of the patient.
• Diagnostics based on ultrasound, MRI helps to reveal what is hidden during the examination available to the doctor, and to give an accurate conclusion about the true structure of a person.
• Blood and urine test for hormones.

Diagnosis is individual, the patient will have to undergo a full examination using, if necessary, highly specific methods. Treatment consists in the use of hormone therapy and surgical methods.

Therapeutic activities

The treatment of deviation is completely different from the traditionally used therapy and is based on what the diagnosis showed. The principles of treatment combine the basics of hormonal, surgical and psychotherapeutic techniques.

Hormonal treatment includes taking:

• Thyroid-stimulating hormones (thyroid gland).
• sex hormones.
• Means acting on the regulatory function of the pituitary gland.
• Glucocorticoids.

Surgical treatment is carried out depending on which gender will be a priority - according to the male or female type. Psychotherapeutic treatment is necessary in order to form in the "new person" the correct ideas about the chosen field, to correct his behavior, way of thinking, principles of choosing clothes.

Class: Bivalves

Class: Bivalvia, Lamellibranchia Linnaeus, 1758 = Bivalves, laminabranchs

European pearl(L.A. BELOVA, http://bio.1september.ru)

Since ancient times, people have appreciated the beauty of pearls - its smooth matte surface, soft shine. Pearls were used to decorate clothes, household utensils, frames of the most revered icons, and book bindings. Particularly large and regular-shaped pearls were kept in the state treasury as great treasures.

In Russia, starting from the 11th-12th centuries, patterned pearl embroidery on linen, silk, brocade, and velvet was widely spread. Russian craftsmen created unique patterns of pearl embroidery and pearl jewelry. Pearls were used to embroider church items, ceremonial royal, princely, boyar and even folk clothes. They used for such sewing mainly freshwater pearls, which were mined right there, within the limits of the Russian state.

Information about the extraction of pearl nuclei in Russia is available, for example, in documents dating back to the 15th century. Novgorod pearls were especially valuable. its grains were strikingly beautiful. It was Novgorod pearls that Ivan III presented in 1488 to the Hungarian king Matt.

In the XVI century. Varzuga pearls mined in the Varzuga River (Kola Peninsula) began to be in great demand. He was bought to decorate church utensils and clothes. The area near the city of Kem was famous for its especially abundant pearl fishery. In 1788, this city was given a coat of arms depicting a wreath of pearls on a blue field of water. freshwater pearl oyster

European, or common, pearl oyster (Margaritifera margaritifera)- freshwater bivalve mollusk, a relative of the well-known barley. Its shell is dark, elongated, with a well-developed mother-of-pearl layer on the inner surface. The shell can be up to 12–13 cm long and about 5 cm wide. Atlantic Ocean. “There is no country in Europe that would be rich, like Russia, in rivers and rivulets in which pearl shells are found,” wrote in the 80s. of the last century, Russian geologist A.A. Stuckenberg1.

Even at the beginning of the twentieth century. in many rivers of the Kola Peninsula and Karelia there were many pearl mussels, which were actively hunted. However, in the future, due to overfishing and pollution of rivers with industrial waste, the number of mollusks began to decline rapidly. Now this species is included in the Red Book of the Russian Federation.

In addition to our country, the European pearl mussel is found in the rivers of Finland, Sweden, the mountainous regions of Central Europe, and very rarely - in Norway, the Baltic countries, in the UK, in northern France. However, all European populations are under the threat of complete destruction. Over the past 30 years, about half of them have disappeared, and most of the remaining ones have ceased to be reproduced.

Zhemchuzhnitsa adheres to places with a fast current, it is found at rapids, rifts and reaches with a sandy-stony bottom, but it avoids silted reaches with a weak current. The mollusk lives at a depth of 0.3 - 2.5 m, burrowing into the ground with the front end of the shell and exposing the rear end with siphons. It feeds on unicellular algae and organic detritus, which it extracts from the water by filtering it through the gills. In suitable places, the density of shells sometimes reaches 70 pieces per square meter. And each mollusk passes through itself more than 50 liters of water per day, which makes it possible to purify it to crystal clearness.

Salmon now spawns in 33 rivers of the Kola Peninsula, but only in one - Varzuga - it is plentiful. Why was Varzuga the most productive? A survey of the river showed the presence of a large population of pearl mussels - about 80 million individuals. This is now the largest population in the world - the rest number from 10 to 100 thousand individuals. According to rough estimates, the pearl mussels in Varzuga precipitate about 200 tons of suspension per day, perfectly purifying the water.

There are three reasons for the extinction of the pearl mussel and a decrease in the number of salmon: excessive fishing for shellfish, no less excessive production of salmon fish, pollution of rivers. And along the Varzuga, they don’t raft the wood, there are no industrial enterprises here, the river is difficult to access for mass poaching. It turns out that optimal conditions have been preserved here for both salmon and pearl mussel.

But along with the passive protection of rivers, active measures are needed to restore the abundance of the pearl mussel. One way is to relocate adults to rivers where pearl mussels did not live before or where they disappeared from. However, it is necessary to take into account not only the suitability of aquatic biotopes, but also the presence of natural hosts of glochidia in them. So, in 1933, from the Zhemchuzhny stream near Kandalaksha, the pearl oyster was transferred to the streams of the Pertozero basin, where salmonids were not found, and acclimatization was not successful.

Scientists believe that simultaneously with the resettlement of sexually mature pearl mussels, glochidia should also be resettled. Artificial infection with glochidia could increase the efficiency of reproduction thousands of times. To do this, pearl mussels are collected, their shells are slightly opened, the sex and maturity of females are determined, they are marked and placed in cages before spawning. The resulting suspension of glochidia is injected into the mouth of the caught fish without removing them from the water. After 18 days, in the experiments, from 2 to 10 thousand larvae were noted, fixed on one salmon. As already mentioned, such infection is practically harmless to fish.

The restoration of the pearl oyster population can be combined with the resumption of the extraction of freshwater pearls, excluding the destruction of mollusks. However, this is a matter for the future, and first it is necessary to restore the number of pearl mussel and salmon.

And what is a pearl, for the sake of which freshwater pearl mussels have been so mercilessly caught for many centuries? The pearl consists of the same substance as the shell, i.e. mainly from calcium carbonate. The inner layer of the shell is mother-of-pearl, a derivative of one of the purine bases - guanine. Mother-of-pearl is formed by the thinnest layers lying in several layers, which create interference of light rays, as a result of which the mother-of-pearl layer shines, shimmering with all the colors of the rainbow. A pearl, as is known, is formed after some foreign object, for example, a grain of sand, gets into the wall of the mantle or into the mantle cavity, around which mother-of-pearl begins to be deposited.

Sometimes the pearl grain adheres to the inner surface of the shell. Then it does not form a round beautiful core and it can be difficult to separate it from the wall. Such pearls are called half pearls. The pearls that form on the body of the mollusk are usually ball-shaped and are called pitched. It is these pearls that are especially highly valued. In the shell, as a rule, there is one pearl. The quality of pearl grain does not depend on the size of the shell and the beauty of its mother-of-pearl layer. Quite often, in beautiful and large shells, uneven, low-value pearls were found ...

This order includes 13 families of mollusks, which are very different in the structure of their shell and body, as well as in distribution and lifestyle. At the same time, they are united by a greater or lesser reduction of the anterior closure muscle, which can either be greatly reduced in size ( Unequal muscle- Anisomyaria), or there is only one large closing muscle, usually located in the middle of the shell ( single muscle- Monomyaria).

Often this whole detachment of ligamentous teeth called unequal muscle. The absence of a real lock is common to the entire order, but some (Mytilidae) have tooth-like outgrowths under the umbo under the umbo. The valves are connected to each other mainly with the help of a ligament (ligament). The gills are filamentous (Filibranchia), consist of two folded (outer and inner) sheets (semi-gills) on each side of the body. They are formed by long pubescent cilia, thin bent gill filaments, forming first descending and then ascending knees. Separate gill filaments do not grow together, but only interlock with each other with the help of hard cilia sitting on special disks. The ascending and descending limbs of the gill filaments can grow together with connective tissue bridges only at the points of their fold or at the ends of their ascending limbs.

Almost all ligamentous teeth are forms of epifauna, that is, they live on the surface of the soil, attaching to it with their byssus or even growing with a valve to stones and rocks, or lie freely on the surface of the soil and can even swim; some of them live partially "stuck" in the ground. Young forms usually move freely with the help of their legs, which are usually reduced in adults. All of them are active filter feeders.

From this detachment, we will consider only some of its representatives, which are interesting from the point of view of their structure, lifestyle, or economic significance.

The family Mytilidae includes many common species: mussels, modiol, musculus, mytilasters etc., widely distributed in the seas of the globe, mainly in their shallow areas. All of them have a wedge-shaped "mytilid" type shell; the anterior closing muscle is small and narrow, while the posterior one is large and rounded.

The most widely known mussels, many species of which are edible and commercial: edible mussel(Mytilus edulis), Far Eastern giant mussel or black shell(Crenomytilus grayanus), mediterranean-black sea mussel(M. galloprovincialis), Californian(M. californianus), Mussel Magellan(M. magellanicus) and others.

Mussels are common inhabitants of the coastal zone, where they often form mass settlements. Merging with each other byssus, they form the so-called brushes on the banks; their large concentrations in the littoral and in underwater shallow waters in the more open parts of the sea are called median banks.

Mussels have an elongated wedge-shaped shell, narrowed in front, widened behind. In connection with their attached mode of life, the umbo is shifted to the anterior (pointed) end of the shell. The color of the shell is dark, often blue-black, the inner surface has a thin mother-of-pearl layer. There are several small lock teeth; the byssus is well developed.

The gland that secretes the byssal threads lies in mussels in a small finger-like leg, which in adult mussels, due to their immobile lifestyle, has almost completely lost its motor function. Young mussels (less than 1-2 cm long) can move well, which can be seen when observing them in an aquarium. Adult mussels change their habitat only under very unfavorable conditions, cutting off the byssus and moving to a new place. The strong byssus threads enable them to withstand even the strongest surf, and only the blows of the waves of the strongest storm can break the bundles of mussels, devastating their settlements. Only a network of remains of byssal threads on the rocks, the remains of shells and a broken shell indicate the places of their recent dense settlements.

The byssal gland consists of two parts: one lies in the depths of the leg, at its base, and the other at its anterior end. The substance of the thread secreted by the first part of the gland enters the groove that runs along the lower surface of the leg to its top. Here it sticks to the substrate with a special attachment disk, which is secreted by another part of the gland. The threads of the byssus are attached to the substrate in a certain order and by their tension, like anchors, hold the animal. In addition, mussels for retracting the legs have several pairs of muscles attached from the inside to the valves. With their contractions, the mollusk is pulled up and pressed against the substrate, and not just hanging on the threads of the byssus, so even with very strong surf, the mussels do not break on the rocks.

Mussels are dioecious, but their sex can only be determined in young forms by the color of their maturing gonads, partially lying in the folds of the mantle: in males of an ordinary edible mussel, the mantle is cream, and in females it is orange-red, and in the Far Eastern giant mussel, respectively white and pink color. Mussels breed in the warmest time of the year. Fertilization of eggs occurs in water, where sexual products are thrown.

The fecundity of mussels is very high and increases with age. Usually, during each laying, the female mussel throws from 5 to 12 million eggs, and large specimens - up to 25 million. The female giant mussel begins to breed in the sixth year of life (the life expectancy of this mussel is about 20 years), each time laying about 20 million. eggs. Approximately 20 hours after fertilization, a trochophore larva appears from the egg, which, after two swimming days in the water column, turns into a sailboat larva (veliger). Under unfavorable conditions for settling, the duration of the planktonic (floating) stage of life of the larvae of the sailboat can be greatly delayed from several days to several months. With a size of 0.2-0.3 mm, the veliger settles to the bottom, already having 2 pairs of gill filaments. For some time, the young mussel still crawls along the bottom, but then it is attached by the byssus. Young mussels are usually found in large numbers in thickets of littoral algae, which protect them from drying out during low tide.

By the end of the first year of life, mussel fry off the coast of Europe reaches 3-4 cm in length, and in the White Sea - only 0.5 cm; mussel lives up to 13-14 years.

The food of mussels is detritus (remains aquatic plants and animals), as well as single-celled algae and small planktonic animals and bacteria living in the water column. At a temperature of about 20 ° C, one mussel (5-6 cm long) can filter about 3 liters of water per hour; a dense settlement of mussels on a bank can filter from 50 to 280 m3 of water per day. Thus, large mussel settlements are a powerful biofilter that sucks out a large amount of suspended matter, both mineral and organic, and small plankton from the surrounding water. At the same time, food particles are sorted out and sent to the mouth opening, while heavier and mineral particles are removed in the form of pseudofeces. Thus, mussels, like many other bivalve molluscs (ligamentous, the vast majority of odd-toothed and comb-toothed), are active filter feeders. They not only purify the surrounding water from suspension, but with their pseudofeces and feces they take part in the formation of silty soils. Mussels usually eat all year round but less intense in winter.

Mussels have many enemies among marine fish, birds and mammals. Birds hunt them at low tide in the littoral. Mussel banks in shallow areas are severely affected by stingrays, flounders and cod, and in the Black Sea - by sturgeon fish. But their constant enemy, usually living in the areas of mussel settlements, are large sea ​​stars that feed on them, as, for example, in the Atlantic -Asterias rubens, and in Far Eastern seas- A. amurensis, Patiria pectinifera, etc. One star eats daily on average one or two mussels up to 2 cm in size. They are also hunted by crabs, large gastropods, etc.

ordinary edible mussel(Mytilus edulis) is one of the most widespread bivalve species; it is a variable species, forming ecological and physiological races. She lives off the Atlantic coast of Europe, off the coast of Iceland, South Greenland, along the Atlantic and Pacific coasts of Canada and the USA, lives in the Barents, White and Baltic Seas, in the southwestern parts of the Kara Sea and in the Far East Seas.

Large settlements of common mussel are observed mainly in the littoral (tidal) zone, where twice a day these mussel settlements dry out during low tide. However, by tightly closing their valves at this time, they manage for 5-6 hours with the amount of water that remains in their mantle cavity. The density of settlements of the common mussel can reach several thousand specimens, and the biomass can reach several kilograms per 1 m2.

The common mussel is a euryhaline form, i.e. it tolerates significant fluctuations in salinity and desalination up to 3°/00. However, if it constantly lives at low salinity, as, for example, in the Baltic Sea, then it grows more slowly and becomes smaller. Thus, the size of adult mussels at a salinity of 2 and 3°/0° in the Gulf of Bothnia is 4-5 times smaller than that of those living at a salinity of 15°/00 in the Danish straits and in the Bay of Kiel.

The common mussel is also very eurythermal, i.e., it can endure significant temperature fluctuations: in the summer in the littoral at low tide, it can be very warm by the sun, and in winter, in the harsh conditions of the Bely and Barents Seas mussels can even freeze through while remaining alive. However, apparently due to the abrasive action of ice covering the littoral in winter in the eastern parts of the Barents Sea and in the adjacent parts of the Kara Sea, mussels live here not in the dry zone, but at a depth of several meters.

Far East giant mussel(Crenomytilus grayanus), reaching 20-25 cm in length, lives in the Sea of ​​Japan, off the coast of Sakhalin and Northern China. It lives on the most diverse, mainly on stony-sandy soils, at a depth of up to 50-60 le, often forms large settlements - banks, growing together with byssus into druze; its biomass can reach 20 kg per 1 m2 of soil or more.

In the 20-30s, the giant mussel, along with oysters, was brought from Japan to California, where it took root.

Mediterranean-Black Sea mussel(Mytilus galloprovincialis) is very variable in the shape of its shell, forming a number of subspecies. In the Black Sea, it occurs at a salinity of more than 10 ° / 00 on various soils and depths - from rocky and from the water's edge up to soft silty soils and depths of about 80 m. At a depth of 50-80 m in the Black Sea, the biocenosis of "mussel silt ”, where one of the varieties of the Black Sea mussel (v. frequens) is the leading form. The biomass of bottom fauna here reaches 0.5 kg per 1 m2.

Since ancient times, mussels have been of commercial importance for humans, as evidenced by the remains of their shells (together with oysters), which form the so-called "kitchen heaps" of ancient human settlements since the Stone Age.

Annual global production of mussels (mainly edible) in last years increased to 2-2.5 million centners.

Thanks to the large reserves of mussels in our seas, the development of their fishery in the USSR has great prospects. The total stocks of mussels off the Black Sea coast of the USSR are, according to rough estimates, about 65 million tons, and about 7 million tons available for fishing, or about 800 thousand tons in terms of meat. Kamchatka, however, their fishing here is still insufficiently developed. In the White Sea, the reserves of mussels only in the area of ​​the Karelian and Pomeranian coasts amount to about 3 thousand tons.

Mussels are caught with special toothed dredges from small motorized boats or collected by divers.

Due to the fact that in many countries the natural stocks of mussels are significantly undermined and threatened with extinction, such as in France, they began to be bred artificially. There are such "mussel parks" in Normandy and other regions. There they often grow better than on natural, "wild" banks. There are several ways to artificially breed mussels. Usually they are brought up on special wattle fences (“busho”), standing in the water, where the collected juveniles are transferred. Here, mussels grow for 1.5-3 years to their best taste. On the coast of France, mussels bred in this way annually produce about 8 tons of meat per 1 hectare; at present, it is believed that with intensive culture, up to 150 kg of mussels can be obtained from one linear meter of such a wattle fence. So, in Italy, in the Gulf of Taranto, with a productive culture of mussels, an average of more than 1 ton per 100 m2 is obtained.

Mussels are eaten fried, boiled and canned (raw mussels quickly deteriorate and become poisonous). The nutritional value of mussels is high: fresh mussel meat contains about 10% proteins, 1% fats, 0.5% carbohydrates (glycogen), as well as vitamins B and C, and many different salts useful for the human body.

Small mussels are also used to make a very nutritious fodder meal, which is used for pet food.

The genus Modiolus is close to mussels; interesting in their way of life are also the views from genus musculus(Musculus, or Modiolaria) and stone grinders(Lithophaga), often also called "sea dates".

The most famous in the northern parts of the Atlantic and Pacific oceans is a large warm-water common modiola(Modiolus modiolus), up to I a length (usually 5-8 cm). It has a light brown convex shell, pubescent behind with leathery outgrowths of periostraca. It lives mainly on hard rocky-sandy soils; at a depth of up to 100 m in the Barents Sea, it forms a very characteristic rich epifauna biocenosis.

Phaseolin modiola-Modiolus (Modiolula) phaseolinus has a small bean-shaped brown shell and is well known, for example, in the Black Sea, where it forms mass settlements at a depth of 60-120 m, due to which this zone was called "phaseolin", and soils with the remains of shells - "phaseolin silt".

Some species of modiola can weave a kind of nest from their byssus, plastered on the outside with pebbles and fragments of shells. Similar "nests" can be built from the threads of their byssus and pieces of algae by species from the genus Musculus close to the modiols. In such a "nest" Musculus discors hides the mucous cords of its oviposition. A similar “nest” is made by black muscle (M. nigra) from pieces of zostera sea grass (according to observations off the coast of Denmark). In both species, the embryos develop in these nests without passing through the free-swimming larval stage, as in other mytilids. Thus, the construction of these "nests" is one of the types of care for their offspring.

An interesting example of the active settlement of marine organisms in a new reservoir is the history of the appearance of a mollusk in the Caspian Sea. mytilastera(Mytilaster lineatus, or Brachyodontes lineatus). This is a small mollusk about 2 cm long, with a dark wedge-shaped ("mytilid") shell, with a strongly developed byssus. The castle consists of 2-3 teeth located under the top of the head; dorsal margin finely serrate from inside.

In the 20s of our century, mytilaster was accidentally brought here, perhaps on the bottoms of wooden ships transported by land from the Azov to the Caspian Sea, where he found very favorable conditions existence (both in terms of salinity - 10-12 ° / 00, and nutrition), quickly multiplied and widely settled. Now, at depths of up to 50 m, it has become the most numerous component of the benthic fauna in most of the Caspian Sea. In some places in the Middle and South Caspian, it makes up more than two thirds of the total biomass of the benthic fauna, and its own biomass can reach several hundred grams per 1 m2, and sometimes even more than 1 kg per 1 m2. In a number of areas of the Caspian Sea, even the displacement of some local species of mollusks by mytilaster is sometimes observed.

Curious in lifestyle sea, or stone, dates from genera Litofaga(Lithophaga) and Botula(Botula). They have a low elongated shell with smooth or striated valves covered with thick periostrac. They lead a “hidden” way of life, turning passages and minks in limestone and rocks, where they live, attaching to their walls with byssus and exposing their long siphons. Therefore, finding and collecting them is very difficult. Often they live together with other molluscs, such as folads. Well-known species such as mediterranean lithophea(Lithophaga lithophaga), 8 cm long, California botula Botula (Adula) californiensis - up to 4 cm long; The gland that secretes this secret is located in front of the edge of the mantle; therefore they have a thin shell that is not involved in drilling. On the shores of the Mediterranean Sea, sea dates are valued as a tasty dish.

Very interesting shellfish from the tropical superfamilyBaptera(Pteriacea), whose shells have a well-developed mother-of-pearl layer, the anterior adductor muscle is very small or reduced, and the leg usually has a strongly developed byssus. This includes various pinnas and atrins, or feather shells(family Pinnidae), sea ​​hammers(Malleus, family Isognomonidae) and real sea pearls, or pterygoids(family Pteriidae). Pinns and atrins have a very characteristic wedge-shaped, often very large shell without hinge teeth and with a very strongly developed byssus. The surface of the shell is usually decorated with radial ribs or many scales.

The genera Pinna and Atrina include about 20 species living in the Mediterranean Sea, in the Atlantic, Pacific and Indian Oceans. noble pinna(Pinna nobilis), living in the Mediterranean Sea and in the Atlantic, reaches 30 cm in length, being the largest among the bivalve molluscs of the European seas. Inside the pinn shell of a beautiful reddish color, reddish or dark pearls are often found.

Byssus pinn, for which they are mainly mined, has the appearance of a dense bundle of thin silky threads of yellowish or brownish color. Its threads are elastic, very strong and have a beautiful sheen; in their composition there is a protein substance close to fibroin, which is part of silk. Pinnas and atrins live in shallow waters warm seas, attaching to solid ground or semi-submerging with a narrow end into the sand; in all cases, the wide end of the shell sticks out vertically upwards.

Products from byssus pinn were highly valued in previous centuries. Expensive fabrics and lace were made from it, distinguished by unusual brilliance and beauty. So, at the end of the XVIII century. in Italy, a pair of byssus pinn gloves cost 20 gold ducats.

Even more interesting are the species from the tropical Indo-Pacific genus Malleus. For the bizarre shape of the shell, they got the name "sea hammer". The hinge margin of the malleus shells is strongly elongated, while the valves of the thick calcareous shell are narrowed and elongated like a hammer handle. Inside the shells of M. malleus, M. albus and other species of this genus, pearls are sometimes also found, but less often than in ordinary pearl mussels.

Sea pearls have long been famous for the high quality of their mother-of-pearl and the ability to form the best and most valuable pearls. They are characterized by a large shell of various shapes, with a straight hinge edge, usually elongated behind into an ear-shaped or beak-shaped protrusion; the hinge margin with one or two tooth-like thickenings and the anterior adductor muscle are reduced, the byssus is strongly developed. The shell of pteria consists of two layers: an outer (prismatic) and a powerful inner (mother-of-pearl) layer. The largest of the pearl mussels, Pinctada margaritifera, can reach 30 cm in diameter and weigh 10 kg (they are usually smaller).

To sea ​​pearl oysters There are many tropical species, divided into two genera: pteria(Pteria, or Avicula) and pinctadas(Pinctada). The most commercially important are: Pinctada margaritifera, a shallow-water Indo-Pacific species also living off the coast of Central America and Australia, P. martensii off the coast of Japan; Ceylon pearl(R. vulgaris), etc. After the construction of the Suez Canal, the Ceylon pearl penetrated into the Mediterranean Sea.

Pinktadas and pteria lead a sedentary lifestyle, attaching themselves to underwater rocks and stones with their thick and strong byssus. Often they form banks - colonies and clusters at a depth of 5-6 to 60 m (usually at a depth of 10-15 m), living here together with other forms of epifauna, i.e. animals sitting on the surface of hard ground - corals , sponges, hydroids, etc. Pearl oysters do not tolerate desalination, being typical inhabitants of purely marine areas. They grow very slowly: at the age of three years, they reach a size of only 5-6 cm.

Even the same species of pearl oysters living in different regions of the ocean have great differences in size, shell thickness and in the quality of the mother-of-pearl layer, which determines their commercial value. So, the shell of Ceylon pearl oysters is usually 5-6.5 cm long and up to 8 cm high and has thin valves; the same species from the Persian Gulf are larger and thicker, and those from the Red Sea even larger. Here, the weight of their shell can reach 1 kg, and mother-of-pearl is of the highest quality.

The most important areas for the extraction of pearl mussels in the Pacific Ocean are the Zulu Sea, the Australian Great Barrier Reef, the Torres Strait, the coast of Panama and Japan; in Indian Ocean- Persian Gulf, Red Sea, coast of about. Ceylon and Madagascar; in the Atlantic, the Gulf of Mexico. The famous banks of pearl mussels have been fished for several hundred years. Fishing is carried out quite primitively - by local divers; diving suits and scuba gear are rarely used. Many banks of pearls at about. Ceylon is now already devastated, since they have been mined here for several centuries. The extraction of pearl mussels by swimmers diving without any equipment is a very difficult and even dangerous business, since a meeting with sharks is always possible. An experienced diver can stay underwater for 53-57 seconds; usually after a few years of such work, a person becomes deaf and becomes disabled, since he has to dive up to 30-40 times daily, collecting up to 2000 shells a day. In the Persian Gulf, up to 30,000 catchers work annually in the rich pearl fisheries. However, these banks here are located at a depth of up to 50 m, so the work of divers here is especially difficult. Diving operations require specially equipped Luger vessels and expensive equipment, which is unprofitable for entrepreneurs.

Since the predatory catch of pearl mussels undermined their stocks in many fishing areas, protective measures were introduced, and pearl mussels were artificially bred. Japanese zoologist Mitsukuri in Ago Bay for the first time created a farm for growing pearls. However, a more successful method for growing pearls in pinctads was proposed later and consisted in introducing pieces of mantle epithelium into the thickness of the mantle to form epithelial sacs. Having mastered this method, in Japan they learned to get about 50 thousand pearls a year, for which it is necessary to operate and keep about 1 million pearl mussels in special cages annually.

To group of single-skull(Monomyaria) from the order Dysodonta are three species-rich families of molluscs. This is first of all scallop family(Pectinidae), numbering many genera and species, widely distributed in almost all seas and oceans, at a wide variety of depths up to ultra-abyssal; Thus, in the Kuril-Kamchatka depression of the Pacific Ocean at a depth of 8100 m, the Vityaz found a large translucent Delectopecten, and this is still the greatest depth of occurrence of scallops.

The world of scallops is especially rich and diverse in the waters of coastal shallow waters of the subtropical and temperate zones of the World Ocean.

In the seas Soviet Union there are relatively few species of scallops, most of them live in the seas Far East. In the coastal shallow waters of the Sea of ​​Japan, to a depth of about 50 m, from Korea to Sakhalin and the South Kuril Islands, well-known Far Eastern scallops live: large (up to 20 cm in diameter, less often - more) seaside commercial scallop Pecten (Patinopecten) yessoensis, with a white radially ribbed shell, and very beautiful Swift's scallop- Chlamys (Swiftopecten) swifti. Also found in the southern part of the Sea of ​​Japan Japanese Farrera scallop(Chlamys farreri nipponensis).

In the Bering, Okhotsk Seas and in the southern part of the Chukchi Sea lives Bering scallop(Chlamys beringianus), as well as a number of other species from the genus Chlamys. The Bering scallop is most common at depths of 50 to 100 le, and is also found along the Pacific coast of America to California.

In the Far Eastern seas, and especially in the Barents and White Seas and in the southwestern part of the Kara Sea (where warmer waters penetrate from the west), a rather large (up to 8 cm in diameter) beautiful Icelandic scallop(Chlamys islandicus). It is also common off the coast of Iceland, Norway, South Greenland, off the Atlantic coast. North America. It occurs at depths up to 100 m and is part of some biocenoses of the benthic fauna. The meat of the Icelandic scallop is very tasty, but there is no fishing for it in our seas.

On soft silty bottoms of the Barents, Kara, Norwegian and Greenland seas at depths of more than 100 m, small species of scallops live propeamussiums, with a thin fragile shell. It's cold water Greenland scallop(Propeamussium groenlandicum) and scaly scallop(Pr. (Cyclopecten) imbriferum), living in the North Atlantic and in the southwest of the Barents Sea.

Only one lives in the Black Sea Black Sea scallop Chlamys (Flexopecten) glaber ponticus is a subspecies of the Mediterranean scallop. Its small (up to 5 cm) shell, brightly colored in yellow, pink and other colors, with a small number of ribs, is known to everyone who has been on the shores of the Black Sea. The Black Sea scallop lives at a depth of 50-60 m, mainly in the shell rock biocenosis, together with venuses, tapes, modioli and cockles.

Sea scallops have a rounded shell with a straight key (dorsal) edge, protruding on the sides in the form of angular protrusions - "ears". The upper valve is usually more flattened, while the lower one is more convex. The shell is decorated with radial or concentric ribs, often bearing spines or scales. At shallow-water scallops(Pecten, Chlamys) the shell is large, strong, variously colored in pink, white, lilac, reddish, often with a beautiful spotted pattern. Do more deep sea forms(Amussium, Propeamussium, Delectopecten) shell valves are fragile, thin, often translucent, with thin outer and sometimes inner ribs. There are no hinge teeth, but the ligament is well developed.

The closing muscle is large, fleshy, located in the middle of the shell; like in oysters, it is divided into two unequal sections: a large, anterior one consists of transversely striated muscle fibers and is capable of rapid vigorous contractions; the smaller, posterior part of the closure muscle is composed of smooth muscle fibers. The foot is small, digitiform, with a groove into which the byssal gland opens. In adult scallops, the leg is not used for locomotion. The gills consist of double unfused gill filaments, articulated in half. The edges of both lobes of the unfused mantle are thickened and slightly bent inward, forming the so-called "sail", which plays an important role in swimming scallops. The multi-colored mantle bears along the edge many thin sensitive outgrowths, at the base of which there are numerous small “mantle eyes”, which in living scallops glow with a beautiful greenish light. The number and arrangement of eyes in scallops is very different, but can reach a hundred; they are more numerous, and their number is greater on the upper half of the mantle. The eyes of a scallop can only "see" at a short distance. So, only when the greatest enemy of scallops, the starfish, comes close to him, the mollusk abruptly “turns to flight”.

The mantle eyes of scallops are quite complex: they are closed bubble-like formations sitting on small stalks. The eyes have a cornea, a light-refracting lens and a saucer-shaped (inverted) retina (retina), lined with two layers - the so-called "mirror" (tapetum), reflecting light (which determines the greenish luster of their eyes), and a pigmented layer. The ocelli are innervated by a nerve that runs around the mantle. In their origin, the mantle eyes of scallops differ from the head eyes of other mollusks, since their retina originated by protrusion of the outer (rather than inner) layer of the eye vesicle.

Almost all scallops can swim, moving in water in short jumps, while the shell valves first open and then quickly close again, the edges of the sail unfold and squeeze tightly, so that water is pushed out of the mantle cavity outward by two strong jets emerging in the area of ​​\u200b\u200bthe "ears" where the edges of the sail do not reach. The push thus obtained propels the shell above the ground with the ventral edge forward. The direction of the jump in this case is opposite to the direction of the water jets pushed out through the "lugs". The jump of a large scallop usually reaches a length of half a meter or even more. So he can swim a considerable distance.

In the movement of the scallops, an important role is played by its paired organs of balance - statocysts, located near the foot nerve ganglion. They are small closed vesicles lined inside with sensitive ciliary cells; inside these bubbles are calcareous formations (statoliths). The left statocyst is more developed and contains a larger statolith, while the right, smaller statocyst contains smaller calcareous grains (statoconia). In the usual position of the scallop - a convex valve down - the left statocyst is located at the top. If, during swimming, the mollusk accidentally falls to the bottom with its upper (flat) flap down, then it immediately flips over 180 ° with a push. The ability to move in this way allows shallow-water scallops to swim to deeper, cooler places during the hot season, and move closer to the coast in winter.

Scallops feed on detritus and various small planktonic organisms, extracting them from water sucked into the mantle cavity. One 4 cm comb can filter about 3 liters of water per hour, and a 7 cm comb can filter up to 25 liters of water per hour.

Scallops, like other mollusks, have many enemies, of which the most merciless are starfish and bottom octopuses: even their ability to swim does not always save scallops from them. In addition, scallop shells can be pierced with boring sponges; various algae, bryozoans, balanus (sea acorns) and other invertebrates can settle on them, making it difficult for scallops to move.

Of the large number of species of scallops, the inhabitants of the tropical seas are especially beautiful, the color of the shell and mantle of which comes in very different shades. Even in the Sea of ​​Japan, live scallops are very bright and beautiful.

The meat of scallops (more precisely, their large muscle-connector, and sometimes the mantle) has long been considered a tasty and tasty dish, and even the ancient Greeks and Romans always highly appreciated it. Currently, in almost all countries of the world, especially in coastal and island countries, scallops are eaten both fresh and frozen, canned and dried. Almost all types of large coastal scallops (pectens and chlamys) are hunted. Yes, in Atlantic Ocean are used: big scallop(Pecten maximus) scallop St. Jacob(P. jacobeus), scallop of Magellan P. (Placopecten) magellanicus and others.

In 1962, 1,160,000 q of sea scallops were caught, and they took third place in the world production of bivalve mollusks (after oysters and mussels).

Scallops are caught with dredges, nets, or are collected by divers. One diver in 6 hours of work can collect several thousand pieces.

The scallop fishery is developing successfully in the Soviet Union, and their freshly frozen or canned meat is widely sold. Our main production object in the Sea of ​​Japan is a large seaside scallop. The seaside scallop lives for a long time - up to 15-16 years, when it reaches a size of 18-20 cm, however, such old individuals are rare, usually scallops aged 7-9 years are found. Sexual maturity occurs in their third year of life (at a size of 9-10 cm), reproduction occurs in the summer (June - July). Five-, six-year-old females (12-13 cm) can spawn up to 30 million eggs. The plannton larva veliger rather soon settles to the bottom, turning into a young scallop (fry). In large numbers, fry live in coastal thickets of brown and crimson algae, either attaching to them with a byssus, or swimming, or crawling with the help of a leg (which is then reduced in adult scallops). By the end of autumn, the fry reach a size of 7-10 mm. The density of settlements of the seaside scallop off the coast of Southern Primorye reaches 7-10 specimens per 1 m2.

In Japan, scallop stocks are used so intensively that they have begun to artificially breed seaside scallops, although this is a very laborious and expensive undertaking. To do this, juvenile scallops are harvested from the sea after they have settled and transplanted onto bamboo sticks-collectors, with which they are then transferred for rearing to suitable areas of the seabed.

Close to the family of scallops discussed above are mollusks from spondylus families(Spondylidae) and lim(Limidae).

Limes have an elegant oval-ribbed shell; locking teeth are not developed, there is only one closing muscle. There are no mantle eyes, but there are sensitive outgrowths along the edge of the mantle, often very long and brightly colored. There is also a mantle sail, so limas can swim in leaps, just like scallops. Sometimes limas form a byssus, with the help of which some species, for example shining lima(Lima hians) can build "nests" by fastening pieces of shells, small pebbles, coral fragments, etc. with byssus. becomes comfortable bird's Nest. Apparently, the lima living in such a nest rarely leaves it, releasing only a thick mobile fringe of the edges of the mantle, which contribute to the creation of water currents for its nutrition and respiration.

However, many limas also lead a free lifestyle, such as small white northern limes- Lima (Limatula) hyperborea, living in the northern seas, or many more deep-sea species, found in the open parts of the seas and less often on the ocean floor.

Shellfish from Anomie families(Anomiidae) lead an attached lifestyle. Young anomia that have just settled on rocks and stones are firmly attached to them by the byssus, which is later impregnated with lime, turning into a hard stalk that emerges into a hole in the lower shell valve. No teeth; the shape of the shell is irregularly rounded, as it usually repeats the irregularities of the stones, to which it fits snugly. Anomia ephippium is common for the seas of the warm and temperate zones of the Atlantic, and in the Far Eastern seas giant anomie- Pododesmus (Monia) macrochisma, or Monia macrochisma. The size of the first is about 1-2 cm, and the second is up to 9-10 cm. Both live on stones and rocks of the coastal zone and shallow depths. A. ephippium is also found in the Mediterranean Sea, but does not penetrate into the Black Sea.

Close to anomies is a large tropical plakuna(Placuna placenta), which has an almost flat translucent shell 13-14 cm in diameter. She lives on rocky soils in the Indian and western Pacific Oceans. In India, China, on about. Celebes and in the Philippines, its shutters have long been used instead of glass in the windows of houses. Even now, in Manila alone, for these and other purposes, about 5 million pieces of plakuna are harvested annually; nowadays it is even bred here. Plakuna shells are also ground into a silvery powder, from which paint is prepared. Plakun meat is often eaten.

oysters(family Ostreidae) is one of the most popular commercial groups of bivalve mollusks that have been eaten by humans since time immemorial. This is evidenced by the presence of their shells in the so-called "kitchen heaps" - garbage left over from the ancient settlements of people who lived in the Stone Age on the shores of the seas (the Black Sea, the western part of the Baltic Sea, etc.). Mention of the oyster fishery is found by Pliny (that is, 150 years before the beginning of our chronology). All this suggests that the high taste and nutritional qualities of oysters have been known to people for a very long time. the question arose of the need for strict regulation of oyster fishing and their artificial breeding. In Japan, the culture of oysters originated in the 17th century.

Oysters have asymmetrical, coarsely scaly shells of variable shape; while the left one has a saucer-like shape, and the right one (flatter) covers it like a lid. With the left (lower) valve, the oyster adheres to stones or rocks, and often to the valves of other oysters or other sessile molluscs. The leg and byssus are completely reduced in adult oysters.

About 50 species of oysters are known. All of them are warm-water and do not penetrate to the north further than 66 ° N. sh. The main commercial species in different seas is common, or edible, oyster(Ostrea edulis), common off the coast of Europe - from Norway to Algeria and in the Mediterranean Sea, and it is absent in the Baltic Sea due to its low salinity. It has long been farmed and bred: for example, in France, oysters began to be bred in the seventies of the last century.

The true edible oyster is a highly variable species (as is the larger variety of oysters in general) and forms various local races and morphs, often considered even separate species, such as Adriatic oyster(O. e. adriatica), whose rich oysters have been known for a long time, rock oyster(O. e. sublamellosa) and our Black Sea bed oyster(O. e. taurica). Off the Atlantic coast of France, they also hunt Portuguese oyster(Crassostrea angulata).

In the Black Sea, oysters are found both in protected bays and on coastal rocks, and in shallow waters of more open parts of the sea, forming biocenoses of oyster ridges and banks in the shell rock zone. Large oyster banks near the Crimean and Caucasian coasts (for example, the Gudautskaya bank) are almost never used by the fishery. In addition, they suffered greatly from the eating of oysters and mussels by the predatory gastropod mollusc Rapana.

In the USA they hunt and breed: along the Atlantic coast virginian oyster(Crassostrea virginica), and in the Pacific - california oyster(Ostrea lurida).

Off the coast of Japan, there are several types of oysters, from which they are hunted and bred. giant oyster(Crassostrea gigas, or O. laperousi), Japanese oyster(Cr. nippona), leafy oyster(O. denselamellosa), etc. The giant oyster, common in the Sea of ​​Japan, is found off the coast of Primorye and Sakhalin, forming rich clusters - oysters, which are not yet used in our country. At the beginning of this century, this oyster was transported to the Pacific coast of the USA (Washington state), where it is widely traded.

The giant oyster is very variable in shape - from long, oblong to oval-shortened. Many other types of oysters are fished in Australia, New Zealand, India and many other countries.

Due to its great commercial importance and the need for artificial breeding, the structure and biology of the oyster are well studied in Japan, the USA and other countries, especially the early stages of its development. Artificially fertilized oyster eggs develop well and are grown in special pools (“tanks”); for their food is a small algae zoochlorella, also artificially cultivated.

Oysters usually live on hard soils - stones, rocks or mixed sandy-stony soils, at shallow depths, from 1 to 50-70 m. 300-400 m from the coast. Oyster banks are located in separate shallow waters, some distance from the coast.

Oysters are very sensitive to water temperature, especially during their breeding season, which occurs at temperatures around 18-20°C.

Oysters can tolerate some desalination. The minimum salinity at which they can exist is not lower than 12°/00 (1.2%).

The salinity of the water affects the growth of oysters and their taste. The fattest and tastiest oysters are harvested at salinities between 20 and 30°/00 (2-3%), where there is little desalination from river waters. At high sea salinity (up to 3.5%), they grow well, but their meat becomes tough and unpleasant in taste; at even higher salinity (about 3.7%), oyster growth slows down. These properties were well known even to the ancient Romans, who kept oysters collected from the sea in small desalinated reservoirs. It was noted that the most delicious oysters were mined only where there was an influx of fresh water.

With an open mantle and gills, oysters are very sensitive to the purity of the water and to the sufficient amount of oxygen in it for breathing. Therefore, the death of whole oyster jars is often observed when they are carried in with silt and sand after storms; silt clogs the gills of oysters and makes it impossible for them to filter the water necessary for nutrition and respiration.

On banks, oysters sometimes live very densely, then their shells stand vertically, with the ventral edge up; often oysters live on top of each other, in several tiers, forming huge intergrowths - “brushes”. In places, their average number is about 20-50 pieces per 1 m2 of bottom area. In addition, they can also live as single specimens.

Almost all oysters (Ostrea) are hermaphrodites, the male and female lobes of the gonads are mixed in them, and sometimes the same lobule produces eggs and sperm. The possibility of self-fertilization is excluded because different reproductive products mature at different times. In the same individual, sex may change periodically.

Fertilized eggs stay in the mantle cavity of the mother for some time, and already formed larvae enter the water. The number of eggs laid by an ordinary oyster varies from 300 thousand to 6 million. The larva of the sailboat (veliger), about 0.2 mm in size, already has a small bivalve shell. Settling, the larva chooses a suitable soil for itself, to which it attaches first with the help of the byssus, and then with the entire shell. Commercial species of Crassostrea are dioecious; hermaphroditic individuals are extremely rare. Fertilization is external. As mentioned above, the culture of oysters is currently very widely developed.

The development and application of the basic methods of growing oysters belongs to France, namely Cote, to whom France owes the existence and development of the modern oyster industry.

The first task that had to be solved for breeding oysters was the collection of oyster fry, the so-called spat, and transplanting them onto collectors that are placed on oyster banks during the breeding season of oysters. For this, fascines (bundles of rods), tiles or other materials were first used. In Japan, bamboo stems are used. Spat collectors stay in the water for a year until the juveniles grow up. In the spring, the spat is removed from the collectors and transferred to special boxes - receptacles for feeding. The receivers are kept in "oyster parks", that is, in special fenced areas of the seabed. Here they are kept for about two years, then they are sold to oyster plants for fattening. Here they live in small artificial pools, "clairs", up to 4-5 years, after which they can be sold. The water in these pools is usually fertilized with mineral salts, which leads to the rapid development of unicellular algae, which feed on oysters. One individual of the Virginian oyster can normally filter from 5 to 16 liters of water per hour. Before selling, oysters are transferred to special "cleansing" pools, where they are kept without food for several days in clean fresh water, after which they are washed with brushes and the water is drained. Now they are ready for packaging.