Sea saucer. The teeth of a limpet mollusk are the strongest material in nature.

Snails, or gastropods, constitute the most species-rich class of soft-bodied animals. There are about 90,000 species in this class. They populated both the coastal zone of oceans and seas, as well as significant depths and areas open sea; they settled in fresh waters and adapted to life on land, penetrating even rocky deserts, the subalpine mountain belt, and caves. Some modern groups of freshwater gastropods have gone through a very complex evolutionary path: they came out of sea waters onto land, acquired a new type of breathing in connection with this, and then went back to “ permanent residence"into fresh waters, retaining there, however, this type of breathing acquired on land. One of characteristic features Gastropods are distinguished by the presence of a solid shell, not divided into valves or plates and covering the back of the animal; it would be more correct to say that the shell covers here the so-called internal sac, i.e., a sac-like protrusion on the back, inside which there is a number of organs. Another typical characteristic of gastropods is that most of them have lost bilateral symmetry. The intestine of all modern gastropods forms a loop-like bend, and therefore the anus lies above the head or to the side of it, on the right side of the body. In most gastropods, the shell is twisted into a spiral, and the turns of the spiral most often lie in different planes. Such a spiral is called a turbospiral. The whorls of the shell form a whorl. In addition, they distinguish between the apex and the mouth - the hole from which the head and leg of the mollusk protrude. Accordingly, with the spiral twist of the shell, the internal sac is spirally twisted. In the vast majority of cases, the twist is observed in a clockwise direction, that is, to the right, when looking at the shell from its top; in more rare cases, the shell and visceral sac are twisted counterclockwise, i.e. to the left. Based on the direction of twisting of the shell, right-handed (dexiotropic) and left-handed (leotropic) shells are distinguished, and sometimes individuals of the same species can have both right- and left-handed shells. The shells of various snails are extremely varied in appearance, which is determined by the number and shape of the spiral turns, and how steep or gentle its turns are. Sometimes the whorls of the shell spiral, tightly adjacent to each other, grow together with their internal parts, forming a solid column (columella), sometimes they lag behind one another, due to which, along the axis of the shell, instead of a solid column, an umbilical canal is formed, which opens at the last whorl of the shell with a hole called navel Finally, in a number of cases we see in snails a seemingly simpler shell in the shape of a cap or saucer, but, as the history of development shows, such shells in modern snails are the result of a simplification of the initially spirally twisted shell. The violation of bilateral symmetry characteristic of most gastropods, i.e., the asymmetry of the organs of the visceral sac and mantle cavity (one gill, one atrium, one kidney), is caused by the turbospiral shape of the shell. With this shape of the shell, with the helix directed to the side, and with the fact that the bulk of the liver is located in the last turns of the helix, the center of gravity of the shell is shifted away from the midline of the body. Due to this, one of the sides of the open (estuarine) whorl of the shell is closer to the body than the other side, raised above it. All this resembles a hat worn on one side. But this position of the shell narrows the space of the mantle cavity on one side, which leads to the reduction of one of the gills and the associated atrium and, naturally, the kidney. The correctness of this explanation for the emergence of asymmetry in gastropods is confirmed by the fact that all stages of its development can be observed in modern primitive representatives. In some gastropods with a cap-shaped shell, bilateral symmetry of the entire complex of pallial organs is still preserved; in others, one or both ctenidia and the atrium can be seen to be reduced.

The shell of gastropods is covered with a thin layer organic matter, constituting its outer layer - periostracum. The latter sometimes forms bristle-like processes, making the shell appear shaggy from the outside. The part of the shell covered by the periostracum is composed of thin calcareous plates, which together make up the so-called porcelain layer, in which, in turn, up to three layers of calcareous plates can be distinguished. In some (a relatively small number) snails, the inner surface of the shell is lined with a shiny mother-of-pearl layer. Intraspecific shell variability of many gastropod species is very wide. This breadth of its variability shows the importance of the shell in ensuring the adaptability of individuals of the species to living in places with different combination environmental factors. The researcher of Black Sea mollusks V.D. Chukhchin showed the existence of differences in the shape of the shell and in its thickness between males and females of the same species.

Moving on to the consideration of the soft parts of the body of snails, first of all, it should be noted that they have a more or less separate head, bearing a mouth, eyes and tentacles, and on the abdominal side - a massive muscular leg with a wide lower surface, called the sole. The characteristic method of movement for most snails is slow sliding along the substrate on the sole of the foot, and the movement itself is carried out thanks to waves of contraction running along the sole of the foot from back to front. The abundant mucus secreted by the skin softens friction and facilitates sliding on a hard substrate. In some snails, due to their transition to a different type of movement, both the function and structure of the leg change. In many snails, the back of the leg bears a special horny or calcified cap on the upper surface, and when the snail hides in the shell, the cap closes the mouth. The shell is connected to the body with the help of a powerful muscle, the contraction of which pulls the snail inside the shell.

Directly under the shell, covering the internal sac, there is a mantle, the anterior thickened edge of which hangs freely over the body of the animal and covers the mantle cavity formed under it, into which the anal, excretory and genital openings open; holes. The mantle cavity also contains respiratory organs - most often one feathery gill, or cteninidia (a relatively small number of snails have two gills); in snails belonging to the pulmonate subclass, the gills are lost, and the roof of the mantle cavity functions as a lung. The free edge of the mantle in some snails can extend into a more or less long tube - a siphon, located in the siphonal outgrowth of the shell. In other cases, the free edge of the mantle may be folded over the edge of the shell, so that the mantle, protruding from under the shell, partially or completely covers it from above. In the latter case, the shell becomes internal and usually undergoes reduction to one degree or another. The snails' mouth leads into a voluminous oral cavity, which contains a paired or unpaired jaw and an organ typical of most mollusks - the grater, or radula. Paired ducts open into the oral cavity salivary glands, and in some snails - ducts and other glands, for example poisonous or acid-secreting. A thin esophagus extends from the oral cavity, in some snails it expands into a voluminous crop, and the latter passes into the stomach, into which the digestive gland (“liver”) opens. The intestine begins from the stomach, which is shorter in carnivorous gastropods and longer in herbivores. The intestine opens outward through the anus inside the mantle cavity.

The circulatory system of snails is not closed: the heart consists of one ventricle and one atrium (a few forms have two atria). The atrium collects oxidized blood from the gill or lung, from where it is distilled into the ventricle, and then distributed throughout the body through the branching cephalic and splanchnic aortas. The heart of the snail lies inside the pericardial cavity. The excretory organs, the kidneys, communicate with this cavity, and in rare cases they are paired. The nervous system of snails consists of 5 pairs of nerve ganglia, or ganglia: cerebral, leg, or pedal, pleural, visceral and parietal. The ganglia are connected by nerve cords: those of the same name - by the so-called commissures, and those of the same name - by connectives. In connection with the twisting of the visceral sac, in snails belonging to the prosobranch subclass, as well as in some of the lowest representatives of the other two subclasses (opisthobranch and pulmonate), a characteristic crossing of connectives is formed between the pleural and visceral ganglia. The higher opisthobranchs and pulmonates do not have this decussation. The convergence of various ganglia and the corresponding shortening of the connectives connecting them is very pronounced in many snails. In this case, all the ganglia located under the pharynx, including the pedal ganglia, form a compact group.

Of the sense organs, in addition to the eyes on the front pair of tentacles of the head and a pair of head tentacles, which have the significance of organs of touch, snails have developed balance organs - a pair of statocysts, which are innervated from the cerebral ganglia, although they lie in close proximity to the pedal ganglia. Statocysts are closed vesicles, the walls of which are lined with ciliated and sensory cells, and the cavity contains a liquid in which one large or many small grains of calcium carbonate float. The pressure that grains of calcium carbonate exert on one or another section of the wall of the bubble when various positions snail, allows it to navigate in space. Snails also have a chemical sense organ - the osphradium, which lies at the base of the gill and serves to sample water entering the mantle cavity. The second pair of head tentacles in land snails is the olfactory organ. In addition, the skin of snails is rich in sensitive cells. Gastropods have very well developed chemoreception. Specialized nerve cells of the tentacles, areas of skin near the mouth and osphradia provide remote recognition of food, return to a previously chosen place, and a sense of the proximity of predators, for example starfish or brittle stars, by their smell.

The reproductive system of representatives of different subclasses of gastropods has a different structure. Among snails there are both dioecious and hermaphroditic forms. In the latter, the structure of the reproductive apparatus is the most complex. Fertilization in most gastropods is internal. Gastropods have different spawning methods. The most poorly organized forms release eggs and sperm directly into the water, where fertilization occurs. Some species envelop eggs with mucus, forming cords, cocoons, and slimy shapeless masses. Such aggregations of eggs are most often attached by mollusks to a substrate - algae, empty shells and to the bodies of other aquatic animals, and buried in the ground of reservoirs. Terrestrial gastropods bury eggs in wet ground or attach them to the stems and roots of plants. The development of gastropods either occurs through the larval stage, which will be discussed later, or it is direct, i.e., a small mollusk emerges from the egg shells with an incomplete number of shell revolutions and an undeveloped reproductive system. But in all groups of gastropods, along with direct development, viviparity can also be found, when eggs develop in special parts of the mother’s reproductive system. In other cases of direct development, eggs are incubated under the protection of a shell or mantle until the young hatch.

Let us now return to cases of development of gastropods with the larval stage. In some, very few modern marine gastropods, a larva emerges from the egg - a trochophore, very similar to the larva of annelids. Trochophores are characteristic of the most simply organized gastropods (Patella, Gibbula). The free-swimming trochophores soon develop into the next larval stage, the veliger. In some gastropods, the trochophore stage takes place inside the egg membranes and the veliger larva or, as it is called, “sailfish,” emerges from the egg. The larva received this name for its movement with the help of highly developed sail-like blades of the mantle, the edges of which are covered with cilia. In different species of gastropods, veligers are carried out in the water column different times and because of this they are carried to different distances from the spawning site. The settling of larvae to the bottom is facilitated by chemicals secreted by other organisms with which gastropods usually live - cyanobacteria, corals, sponges, algae. These chemical signals perfectly demonstrate the complex relationships between different species that form part of biocenotic relationships. After the larva settles to the bottom, its metamorphosis occurs, i.e., the larva transforms into an adult mollusk. This is accomplished by shedding the larval skin with cilia, and in other cases by shedding other parts of the larva’s body. By this time, the body of an adult mollusk has already formed under the larval covers. There is evidence that metamorphosis is stimulated by chemical substances secreted by those organisms that are most characteristic in the usual habitats of this type of mollusk.

Many marine species of gastropods are eaten by fish - herring, sardines, mackerel. As Lebur points out, these fish eat especially heavily the planktonic larvae of gastropods. Other fish, such as gobies, destroy adult benthic gastropods. Birds are also not averse to eating gastropods; various waders that live on sea beaches and near fresh water bodies are especially active. Terrestrial gastropods are eaten by thrushes and some other birds, and among mammals - hedgehogs and moles, as well as reptiles. Gastropods are often attacked by predatory beetles, tahini flies, and fireflies. Flies and wasps use the empty shells of terrestrial mollusks to lay eggs. Sponges, bryozoans, sea acorns, hydroid polyps and other animals often use the shells of marine gastropods as a substrate on which their larvae settle. To date, there are different views on the taxonomy of the class of gastropods. The most natural groups of gastropods can be considered the following: subclass Prosobranchia, subclass Opisthobrauchia, subclass Pulmonata.

It is hardly possible to list all the prosobranchs that are eaten by the population of coastal regions of countries Southeast Asia, Africa, South America. Many species, such as littorina, buccinum, patella, etc., are still in great demand. The colorful, elegant shells of snails are used in the form of jewelry - beads, pendants. Cameos are cut out of them, and. colored hypostracum, dark brown in Cassis cameo, yellow in C. rufa, pink-red in Strombus gigas, stands out very impressively against the white background of the ostracum. Finally, Tchochus shells are used as raw materials for button production. All this, unfortunately, is associated with the destruction of a significant number of mollusks and leads to the destruction of natural communities.

SUBCLASS OSPISTHOBRANCHIA Opisthobranchia are significantly inferior to prosobranch mollusks in the variety of forms, but still constitute a rather species-rich group of gastropods. The most primitive representatives of this subclass retained some similarities with prosobranchs. This similarity is expressed not only in purely external signs of body shape or in the presence of a spirally twisted shell with a more or less elevated curl, but also in the anatomical features of the structure nervous system, gill apparatus and other signs. However, most of the opisthobranch species in the process of evolution deviated quite far from the original ancestral forms, which, as can be assumed, had typical features of prosobranchs. The mantle cavity in opisthobranchs, if present, is relatively small and located on the right side of the body. The atrium lies behind the ventricle, and the ctenidium lies behind the heart (hence the name “postobranchs”). In many opisthobranchs, the shell is overgrown with a mantle and undergoes reduction to one degree or another. In some forms it is reduced to a small plate of irregular shape lying under the mantle, in others it disappears completely. Only a very few, more primitive species have an operculum that closes the mouth. It is interesting to note that among shelled opisthobranchs there is a very large percentage of species with a left-curved (leotropic) shell. The leg of many representatives of the subclass changes greatly. There are a number of forms in which the leg is extremely poorly developed, and in some it is completely reduced. In others, on the contrary, the sides of the legs grow into wide wing-shaped blades, the so-called parapodia, which are used for swimming. The structure of the respiratory organs also undergoes drastic changes. Most often, in the various pestles of the body of opisthobranchs there are skin outgrowths - secondary gills that develop to replace the lost true ctenidia. Secondary gills are usually located symmetrically either around the anus, or on the sides of the back, or on the underside of a special thickening of the mantle on the back of the animal. Opisthobranchs may have a common characteristic feature in external form their bodies show some tendency to return to bilateral symmetry. This trait is manifested not only in pelagic forms, but also in forms that live on the seabed and move by crawling, like other mollusks. The anus of some opisthobranchs is located on the midline of the back. In some species the body is strongly elongated and laterally compressed, while in others, on the contrary, it is flattened in the dorso-ventral direction and acquires a general external resemblance with the body shape of flatworms turbellarians. A certain return to bilateral symmetry is also manifested in the structure of the nervous system: if in primitive representatives of the subclass, closer to prosobranchs, we still find the crossing of pleurovisceral nerve trunks typical of the latter, then in other opisthobranchs this feature is barely noticeable.

Among the sensory organs typical of mollusks, as a rule, there are balance organs (statocysts); The osphradium associated with the gill is present in representatives of the order Angiobranchia, to which the more primitive forms of the subclass belong. Characteristic of opisthobranchs are areas of skin on the head on the sides of the mouth with accumulations of sensitive cells, which apparently serve as organs of smell or taste. In a number of forms, the same functions are performed by sensitive cells located on the posterior pair of head tentacles (rhinophores). As organs of touch, some opisthobranchs develop tentacle-like appendages on the sides of the mouth. As for the eyes, although in most opisthobranchs they are developed, they are of secondary importance in these mollusks and are usually covered with skin. The heart of opisthobranchs consists of one ventricle and one atrium and lies in the pericardium. Only in one genus (Rodope) the heart is reduced. The unpaired kidney connects to the pericardial cavity, and its external outlet opens on the right side of the body or at the base of the gill. The gonads are hermaphroditic, and the reproductive apparatus is more complex than in prosobranchs. Puberty usually occurs during the second year of life, and after reproduction, the postbranchs quickly die. Among opisthobranchs we find both herbivorous forms and predators. Most animals have a well-developed radula, and some, in addition, have a mouth armed with a ring of spines or numerous hooks. Available salivary glands and the digestive gland, the so-called liver, which in some opisthobranchs is divided into many separate lobules. This organ serves to digest and assimilate food, particles of which are captured by cells (intracellular digestion). In some opisthobranchs, the muscular stomach has hard calcified plates on the inner surface, which serve for better grinding of food. Most opisthobranchs live on the seabed, on sandy or muddy ground, many close to the water's edge, so that at low tide they can easily be found among algae thickets or accumulations of hydroids. Species that usually stay at the bottom can, with the help of developed skin folds, rise above the ground and swim short distances. Opisthobranchs, part of the order pteropods, are typical planktonic animals. Representatives of the subclass of opisthobranchs are widespread in the seas, with most species living in warm seas and temperate seas, but many of them are also found in cold zones, and several species have adapted to life in estuaries (the islands of Palau and Flores in Micronesia).

SUBCLASS PULMONARY (PULMONATA) Pulmonary snails represent the group that has deviated most far from the common trunk of gastropods in the process of evolution. All pulmonate snails have adapted to life either on land or in fresh waters, and if some of their representatives are sometimes found in the seas, then only in highly desalinated areas. The shells of pulmonary mollusks are most often spirally twisted and very diverse in shape - from tower-shaped or valval to disc-shaped. In a relatively small number of species, the shell has taken the form of a cap covering the entire body on top, like in snails living in rivers with fast current. In other species, this cap covers only a small part of the body and is a rudiment of a shell, as we see in many land snails. Finally, in land snails we encounter cases where the shell is completely overgrown with the mantle, sometimes accompanied by the complete disappearance of the shell. In species with a well-developed shell, it exhibits a clear spiral twist and is usually twisted to the right; however, there are groups of pulmonate snails in which the shells are twisted to the left, and specimens with a right-handed shell are an exception. The mouth of the shell usually remains open, since the operculum is preserved only in representatives of the family Amphibolidae. In a small ancient group of land pulmonate snails of the family Glausiliidae, the mouth is closed by a special shell valve - the clausilium, which rests on a complex system of plates. Clausilium superficially resembles the operculum of prosobranchs, but it is of a completely different origin. Another way to protect against unfavorable conditions environment, for example from drought or cold, serves to tighten the opening of the shell with a film of mucus containing calcium, hardening in the air, the so-called epiphragmon. Between the membrane and the body of the snail, which is deeply drawn into the shell, there usually remains a layer of air. The degree of reliability of the protection created in this way can be judged from the data of experiments during which garden snails were exposed to low temperatures. Under the protection of the epiphragm, the snails endured temperatures of 110 and 120 °C below zero for several periods, with the exception of those specimens in which this phragm was cracked. In addition, there are known examples of land snails surviving extreme heat and drought thanks to this adaptation. The abundant and rapid secretion of mucus necessary for the formation of the epiphragm is facilitated by the so-called “teeth” of the mouth, especially characteristic of species living in dry conditions. In some species, the teeth are represented by very numerous strong convexities on the inner wall of the mouth, in others they look like thin and sharp plates extending along the inner wall of the whorl far into the depths of the shell. All these formations, when the body of the snail is pulled into the shell, press on the soft tissues and squeeze out the mucous secretion, which forms the epiphragm. When unfavorable conditions occur, aquatic pulmonary snails resort to blocking the mouth of the shell, which also closes the opening of the shell with a layer of mucus with an air gap between it and the body; This is how they sometimes even freeze into the ice and survive the winter without harm to themselves. Shellless land snails, the so-called slugs, are much less protected in this regard. Severe drought, bright sunlight in the summer heat, severe cold, force slugs to look for shelters under various covers, for example, under a layer of fallen leaves, in cracks under the bark in rotting stumps, or to hide between clods of soil, sometimes climbing quite deep into the ground; moisture is retained there and temperature fluctuations are less severe. All pulmonary snails are characterized by smooth gliding movement on the soles of their feet, in the front part of which there is a highly developed gland that secretes mucus. The latter wets the sole and protects its skin from damage, reducing friction on the hard surface of the substrate. The forward movement of the cochlea occurs due to wave-like contractions running along the soles from back to front, caused by the interaction of the longitudinal and sweat muscles. Moving forward, the mollusk usually extends its tentacles using them as a sense of touch. In freshwater forms, the head has such tentacles, at the base of which there is a pair of eyes. Land snails often have two pairs of tentacles, and some forms also have a third pair - tentacle-like appendages located at the edges of the mouth. The eyes of terrestrial animals are located differently than those of freshwater ones at the ends of the tentacles. Of the other sense organs, balance organs are developed - statocysts. Aquatic forms also have a poorly developed osphradium.

One of characteristic features pulmonary mollusks, which determined the name of the subclass, follows the respiratory system and the transformation of the cavity into a lung. This occurs by fusion of the free edge of the hanging mantle with the cover of the front part of the body so that a small respiratory opening remains - the cneumostome, through which the mantle cavity communicates with external environment; the walls of the cneumostoma can close. The fusion of the mantle with the integument occurs in the early stages of embrygenesis, which indicates the antiquity of the origin of pulmonary mollusks. On the inside of the mantle cavity, on the inside, there is a dense plexus of vessels into which oxygen enters through diffusion. Gills in pulmonate snails are found only as an exception. Thus, terrestrial and freshwater pulmonary mollusks breathe atmospheric air, in connection with which freshwater forms must from time to time rise to the surface of the water and draw air into the mantle cavity. The heart of pulmonary snails consists of one ventricle and an atrium. The nerve ganglia are more or less clearly concentrated and form a peripharyngeal ring. Among pulmonate snails we find herbivorous, omnivorous, and predatory species. Predatory pulmonate mollusks feed on other snails and sometimes on worms. Pulmonary snails have a well-developed radula, and herbivores also have an unpaired horseshoe-shaped jaw. The teeth on the radular plates are especially long and pointed and resemble the shape of vertebrate fangs. The pharynx is well developed. The ducts of the salivary glands open into it. The digestive gland, the liver, flows into the muscular stomach. The intestine forms a loop, and the anus is usually located near the inhalation opening on the right side of the body. Next to the anus there is usually the external opening of the only kidney, which is connected to the pericardium. The reproductive apparatus of pulmonate snails is particularly complex. The gonad is hermaphroditic. The common duct extending from it is then divided into male and female parts, both of which have a number of adnexal formations. The female part includes the albuminous and shell glands, the spermatic receptacle, and sometimes a number of other glandular appendages. The most highly organized representatives of the subclass have a complex male copulatory organ. Some species are characterized by the formation of spermatophores, i.e., special receptacles for the seed. When mating, both partners mutually fertilize each other, and the mating itself is usually preceded by “love play.” In some forms, during mating, special calcareous needles penetrate into the body of the partner - “love arrows”, which serve for sexual arousal. They are formed in special sections of the reproductive system - the bags of “love arrows”. Pulmonary snails lay eggs either in a common gelatinous cocoon of one form or another (freshwater species), or separately, although in a common clutch (terrestrial species). Each egg is surrounded by a significant supply of nutritional material, and in some forms the ratio of the mass of the egg to the mass of the surrounding protein is 1: 8000 (in Limax variegatus). Development occurs without a free-swimming larval stage; An almost fully formed snail emerges from the egg. Pulmonary snails are divided into two orders.

Scientifically they are called patella, in simple terms they are called sea snails or limpets, and in Madeira, where these flat-shelled mollusks are considered a local delicacy, they are called lapas. In fact, sea limpets are found not only on a remote island in Atlantic Ocean- no, they can be found in abundance in both the Black and Mediterranean Seas, where they live on coastal rocks. To tear a mollusk away from the stone it is holding on to, it takes a lot of effort - the slightest touch, and the limpet is pressed against the stone, so much so that it is almost impossible to tear it off without a knife. But what to do if there is no sea or a bay with sea limpets a stone’s throw from your home, and it’s not in sight?.. The answer is very simple - prepare mussels according to this recipe, which (unlike sea limpets) can also be bought frozen.

Sea saucers with garlic butter

First, it is advisable to clean the sea limpets (although in Madera, it seems, they do without this at all). Take a small knife, pick up the clam with it and immerse the knife to the middle of the shell, then, turning the shell, run the knife along the entire radius to separate the clam from it. Underneath you will find a “bag” with unappetizing black and green contents: the bag must be thrown away, and the elastic mollusk must be returned to its shell.

Cut the butter into small cubes according to the number of shellfish, and chop the garlic and parsley very finely and mix thoroughly. Transfer the sea limpets to a baking dish, add a cube of butter to each, a pinch of parsley-garlic mixture and season with salt and black pepper. Preheat the oven grill to high and place the pan under the grill. Remove after a few minutes, just after the butter has melted and bubbled.

Serve limpets (or lapas, as the Portuguese call them) as a hot appetizer, with white wine and white bread for dipping.

In general, the locals told me that these shellfish can be eaten raw, simply by peeling and sprinkling lemon juice. Looks like it's true.

Real sea limpets living in sea basins; however, conical shells arose several times during the evolution of gastropods in various clades with gill and pulmonary respiration. The name comes from the characteristic “saucer-shaped” shape of the shell. Many mollusks that have such a shell belong to different taxa:

Patellogastropoda (English)Russian, for example Patellidae (English)Russian
Vetigastropoda (English)Russian, for example Fissurellidae (English)Russian, Lepetelloidea (English)Russian
Neritimorpha (English)Russian, for example Phenacolepadidae (English)Russian
Heterobranchia, group of Opisthobranchia, e.g. Tylodinidae (English)Russian
Heterobranchia, Pulmonata group e.g. Siphonariidae, Latiidae, Trimusculidae (English)Russian

A study of limpet teeth has revealed that they are the most durable biological structure known.

Real sea limpets

The term "True limpets" (English)Russian» used only in relation to marine mollusks of the ancient clade Patellogastropoda (English)Russian, which consists of five modern and two fossil families.

Use of a colloquial name

Along with true sea limpets, the term "sea limpets" is applied to a number of other snails whose adult shells are not coiled. The term "false limpets" is also used.

Marine representatives

Keyhole saucer (English)Russian- Fissurellidae (English)Russian
Inhabitants of underwater hydrothermal vents - Neomphaloidea (English)Russian and Lepetodriloidea (English)Russian
Neritids - Phenacolepadidae (English)Russian
Calyptraeidae (English)Russian
Hipponix (English)Russian and other Hipponicidae (English)Russian
Tylodina (English)Russian
Umbraculum (English)Russian

Two groups of false limpets with pulmonary respiration
- Trimusculidae (English)Russian

Freshwater representatives

River and lake animals with pulmonary breathing - Ancylidae (English)Russian

Most marine species have gills, while all freshwater and some marine species have a mantle cavity, which functions as a lung (in some cases, it has been re-adapted to release oxygen from the water).

Thus, the term "limpets" applies to a large, heterogeneous group of gastropods that have independently evolved to have similar shell shapes.

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Notes

An excerpt characterizing the limpet

- Signal! - he said.
The Cossack raised his hand and a shot rang out. And at the same instant, the tramp of galloping horses was heard in front, shouts from different sides and more shots.
At the same instant as the first sounds of stomping and screaming were heard, Petya, hitting his horse and releasing the reins, not listening to Denisov, who was shouting at him, galloped forward. It seemed to Petya that it suddenly dawned as brightly as the middle of the day at that moment when the shot was heard. He galloped towards the bridge. Cossacks galloped along the road ahead. On the bridge he encountered a lagging Cossack and rode on. Some people ahead - they must have been French - were running from the right side of the road to the left. One fell into the mud under the feet of Petya's horse.
Cossacks crowded around one hut, doing something. A terrible scream was heard from the middle of the crowd. Petya galloped up to this crowd, and the first thing he saw was the pale face of a Frenchman with a shaking lower jaw, holding onto the shaft of a lance pointed at him.
“Hurray!.. Guys... ours...” Petya shouted and, giving the reins to the overheated horse, galloped forward down the street.
Shots were heard ahead. Cossacks, hussars and ragged Russian prisoners, running from both sides of the road, were all shouting something loudly and awkwardly. A handsome Frenchman, without a hat, with a red, frowning face, in a blue overcoat, fought off the hussars with a bayonet. When Petya galloped up, the Frenchman had already fallen. I was late again, Petya flashed in his head, and he galloped to where frequent shots were heard. Shots rang out in the courtyard of the manor house where he was with Dolokhov last night. The French sat down there behind a fence in a dense garden overgrown with bushes and fired at the Cossacks crowded at the gate. Approaching the gate, Petya, in the powder smoke, saw Dolokhov with a pale, greenish face, shouting something to the people. “Take a detour! Wait for the infantry!” - he shouted, while Petya drove up to him.
“Wait?.. Hurray!..” Petya shouted and, without hesitating a single minute, galloped to the place from where the shots were heard and where the powder smoke was thicker. A volley was heard, empty bullets squealed and hit something. The Cossacks and Dolokhov galloped after Petya through the gates of the house. The French, in the swaying thick smoke, some threw down their weapons and ran out of the bushes to meet the Cossacks, others ran downhill to the pond. Petya galloped on his horse along the manor's yard and, instead of holding the reins, strangely and quickly waved both arms and fell further and further out of the saddle to one side. The horse, running into the fire smoldering in the morning light, rested, and Petya fell heavily onto the wet ground. The Cossacks saw how quickly his arms and legs twitched, despite the fact that his head did not move. The bullet pierced his head.
After talking with the senior French officer, who came out to him from behind the house with a scarf on his sword and announced that they were surrendering, Dolokhov got off his horse and approached Petya, who was lying motionless, with his arms outstretched.
“Ready,” he said, frowning, and went through the gate to meet Denisov, who was coming towards him.
- Killed?! - Denisov cried out, seeing from afar the familiar, undoubtedly lifeless position in which Petya’s body lay.

Teeth a common type of mollusk limpet (Patella vulgata) stronger than Kevlar and stronger than spider silk, scientists report in the February 18 issue of The Royal Society Journal.

Limiters are hardy little molluscs that are ubiquitous in our planet's oceans. Their conical shells protect the stalk, which they use to attach themselves to underwater rocks with incredible strength. The limpets feed on algae by releasing a long tongue lined with hundreds of sharp teeth that scrape food particles off rocks.

A research team from the University of Southampton, England, led by mechanical engineering professor Asa Barber, examined microscopic fragments of the mollusc's teeth. Each curved tooth is about 1 millimeter long and is about 100 times thinner than a human hair.

According to Barber, the secret to the strength of these teeth lies in the size of the fiber structures that form it. As long as the dimensions of these fibers are below a certain critical length, their strength remains unchanged, even if their material contains defects. They themselves are a biological composite of goethite (mineral iron oxide) and chitin, which plays the role of natural plastic.

As a result of this combination, teeth made of this material can withstand a load equivalent to 1,500 kilograms suspended on a spaghetti-thin thread.

The next task for scientists will be to reproduce the mechanism by which limpets create these unique materials. And although spider silk has proven incredibly difficult to imitate in the artificial environment, researchers believe that limpet tooth fibers can be 3D printed.

Spider silk is one of the most durable natural materials. Its fibers have a specific strength five times higher than the best varieties steel, and at the same time they can stretch freely. The strongest known silk is produced by Darwin's tree spiders, which are found in Madagascar - their silk is 10 times stronger than Kevlar. To put things into perspective, the mineral teeth of the limpet are stronger than this silk by about 10 percent.

The sea limpet is a typical inhabitant of the surf zone of the Far Eastern seas. It is found on coastal stones and rocks, tightly adhering to their surface, usually in shallow recesses and crevices.

The shell of a limpet consists of one valve, spirally curled to the right or left, and on its surface, also spiraling around, there are clearly visible growth lines. As a rule, their number does not exceed twenty, by which one can judge the probable age of the mollusk. The shape of the shell can be very diverse: slightly flattened, with the apex shifted to the side, or, conversely, a towering regular pyramid...

In general, this mollusk is characterized by a simplified symmetrical shell, shaped like a cap or a saucer turned upside down, which is why it got its name. True, it would be a stretch to call such a shell a saucer, well, if only it served in this capacity for some tiny sea bird, for example, a storm petrel. Despite its apparent fragility, the shell of the limpet is very strong and is able to withstand the constantly incoming stubborn waves, without fear of the strongest surf.

Of course, the shape of the limpet shell is quite primitive, and yet these mollusks attract attention precisely because of the simplicity of their house, which seems very charming and secluded. The persistent waves are unable to knock these shells off the coastal stones, the sea water, as if angry at the rebellious inhabitants coastal strip, flows freely from their smooth conical walls, and the tops of the shells are sharply pointed, no matter what, they are always tuned to growth. I just want to tear the sea saucer off the rock and look - what is inside it?

Whether the tide is approaching or the tide is going out, outwardly the saucers do not react in any way to what is happening and from the outside they look like creatures completely indifferent to everything, even lazy. This is their original habitat, where they live, firmly attached to the coastal rocks, it seems, from time immemorial. Cone-shaped shells with bluish-gray, beige and cream tops are pressed against the stones so tightly that it is impossible to squeeze a knife blade between them. Even when the rocky surface turns out to be rough and uneven, the edges of the shell also become uneven and jagged, following all the irregularities of the stone, which gives the mollusk the opportunity to press tightly.

When a mollusk is disturbed, it presses against the stone on which it sits with enormous force, and in order to overcome the suction force of this ordinary small shell, you need to drive a sharp iron object between the shell and the stone. Then, using it as a lever, you should try to separate the mollusk from the stone, which most often breaks it: the attached leg remains on the stone, and the shell with the mantle and entrails comes off. But if the mollusk sits with its shell raised so that its head and side parts of the body remain open, then a light blow is enough for the saucer to separate from its attachment site.

For a long time, it was considered unclear how the limpet is attached: whether it is glued by the secretion of special glands, or is held in place solely by the shell muscle. It is now known that at first, indeed, mucus is secreted from the many skin glands of the sole of the foot, which serves to fill small gaps between the sole and the stone, and only after that the concha muscle begins to act with all its force, the ring shape of which is only broken in front by a small notch, thanks to why it resembles a horseshoe. The muscle tenses with every wave of the surf, as well as during the entire low tide, while the mollusk is exposed to sunlight.

Previously, there was an erroneous belief that, due to its very strong attachment to the rock, the limpet supposedly never changes its place. However, it turned out that the mollusk still travels, albeit only at night. It is remarkable that, moving in a certain way always to the left, he eventually returns to the starting point of his path and strengthens himself in the old place in the same way as he sat there before. When moving, the mollusk is helped by a uniform deviation from a straight line and its orientation in the endless sea space is limited to just a meter!

The limpet is very attached to its place of residence. It turns out that only if the place where the mollusk lives has undergone fundamental changes during his absence, he decides to search for something new and in no case settles anywhere. When choosing a more convenient place, the mollusk is guided by the need for air sufficiently saturated with water vapor, and therefore prefers crevices in stones, especially their shadow side. But what forces the sea limpet to travel, and even at night?

The nocturnal wanderings of the sea limpet serve primarily to satisfy hunger, and doing this at night is less safe. During its movement, the mollusk eats the surface of the rock, and the gnawed strip reveals its path, because all the time while the animal is crawling, its radula, which are thick, strong blades - an excellent scraping tool, is constantly in action. The mollusk feeds on various microorganisms that grow on rocks, and along the way, small plants such as ulva and fucus, but it does not look for them on purpose, eating mainly everything that it can shave off the surface of the stone with its radula along the way. Its strong teeth fully correspond to its purpose in the surf rocky zone, but this work, however, leads to extremely rapid wear of the tool, and when it is completely worn out, the mollusk dies from the inability to feed, after which its shell falls off, replenishing the empty shell rock at the surf strip, where it is imperceptibly ground into the sand by the waves.

But along the shores of the Seas of Japan and Okhotsk there are so many limpets, and scientists have discovered at least 11 species of them here, that there is no need to fear: this mollusk will never run out. The largest of the sea limpets, the pale acmea, is found off Southern Sakhalin and the Southern Kuril Islands. Its strong, thick-walled, almost snow-white shell reaches 6-8 centimeters in length.

When such a shell, already without a mollusk and carefully licked by the sea, falls into your hands, you want to weigh it in your palm, run your finger along the smooth inner walls, ultimately not knowing what to do with it next? But you are not able to get rid of the shell right away and again begin to turn it over in your hands, examining and admiring it until you take it as a souvenir to give it to some person you know well. I remember that I collected a great many of these saucers, because they were all attractive with their shape or color, and I stopped in my hobby only when I realized that the shells began to repeat each other. Many of them now lie in my closet, behind glass, and sometimes for some reason I touch their cool sides or even pick them up, returning them with regret. You won’t believe it, the limpets are still quietly emitting the light roar of the rolling surf, and it seems to me that they are not at all worried that I deprived them of their beloved Sakhalin coast...

And I again remember the rugged island shores with deep creeks and black rocks, sand spits and underwater ridges, densely covered with sea limpets... Small conical shells made of fragile limestone always for some reason made me timidly want to smile. Maybe because they steadfastly resist the persistent surf, and also resemble the so-called “Chinese hats” made of straw, with the help of which Chinese and Japanese fishermen usually save themselves from the sun while working, and shellfish from numerous enemies. Thanks to the acmea, tightly clinging to the wet stones, hardworking Asian residents appear in your memory, and when you see the Japanese or Chinese in straw hats, the graceful shells of sea limpets that live near the sea appear before your eyes. This is probably due to the surprisingly similar forms and the fragile charm of the lines, containing the sensitive laconicism of ordinary natural truth, which does not seek to embellish itself, but only wants to defend itself. In a word, there is something very touching in the sea limpets that is impossible to explain.

Some acmea shells are so expressive in their color that at first you will even mistake them for sea snails or litorinas: in the very middle, at the top, they have bluish tint spots, bordered tender greens, reminiscent of algae thrown out after a storm. The surprisingly discreet and gentle combination of these colors even seems to enlarge the shell, making it more alive. The mollusk itself is not visible, but its house is distinguished by its grace, and therefore the owner of this house is also perceived as graceful and sweet. A small, pea-sized mollusk, judging by its habitat, lives in it quite reliably and joyfully, like a magic pearl.

The tender name of the shell is acmea, and its neat design, decorated by nature appearance evokes an equally touching phrase - cameo... A stone decoration with artistic carvings and a convex image, most often it is onyx or agate... And sometimes, oddly enough, an elegant cameo brings back memories of the sea, while at the sight of the acmea itself, sensitively attached to the wet stone, one remembers an exquisite jewel, without which it is impossible to imagine a reverent attitude towards any beauty. The beauty of the sea carries many priceless surprises, and all of them make up its mysterious, enchanting bliss. The sea itself is an unsurpassed blue pearl framed by red, black and grayish-green coastal granite.

More often, however, acmea remains discreet, completely unnoticeable, well, if only you pay attention to it at low tide, when shells and stones that have not yet dried out shine with their true colors. Having in its very middle, at the top, a bluish-smoky coating, which also appears as a radiant lake surrounded by dark rocky shores, acmea, in miniature, resembles the sea that gave birth to it. But then a light breeze from a land unknown to her will fly in, dry the shell, and it will shut down again, becoming completely inconspicuous. Who will pay attention to this discreet beauty now?

I have always liked to note these inconspicuous manifestations of marine life, look at them and remember them. This is how I once became acquainted with acmea, at first not knowing what this neat, graceful shell is called, and when I heard its unusual name, even for the sea, I rejoiced even more with the overwhelming joy of being near the sea world. What is not hidden in it, and here you go, such an inconspicuous and touching given - acmeia! Something airy, but also strong, inseparable from the gloomy stone shores, in a word, subtle and strict. Akmeya... Enchanting underwater dreams, the dream of an unknown mollusk lulled by sea waves, its unwavering commitment to unbending rocks...

Although the acmea shell is fragile and elegant, it is not easy to separate it from these stubborn, gloomy and wave-rolled boulders. Acmea itself resembles a sea pebble nestled comfortably in some crevice, and I never had the desire to deprive the shell of its habitat. Only once did I try to separate with an underwater knife one of the shells with a blue tip that I liked, but I almost broke the tip of the blade while I tore off several mollusks, a good half of which I simply crumbled: the shells were tightly attached to the stones, and it was better to pick up those that were already detached, empty, than to disturb the living. True, the old limestone houses already looked nondescript, they were mostly of a dirty gray color, and only those worn out by the sea over a long time became snow-white, and the shape of the shells still remained conical, sublime, as if rushing, no matter what, to something unattainable and beautiful.

In general, while at sea I constantly had the feeling that it knew everything about me, knew that I would never forget about it, and someday I would write about its currents, fogs and winds, animals living in the depths and mysterious thickets of algae, I will mention , of course, about stones, especially about shells. The shells and stones felt me in some unimaginable way, did everything so that I would discover them at some appropriate moment, and even if I didn’t take them with me, I would definitely examine them by picking them up and then carefully returning them to their place. Everything that surrounded me in the sea and next to it was alive, it radiated its invisible energy, which I sensed with an inexplicable instinct, and from this mutual understanding with your native element, life became even more joyful.