The pearl oyster is a hermaphrodite. Family: Margaritiferidae = Freshwater pearl mussels. Who are hermaphrodites from a legal point of view

Description

Large bivalve mollusk (shell length up to 160 mm). Outside, the shell is dark brown or black (yellow-green in young specimens), usually elongated, oval-quadrangular, slightly convex. The tops almost do not protrude.

The shell near the umbo is usually severely eroded and the periostracum is completely destroyed; the umbo sculpture is visible only in the youngest specimens. Inside the valves, on their dorsal margin, there is a lock consisting only of cardinal anterior teeth.

At the right valve, the tooth has the shape of a high irregular quadrangular pyramid and is placed under the umbo, slightly in front of it. There are 2 cardinal teeth in the left valve, less pronounced and separated by a gentle depression. The ventral margin of the valve is usually straight or slightly concave. The mother-of-pearl layer is thick, white with a pinkish tinge, often with green spots.

Spreading

Rivers of the Atlantic coast north-east. USA, east Canada, app. Europe, the Baltics, Belarus and the forest zone of the north-west. Russia. On the territory of Russia, it is known from Karelia, Murmansk, Leningrad and Arkhangelsk regions. The original range of the species, apparently, covered the bass rivers. White, Barents and Baltic seas. Now the range has been drastically reduced.

Habitat

The fertility of one female is 2-6 million glochidia. They reach the gills of the fish passively with the flow of water, become covered by the epithelial cells of the fish and develop into juvenile mollusks within 10-11 months. No significant harm to fish has been noted. Juvenile mollusks fall out of the gills of fish in the summer. Sexual maturity at the age of 10-20 years.

The ability to spawn is maintained throughout life. Live up to 130 years. The highest mortality at the stage of glochidia (99.99%) and juveniles up to 5 years (95%). The main causes of natural death in the spring are ice drift, in the summer - eating by predators.

population

All in. America and zap. Europe, the number now does not exceed several million individuals. In the XX century. population has declined by more than 90%. The largest populations remained in Russia: in the rivers of the Murmansk region. (about 150 million individuals) and Karelia (about 42 million individuals). The density of mollusks is up to 200 ind./m2 of the river bottom.

In most rivers, the density is lower (less than 12 ind./m2). The rapid decline in the number of mollusks, and in some places their complete disappearance, is caused by poaching and industrial fishing of mollusks, deforestation, fertilization, pesticides, timber rafting, water pollution by industrial effluents, acid rain, reclamation works in the riverbed, eurofication, as well as factors that reduce the number of fish -hosts (overfishing, construction of dams, acclimatization of other fish species, etc.).

The number of mollusks and their distribution are also affected by the degree of mineralization, the chemical composition and oxygen saturation of water, the speed of the current, the nature of the soil, temperature, and the presence of a sufficient density of host fish.

Security

Listed on the IUCN-96 Red List, European Red List, Appendix 3 of the Berne Convention. In the Kandalaksha and Lapland reserves, in the National Park "Panajärvi" there are small stream populations of pearl mussel. At the end of the 80s. attempts were made to reacclimatize mollusks in some rivers sowing.

Russia, methods have been developed to intensify reproduction in natural reservoirs and on the basis of salmon farms. It is necessary to reduce the likelihood of eutrophication and pollution through strict control and monitoring of water quality, the creation of protected areas in unpolluted basins. (especially important - in the last remaining large renewable populations of the Varzuga and Umba rivers on the Kola Peninsula and the Keret River in Karelia), limiting industrial and reclamation work in the habitats of pearl mussels, restoring their populations using developed methods, preventing the acclimatization of salmon fish, not serving as hosts of pearl mussels, international coordination of work in the field of research on ways to restore populations of pearl mussels and environmental legislation, breeding of molluscs in specialized farms.

Sources: Zhadin, 1938; 2. Zyuganov et al., 1993; 3. Ziuganov et al., 1994; 4. Young, Williams, 1984; 5. Bauer, 1989; 6 Woodward, 1994; 7. Zyuganov et al., 1988; 8. Zyuganov et al., 1990; 9. Zyuganov et al., 1991.

Compiled by: V.V. Zyuganov, A.A. Zotin

Bivalves (Bivalvia)

The most common molluscs from among the large representatives of the class of bivalves (Bivalvia) in our fresh water bodies include members of the family Unionidae (perlovitsa) - river nerlovitsa (Unio) and toothless (Anodonta); pearl oyster (Margaritana) is found in the north, northwest and the Far East, not often (Zhadin).

In ordinary fishing with a net from the shore, barley and toothless are rarely caught; the best way to get them is when swimming or from a boat, sat down with a net with a strong rim to rake the bottom soil, along which these mollusks crawl, half buried in the sand and leaving long groove-like tracks behind them, clearly visible on the shallows. In a pulled shell, both shell valves are tightly compressed. In this position, you can only get acquainted with the outer surface of the shell; in order to see its inner surface, it is useful to put an empty shell of shells next to it, of which there are always many on the sandy bank of the river; for inspection, you should choose one in which both shell valves have not yet disintegrated.

From the outer surface of the shell, we notice a protruding somewhat elevated part - this is its oldest part or top; the edge on which the top is located is called the upper edge of the shell, and the one opposite to it is called the lower one. The wider end of the shell represents its anterior margin, and the narrower, somewhat elongated and distant from the apex, posterior margin. Behind the apex there is an elastic plate or ligament, with the help of which both shell valves are connected to each other. The upper surface of each shell valve is concentrically striated; some of the arches protrude more sharply than others, stretch along the entire length of the shell and have a somewhat wrinkled appearance; these are the annual arcs corresponding to the winter pauses in shell growth, from which, with some approximation, the age of the shell can be determined. From above, the shell is formed by a greenish-brown or brownish stratum corneum, bearing streaks of growth, and from below, by a shiny smooth mother-of-pearl layer; when broken, it can be seen that between the horny and mother-of-pearl layers lies a matte-white porcelain layer. A microscopic examination of the transverse sections of the shell showed that the porcelain layer consisted of calcareous prisms closely lying one on top of the other in a direction perpendicular to the shell surface; the mother-of-pearl layer consists of many thin, also calcareous layers, lying on top of each other. They refract and reflect the light falling on them, which is why the inner surface of the shell is cast in various colors or, as they say differently, iridescent. The mother-of-pearl tint changes depending on which side and at what angle, when viewing the shell, the light falls on it. Calcium carbonate makes up 98% of the shell.

Sometimes, under the influence of some mechanical action, the outer horny layer of the shell is destroyed, revealing the underlying prismatic layer, which is easily dissolved in soft waters rich in free carbon dioxide, and mollusk shells in such waters are corroded (for more details, see Zhadin, 1933, p. 39).

On the inner surface of the shell (IV, 1), its thickened upper edge or hinge plate is visible. It is called so because it carries outgrowths or teeth that enter the recesses of the opposite plate, forming the so-called "castle"; the teeth in front of the litament are short and massive, those behind it are elongated and thin. So fully the castle is expressed in pearl barley; in the pearl oyster, some teeth are reduced, and in the toothless, they are completely absent, which is why its name comes from. At the anterior and: at the posterior ends of the inner surface of the shell there are spots formed by irregularities in the mother-of-pearl layer at the points of attachment of the shell closing muscles; by the force of contraction of these rather powerful muscles, the shell valves are tightly compressed one with the other, and if the shell is pulled out of the water, its body retains the necessary supply of moisture for some time. The action of the shell-opening ligament is best observed in dead animals; under the influence of contraction of the ligament, the shell valves open a little, which is noticeably good on the shells freed from their contents.

According to the shape and structure of the shell, three eye genera of our large shells can be distinguished. In addition to a pronounced difference in the structure of the teeth and the locking apparatus, barley (Unio) are distinguished by an elongated hard-walled shell with a prominent apex close to the anterior end (V, 3); the shell of the toothless (Anodonta) is broadly oval, thin-walled, its apex is slightly protruding, the keel of the upper margin is high in some species (V, 5). The shell of the pearl oyster (Margaritana) is large, elongated, thick-walled, with an almost straight or even slightly concave lower edge; upper margin partly nearly parallel to lower margin (VI, 1).

It is most convenient to begin acquaintance with the structure of the soft body of a shell with observations of a living mollusk. To do this, place the shell in an aquarium with a sandy bottom or just in a basin of water and sand and let it calm down. At first, the shell lies motionless on its side. Then the valves of its shell slightly open and from the front edge of the gap formed, a tongue-shaped fleshy organ - the leg of the shell - begins to gradually, very slowly protrude; little by little the leg lengthens, takes on a wedge shape and sinks into the sand (IV, 2). After that, the body of the mollusk acquires a vertical position and burrows its slightly forward end into the sand; after that, the shell begins to move slowly, leaving behind a characteristic mark on the sandy bottom in the form of a shallow furrow. If snails are not fast in their movements, then toothless and barley are even slower. They launch their wedge-shaped leg with the front end into the ground and then pull themselves up to it with their whole body. Pushing the leg forward depends on the rush of blood to it, and retracting it is done by contraction of the muscles attached to the wall of the shell; the places of attachment of the leg muscles can be seen on the inner surface of the shell next to the imprints of the muscles of the contactors. The physicist and famous naturalist Réaumur figuratively compares these mollusks with a man lying on the ground, who grabs an object with his hands and is attracted to it with his whole body, without using his legs at all. The river barley takes only 5 steps in 4 minutes, each time barely moving 2-3 centimeters. She, like the toothless, is out of the question about climbing vertical surfaces.

At the time when the shell slowly crawls along the bottom or sits motionless, burrowing its front edge into the sand and protruding its rear, the valves of its shell are somewhat ajar (IV, 2.3). Carefully peering with a hand magnifying glass into the gap formed by the shell valves, one can see the mantle lobes, closed at the edges; posteriorly, the edges of the mantle are weakly cut in two places and somewhat elongated in the form of ajar, adjoining lips, forming openings or siphons, the upper smaller one is outgoing and the lower one is large - adductor (IV, 2, 3). The edges of the first are thickened and smooth. The edges of the latter are pigmented, seated with small finger-shaped papillae. One has only to touch one of the papillae with a needle or straw, as the siphonal opening closes, the edge of the mantle retracts, and after that the shell valves begin to close due to the contraction of the closing muscles. If you add crushed carcass to the water so that it gets near the crack of the shell, you can see how the water with carcass particles is drawn into the lower, leading siphon; after a while, it is seen how the ink is thrown out along with the flow of water from the upper, leading out siphon; the ejected jet is quite strong, and the particles of the carcass are at a considerable distance.

In order to continue acquaintance with the structure of the soft body of the shell, it is necessary to open the shell by cutting the closures that compress it. It is more convenient to do this on a fixed material. "The shell is taken in the left hand with the front end up, a scalpel is inserted between the valves, with which the anterior closing muscle is cut (IV, 4). Then the shell is turned upwards with the back end, with the ligament out. By inserting the scalpel from the back, the rear closing muscle is cut" ( Zhadin). After removing the shell, one can see the skin of the mollusk, its mantle, symmetrically lining each side of the shell valve, formed in the process of growth by secretions of the outer wall of the mantle. The lower folds of the mantle are attached to the shell by a series of thin muscles, the imprints of which leave a mark on the shell, called the mantle line (IV, 1). The cavity formed by the closing of the outer edges of the mantle lobes is called the mantle cavity, gill or respiratory space (IV, 5). In the middle of this cavity is a muscular leg of a mollusk, and on both sides of it hangs a pair of lamellar gills. The mouth opening opens in front above the leg; on the sides of it are the oral lobes of the shell, which are small paired triangular plates. The gills of opposite pairs behind the leg are partly fused with each other; the slit remaining in front of this gill commissure leads to the supragillary space or cloacal cavity located above (IV, 7), into which the anus of the shell also opens. The cloacal cavity opens outwards with a small dorsal opening; and a wide rear, that is, an outflow siphon, which was mentioned above (IV, 2, 3, 7). The surface of the leg, gills, and inner walls of the mantle is lined with ciliated epithelium (IV, 6, 8).

Each gill is a double-bent plate, consisting of many threads adjacent to each other, connected like a lattice. Through the slits of the gills, water is filtered into the intragillary cavity, and from there it enters the cloacal cavity and through the outward siphon: the gills are continuously washed by a current of fresh water (IV, 7). With such filtration, substances suspended in water are retained on the gill lattice; what is suitable for food is clothed with mucus, and food particles are driven in lumps to the mouth opening by the work of ciliated cilia of the epithelium of the gills; as food accumulates at the mouth opening, it is swallowed by mollusks. For some reason, unused residues are pushed into the cloacal cavity and removed outward along with feces and filtered water. Water can be ejected with force from the gap of the cloacal cavity: in a river shell 7.5 cm long, water is ejected from the shell in a jet up to 40 cm long.

Living at the bottom of the reservoir semi-submerged in the ground, living due to suspensions above the underlying water column, slow shells, thanks to the incessant activity of the cilia of the ciliated epithelium, are the most energetic filter feeders: one large shell passes 1 liter of water through its mantle cavity with lattice gills for 40 minutes, which is about 40 liters of water per day - a significant amount, if we take into account the huge number of shells that live in our reservoirs, and the continuity of their filtration activity. Shells play a big role in the conversion of silts; releasing a huge amount of mucus, they bind and compact the silts.

A peculiar way of life in conditions of low mobility with vigorous washing of their delicate body by a stream of water creates specific features of the physiology and morphology of laminabranch molluscs. Being inhabitants of the bottom zone, where organisms with moderate oxygen requirements usually live, large shells, in particular: Unio, are rather highly oxyphilic organisms, and the oxygen regime in the water bodies inhabited by them should be free from winter and summer deficiencies. Morphologically, they represent forms on which the uniqueness of the situation has left a sharp imprint: they have no eyes, no real tentacles, no pharynx, no food-crushing organs, no copulatory organs. The amount of sexual products thrown out, with the uncertainty of their future fate, is enormous. The development and distribution of offspring in shells is biocenotically associated with organisms leading a mobile life, namely with fish.

Each mature glochidium is a small bivalve mollusk, the shell valves of which open wide and slam shut quickly and easily due to the contraction of a highly developed locking muscle. The lower edges of the shell are equipped with sharp teeth, and a long sticky thread of byssus extends from the negligible leg of the larva (V, 1). Leaving the cavity of the gills and the body of the mother, glochidia fall to the bottom, where they lie, from time to time slamming the valves of their triangular shell; when the shell closes, they float up from the bottom. If some fish swims close, for example, a perch, then the byssus sticks to its mucous skin, the shell valves slam shut and dig their teeth into the skin of the fish; thus, the glochidium is firmly attached to the surface of the body of its temporary host. Soon, the glochidium becomes skinned or, as they say, encysted. Being a foreign body for the fish organism, glochidia causes inflammation of the surrounding tissues of the host. During their life on it, glochidia feed on the tissues and juices of the host and complete their development; in May - June or July, young mollusks leave the skin of the fish, fall to the bottom of the reservoir and switch to a free lifestyle.

It is interesting to note that the shells themselves provide shelter for the development of juveniles of a small fish - mustard Rhodeus sericeus (= R. amarus, V, 2) with a body length of about 6-7 cm. The female bitterling lays eggs in the mantle cavity of large bivalve mollusks Unio and Anodonta. Before the start of spawning, the females begin to grow an ovipositor, reaching 5-7 cm in length and hanging down in the form of a reddish tube. As the ovipositor grows, it fills with eggs. When the filling is completed, the female bitterling introduces the ovipositor into the slit of the shell, which serves for the passage of water, and lays eggs in the gill cavity of the mollusk ( The length of the ovipositor, according to Berg, may exceed the length of the fish). Here they are fertilized by the live bait of the male. Under the protection of a closed shell, bitterling eggs develop in safety; fry hatch from them, which also spend the first time of their life under the roof of the shell; upon reaching a certain age, young fish come out and begin an independent lifestyle.

The behavior of the mustard and mollusks during the mating season of this fish is extremely colorfully described by Zolotnitsky from observations in the aquarium. "During spawning, the male takes on an iridescent color: his back becomes greenish-brown, his gills and sides are cast with pink mother-of-pearl, the side stripe becomes bright blue, and the anal fin becomes crimson-red. During laying, the female releases a reddish-orange ovipositor, which, hanging from her behind the anus, gives the fish an extremely original look. Having planted mollusks in an aquarium with mustards, Zolotnitsky describes the behavior of the fish as follows: “As soon as the mustards noticed the presence of Unio in the aquarium, they immediately sounded the strongest alarm: swimming around the shells, they touched them, then moved away, chased each other and again The next morning, the female's ovipositor, usually in the form of a small hook, barely noticeable, in one night extended so that it went behind the caudal fin and, when the female descended, dragged along the bottom.The male at this time was in alarm, chasing the female without leaving her for a moment. Approaching the sink, he began to tremble violently." The actual laying of eggs is carried out as follows: “A thickening appears in the female near the end of the ovipositor, and in it an egg has the shape of a small rice grain. The female swam from one shell to another, the male followed her, or, ahead of her, examined the shell himself. Approaching the shell, the female began to swing her ovipositor with the eggs clearly visible in it from side to side, just as she swings the layers with her trunk, and, pressing the ovipositor under her, tried from time to time to lower it into the hole in the shell's mantle. These maneuvers lasted for minutes ten. Finally, having probably found the position of the shell convenient, the female hit her abdomen hard and, quickly bending the tube of the ovipositor under herself, lowered it all into the shell. The male immediately rushed after the female to release milk into the shells.

Such an amazing adaptation of the mustard to reproduction is due to the small number of eggs it lays. If they developed in the usual way in water, they would become the prey of predatory inhabitants of reservoirs and could be completely exterminated, which would lead to the extinction of mustards. Laying eggs inside the shell of toothless or barley is an excellent way to give reliable protection to your few offspring. A constant flow of water through the shell brings the necessary oxygen for the development of eggs and food for fry. At this time of its existence, the mustard is closely related to mollusks; the fish is, as it were, a tenant of the mollusk and, moreover, one that does not bring any harm to its owner. This ratio of two animals is cohabitation; more precisely, bitterness is a cohabitant of a mollusk. Gorchak, for its part, can be useful for shells, bearing its glochidia on its skin.

Perlovitsy(Unio) are widely distributed in our fresh waters. The most common are two types: pearl barley(Unio pictorum, V, 3) and wedge-shaped barley(Unio tumidus, V, 4); both species prefer flowing water, but are also found in lakes and large ponds if the water in them has a sufficient amount of oxygen. The length of the shell of the named species of barley varies between 6-10 cm. The third type is barley oval(Unio crassus) is less common than the first two, moreover, only in rivers and under the condition of a somewhat greater speed of flow than the first two species. Glochidia Unio pictorum are the largest among pearlworts. In large rivers, like the Volga, Kama, Oka, common barley (Unio pictorum) keeps in the coastal region on sandy, sandy-silty and clay-sandy bottoms, but prevails in channels, branches and zakosyas, where the current is slow, and the soil is more silty , The wedge-shaped barley (Zhadin) lives in the same conditions.

Kinds toothless(Anodonta) are extremely variable and form numerous varieties. Anodonta piscinalis (V, 5) occurs in rivers, but is not as characteristic of them as Unio species. Anodonta piscinalis var. lives in the Volga. volgensis Shad.; the length of its shell is 6-14 cm. Anodonta anatina lives in rivers and lakes, including the Neva and Lake Ladoga; its shell is 6-8 cm long. Anodonta cygnea (V, 6) and variable Anodonta cellensis live in stagnant water; they predominate in lakes, river oxbow lakes and ponds, and the lake-pond Anodonta cygnea sometimes gives gigantic forms, reaching 20 cm in length; the usual sizes of the two named species are 9-16 cm.

Common pearl oyster(Margaritana margaritifera) is distinguished by its massive thick-walled elongated shell, the tops of which are usually eaten away (VI, 1). The mother-of-pearl layer is brilliant white. If any foreign body, for example, a grain of sand, gets between the shell valve and the mantle of the mollusk adjacent to it, then it has an irritating effect on the animal, and the skin of the mantle begins to secrete a hardening mother-of-pearl substance that encircles the foreign body on all sides (VI, 2 ); in the end, a pearl is formed (VI, 3), which, therefore, in a mollusk is a formation of painful origin. River pearls are valued much lower than sea pearls.

These are our large laminabranchs, belonging to the Perlovitsa family (Unionidae); they live in lakes and rivers, and their extraction is sometimes associated with difficulties.

It is much easier to find small laminabranchs belonging to the globular family (Sphaeriidae). These small bivalves are caught in a water net. almost every excursion to a pond, lake or river with thickets or a silty bottom. They belong to the genera Sphaerium, peas (Pisidium) and muscles (Musculium = Galyculina); their sizes do not exceed 20-25 mm, and for peas 10-11 mm. The named genera are easily distinguished by the position and shape of their shell tips: in the pea (Pisidium), the tip is more or less displaced from the middle of the shell to its posterior end (VI, 5); in the spherule (Sphaerium) and muscle (Musculium), the apex is located in the middle, and in the spherule it is widely rounded, slightly protruding (VI, 4), and in the muscle it is narrow, papillary, strongly protruding above the upper edge (VI, 7); the shells of large species of ballfish are 15-20 mm long, while the shells of peas usually do not reach 10 mm. The shell of Sphaeriidae is thin, delicately striated, its mother-of-pearl layer does not irritate, and the imprints of the closing muscles are weak.

Sharovka horny(Sphaerium corpeum, VI, 4) lives among thickets, and this mollusk can crawl along the surface of plants, holding on to them with the help of mucus secreted by its foot; Sharovka can burrow into silty or sandy soil, but not deep. The lobes of the mantle in Sphaeriidae are fused at their outer edges, except for the leg openings and two siphons. When the mollusk is calm and puts forward a leg from the half-open shell in front, at the same time at the posterior end of the body it puts out tender, contractile translucent tubes, of which the lower one is the incoming siphon, and the upper one is the outgoing one. The outer gill is smaller than the inner gill.

Like all Sphaeriidae, the horny hermaphrodite. Fertilized eggs are hatched in a special space intended for this on the inside of the gill sheets, where the embryos; undergo all their development, and small mollusks that have reached a significant size and already sexually mature come out of the mother's shell; their number, especially in young individuals, is small, and the sizes are relatively large - sometimes they reach 1/5 of the size of the mother's organism.

Sharovka river(Sphaerium rivicola) is the largest of the Sphaeriidae; the length of its shell reaches 20, and sometimes 25 mm. Lives in rivers and river backwaters on a silty and silty bottom.

The pea genus (Pisidium) is rich in species that are difficult to distinguish from one another; they are the smallest of the bivalves. On fig. 6 tab. VI shows a pea with an open shell and a removed left fold of the mantle; at the same time, one can see how the shortening of the posterior half of the body is reflected in the arrangement of organs. The outer gill of the pea is much larger than the inner one (on VI, 6 it is turned to the side). The internal gill has the form of a triangle, its longitudinal axis is directed almost vertically to the longitudinal axis of the shell, and the gill filaments extend almost parallel to it. The leg is narrow. The closing muscles are close to the edges of the animal's body. Juveniles hatch on the gills and reach a considerable size.

One of the largest types of peas is river pea(Pisidium amnicum) with a shell length reaching 10-11 mm: (VI, 5), this mollusk is often found on the silty-sandy bottom near the banks of rivers and backwaters. The silty and silty bottom of the lakes is inhabited by numerous species of peas; among them is a small Pisidium conventus with a shell length of 2.5 mm, which lives in cold-water and clean lakes, descends to a considerable depth, over 100 m.

Peas Pisidium obtusale (shell length 3.5 mm, VI, c) and Pisidium casertanum (shell length 4 mm) live at the bottom of the smallest reservoirs, and they can endure their temporary drying, burrowing into the ground, tightly closing the valves of their small shell and thus keeping your body moist.

Pond muscle(Musculium lacustre) is distinguished by an unusually delicate, thin-walled shell with a swollen top; shell valves slightly convex and narrow in cross section. This species is characteristic of small overgrown and swampy water bodies (VI, 7); shell length 7.5 mm.

A very special position among the lamellar gills of our fresh waters is occupied by Dreissena(Dreissena polymorpha), belonging to the family Dreissenidae. This mollusk retained the greatest similarity with marine forms, in particular with mussels. The surface of the shell is greenish with transverse zigzag dark stripes; shell length 30-40 mm. The edges of the mantle are fused, with the exception of leg slits and short siphon tubes.

Dreissena chooses a wide variety of objects as a place of attachment: its byssus adheres equally well to a stone, to a wet tree, to a Unio or Anodonta shell, where zebra mussels are usually located near the posterior edge of the shell (VI, 9). Dreissena is also strengthened on the bottoms of boats, barges, steamers or on driftwood, thus undertaking sometimes the most distant journeys.

Dreissena is native to the Ponto-Caspian basin. Here it was first found by Pallas in the Ural River in 1769, and then by other researchers in the Volga basin; in the Dnieper, Dreissena polymorpha was discovered by Kessler in 1844. Moving upstream, dreiosena widely settled in the river basins of the Caspian and Black Seas, and with the development of navigation and, in particular, with the digging of connecting channels, it penetrated into the Baltic Sea basin and populated the lakes and rivers of the western Europe, where it spread to England. As the presence of zebra mussel in completely closed water bodies shows, this mollusk can overcome watersheds even without the mediation of channels, settling with the help of dragged boats and fishing equipment (Ovchinnikov).

Once settling in a reservoir, Dreissena develops in masses in it, which can cause great harm, hindering the movement of ships and interfering with the operation of hydroelectric stations. At the Dneproges, this mollusk develops abundantly on the gratings of pressure pipes and on the shields of hydroelectric stations, and sometimes even penetrates into the water supply of the station (Zhuravel). Periodic cleaning of the structures is of little help, as Dreissena soon breeds again. The invention of an agent that has a destructive effect on the byssus or on the whole mollusk is an important economic problem, the solution of which is being worked on by a number of researchers.

Sleeping Hermaphrodite (Sleeping Hermaphroditus): Sculptor: Gian Lorenzo Bernini, date 1620, Material marble, Size 169 cm

The sleeping Hermaphrodite has been described as a good Roman copy of a bronze original by the later of two Hellenistic sculptors named Polycles (155 BC); the original bronze specimen was mentioned in Pliny's Natural History.

The Sleeping Hermaphrodite is an ancient marble sculpture depicting a life-size Hermaphrodite reclining on a mattress by sculptor and Italian artist Giovanni Lorenzo Bernini in 1620. The form comes partly from ancient depictions of Venus and other nude women, and partly from contemporary Hellenistic depictions of Dionysus/Bacchus. Sculpture is a subject that was much repeated during the Hellenistic era and in ancient Rome, judging by the number of versions that have survived. Discovered in the early seventeenth century, the Sleeping Hermaphrodite became part of the Borghese collection and was later sold to the Louvre in Paris, where it is today.

The subject of the image is not something obscene. The sculptor depicted the son of Hermes and Aphrodite, who united with the nymph Salmacis, took her forms, but became a dual male creature, but with the breasts and forms of a woman. The sculptor found a theme expressing the Greek style: relaxed nudity, the effect of surprise and theatricality were combined centuries later in the art of the Italian Baroque, illustrated here by Bernini, who depicted sensual courtesans, compared with whom Greek statues look completely innocent.

Original copy of Borghese

The ancient sculpture was discovered in the first decades of the seventeenth century, it was excavated in the territory of Santa Maria della Vittoria, near the baths of Diocletian and within the gardens of Sallust. The discovery was made either when the church foundations were in the ground (in 1608) or when the trellises were planted.

The sculpture was presented to a connoisseur, Cardinal Scipio Borghese, who in turn bestowed an order on the services of his architect Giovanni Battista Soria and paid for the façade of the church, albeit sixteen years later. In her new Villa Borghese, a room called the Hermaphrodite Room was dedicated to her.

In 1620, Gian Lorenzo Bernini, Scipio's protégé, was paid sixty scudis to adopt a mattress on which Hermaphrodite reclined, so strikingly realistic that visitors are inclined to give it a test.

The sculpture was purchased in 1807, with many other pieces from the Borghese collection, from Principe Camillo Borghese, who married Pauline Bonaparte, and was transferred to the Louvre, where it inspired Algernon Charles Swinburne's poem "Hermaphrodite" in 1863.

Ancient copies

A 2nd century copy of the Sleeping Hermaphrodite was found in 1781. A third Roman marble variant was discovered in 1880, during construction work to make Rome the capital of a newly unified Italy. Currently on display at the Museo Palazzo Massimo Alle Terme, part of the National Museum of Rome.

Additional ancient copies can be found at the Uffizi in Florence, the Vatican Museums in the Vatican, and the Hermitage Museum in St. Petersburg.

Modern copies

Many copies have been produced since the Renaissance, in various media. A full-size copy has been issued for Philip IV of Spain in bronze, (ordered by Velázquez) and now in the Prado Museum, and in Versailles (sculptor Martin Carlier, in marble). The composition is clearly influenced by Velazquez's painting of Rokeby Venus, now in London. A smaller scale bronze copy, compiled and signed by Giovanni Francesco Susini, is in the Metropolitan Museum of Art. Another smaller copy scale, this one produced in ivory by François Duquesnoy, was bought in Rome by John Evelyn in the 1640s. American artist Barry X Ball presented a life-size replica compared to the Louvre version, made of Belgian black marble on a Carrara marble base, which was completed in 2010.

Story

He was raised by naiads on Mount Ida in Phrygia. Once, on the shore of the lake, he met the beautiful nymph Salmakida, who fell in love with the young man at first sight and offered him to become his bride. The young man, who knew nothing about love, in fear rejected the love of the nymph. When Hermaphrodite decided to bathe, the nymph followed him into the water and embraced the young man. The gods, heeding the prayers of Salmakida, forever connected the body of the girl with the body of her lover, and Hermaphrodite emerged from the lake, becoming both a man and a woman. At his request, Aphrodite and Hermes made the lake magical and since then everyone who enters its waters becomes the same as Hermaphrodite. In memory of the love of the nymph, the lake was called Salmakida.

Cult center. The cult was popular in Attica at the beginning of the 4th century. BC.

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 filaments 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 (the remains of aquatic plants and animals), as well as unicellular 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 settlements of mussels 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 ones 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 also take part in the formation of silty soils with their pseudofeces and feces. Mussels usually feed all year round, but less intensively 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 sturgeons. But their constant enemy, usually living in the areas of mussel settlements, are large starfish that feed on them, as, for example, in the Atlantic - Asterias rubens, and in the Far Eastern seas - A. amurensis, Patiria pectinifera, etc. One star eats every day in 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 tolerate significant temperature fluctuations: in the summer in the littoral zone at low tide, it can be very warm by the sun, and in winter, in the harsh conditions of the White and Barents Seas, mussels can even freeze, 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.

The annual world production of mussels (mainly edible) has increased in recent years 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.

In view of the fact that in many countries the natural stocks of mussels are significantly undermined and threatened with extinction, as in France, for example, 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 accidentally, perhaps on the bottoms of wooden ships transported by land from the Azov to the Caspian Sea, was brought here, where he found very favorable conditions for existence (both in terms of salinity - 10-12 ° / 00, and food), quickly multiplied and spread widely. 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 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 the shallow waters of warm seas, attaching themselves to solid ground or half-submerging their 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 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 the Indian Ocean - the Persian Gulf, the Red Sea, the 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 of the Soviet Union, there are relatively few species of scallops, the largest number of them live in the seas of the 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 of 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 the 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 drilling 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. So, in the 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, but usually scallops are found at the age of 7-9 years. 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 settle 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 like a cozy 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 mollusks. 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 accumulations - 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 on 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 young oysters, 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.

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 in a woman's way, and during the pilgrimage they must wear women's clothes. 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 - both in the plant world (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, annelids 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, however, 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), an individual sequentially produces male or female gametes, while a change in the phenotype associated with sex occurs as a whole. Dichogamy can be manifested both within one reproductive cycle and during the life cycle of an individual, while the reproductive cycle can begin either from the male or from the 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.