The small pond is similar to an ordinary pond, only the size of the shell is smaller (see appendix Fig. 25). There is a small pond in temporary ponds - puddles, ditches, in swampy meadows, sometimes even on moist soil near the water edge. In a word, there are many places where a temporary resident is found.

It feeds, like its relative, algae and microorganisms.

A small pond is common throughout Europe and North Asia, as is an ordinary pond.

Gastropods

coil family;

horn coil.

Coils (Planorbis) belong to the class of gastropods (Gastropoda), to the order of pulmonary (Pulmonata), to the family of coils (Planorbidae).

The coil can be distinguished at a glance due to its extremely characteristic
a shell curled in one plane in the form of a spiral cord.
The horn coil (P. corneus L.) attracts the most attention, the largest among the others (shell diameter 30 mm, height 12 mm), reddish-brown. This coil is found everywhere in both pond and lake waters.
The movements of the coils resemble the movements of the pond. Crawling, the snails expose their dark soft body far from the shell and move around underwater objects with their wide flat legs. On the head there is a pair of thin tentacles, at the base of which eyes are placed. Coils are exactly the same as ponds, they can wander along the surface of water bodies, hanging from a film of surface tension of a liquid.
Coils breathe atmospheric air, absorbing it into the pulmonary cavity formed by the walls of the mantle. The respiratory opening leading to the specified cavity opens on the side of the body, near the edge of the shell. It opens when the coil rises to the surface of the water for a supply of air. With a lack of air, the coil uses a special leathery outgrowth, which is placed on the body near the pulmonary opening and plays the role of a primitive gill. In addition, the coil, in all likelihood, breathes directly through the skin.
Nutrition. Coils feed on plant foods, eating parts of plants that are scraped off with a grater. Especially willingly, these snails eat a green coating of small algae that forms on the walls of the aquarium. Outside, it is easy to observe through the glass how the animal acts with its grater, raking the plaque like a spatula. It is very possible that coils can feed on animal food. At least in captivity, they willingly pounce on raw meat.
Reproduction. Coils reproduce with eggs, which are laid on the leaves of aquatic plants and other underwater objects. The laying of the horn coil is constantly found on excursions and is so characteristic that it can be distinguished without difficulty: it has the appearance of a flat gelatinous plate of an oval shape yellowish or light brown in color and contains several tens of round pinkish transparent eggs. After two weeks or more (depending on the temperature of the water), tiny eggs are removed from the eggs, which grow quite quickly. The caviar of coils, like other snails, is readily eaten by fish and killed by them in a large number. Like a pond, coils are hermaphrodites.
Interesting is the behavior of the coils during drying of the reservoirs in which they are found. They dig into wet sludge, like a large horn coil (P. corneus). Sometimes this coil remains on the surface of the soil, sucking the mouth to the sludge if moisture remains in it, or releases a dense water-insoluble film, which closes the hole in the sink. In the latter case, the body of the mollusk gradually shrinks, eventually occupying the third part of the shell, and the weight of the soft parts drops by 40-50%. In this state, the mollusk can survive out of water for up to three months (edge \u200b\u200bcoil P. marginatus P. planorbis).

The body of the coil, like that of the pond, is divided into three parts: head, trunk and leg (see appendix Fig. 26). The leg is the muscular abdominal part of the body, resting on which the mollusk slowly glides. The coils of the shell coils are located in the same plane. The coils are not as mobile as the ponds, and can not be suspended from the surface film.

Coils live on plants in standing and slow-flowing reservoirs, in the same place as an ordinary pond, but rises to the surface of the water much less often.

beauty family;

larva of a beauty girl.

On a sunny day, blue lights flare up or down, over the river (see the appendix of Fig. 27). This is a flashing elegant dragonflies. At some point, they resemble helicopters.

The body is bronze-green, the wings of the females are light smoky, the males are almost entirely blue.

All dragonflies, wherever they are, wherever they fly, need water. They lay eggs in the water. And only in water can their larvae live. Larvae are not like adult dragonflies. That's just their eyes are the same.

About the eyes of dragonflies, I must say especially. Each eye consists of thousands of small eyes. Both eyes are large, bulging. Thanks to this, dragonflies can look in all directions at the same time. It is very convenient when hunting. After all, dragonflies are predators. And their larvae that live in the water, too.

Dragonflies prey in the air - they grab insects on the fly. Larvae live in the water, and here they also get their own food. But they do not chase after prey, but watch over it. The larva sits motionless or slowly crawls along the bottom. And tadpoles or insects of some sort pass by. It seems that the larva does not care about them, but how will this tadpole or insect turn out to be close. Time! She instantly throws out her long arm and grabs the prey, quickly drawing it to herself.

“But insects have no hands,” you say. And you will be right. Yes, of course, they have no hands. But there is a very long lower lip with hooks at the end. The lip folds like a hand at the elbow when you press the brush to the shoulder. And while the larva watches for prey, the lip is not visible. And when the prey is close, the larva instantly ejects the lip to its full length - as if shooting it - and grabs a tadpole or insect.

But there are times when the larva must be saved. And then speed saves her. More precisely, the ability to move from place to place with lightning speed.

Some predator rushed into the larva. Another second - and the larva disappeared. But where is she? Just been here, and now in a completely different place. How did she end up there? Very simple. Powered its "jet engine".

It turns out that dragonfly larvae have a very interesting adaptation: a large muscular bag inside the body. The larva absorbs water into it, and then throws it with force. It turns out a water "shot." The water stream flies in one direction, and the larva itself - in the opposite direction. Just like a rocket. And so it turns out that the larva makes a lightning jerk and escapes from under the very "nose" of the enemy.

Flying a few meters, the larva slows down, sinks to the bottom or clings to some plant. And again he sits almost motionless, waiting, when it will be possible to throw out the "arm" and grab the prey. And if it is needed, it will again launch its "jet installation". True, not everyone has a "jet engine", but only the larvae of large dragonflies.

After a year, the larvae of some dragonflies, after three years, the larvae of others are selected by some plant sticking out of the water to the surface. And then a small miracle happens: the larva skin bursts and a dragonfly appears from it. The most real and not at all like a larva.

The dragonfly will drop the skin like a suit, and even pull the legs out of stockings. He will sit for several hours, rest, spread his wings and go on the first flight.

Some dragonflies fly away from their birthplace. But the time will come, and they will definitely return. Because they cannot live without a river or lake, a pond or a swamp - without water, in a word. And a river, a pond, a lake also cannot live without these friends.

Dragonfly eggs are laid in water or in the tissues of aquatic plants. Extremely characteristic larvae hatch from eggs, interesting in their biological characteristics. These larvae play an important role among other living material of freshwater excursions.
Dragonfly larvae are found everywhere in stagnant and slowly flowing water. Most often they are on aquatic plants or on the bottom, where they sit motionless, sometimes slowly moving. There are species that dig into silt.

Larvae move either swimming or crawling. Larvae from the group of lyutki swim differently than others. The expanded gill plates located at the posterior end of the abdomen, which serve as an excellent fin, play a large role in movement. Curving a long body, the larva hits the fin with water and quickly pushes forward, moving like a small fish.

Dragonfly larvae feed exclusively on live prey, which they watch for hours on end motionless, sitting on aquatic plants or at the bottom. Their main food is daphnia, which they eat in large quantities, especially by younger larvae. In addition to daphnia, dragonfly larvae willingly eat water donkeys. They are less willing to consume cyclops, perhaps due to the size of the latter.
The favorite food of dragonfly larvae are also the larvae of mayflies and larvae of mosquitoes from the family of kulitsid and chironomid.
They also eat the larvae of water beetles, if only they are able to master them. However, large larvae of swimmers, well-armed and no less predatory, they do not touch, even if they are planted in a common vessel with them.
Dragonfly larvae do not chase their prey, but sit motionless on aquatic plants or at the bottom and guard the prey. When approaching daphnia or another animal suitable for food, the larva, without moving from place, throws out the mask with lightning speed and grabs its prey.

To catch prey, the larvae have a wonderful oral apparatus, which bears the successful name of “mask”. This is nothing but a modified lower lip, which has the form of grasping forceps sitting on a long lever - the handle. The lever is equipped with an articulated joint, so that all this device can be folded up and in a calm state covers the underside of the head like a mask (hence the name). Noticing the prey with his large bulging eyes, the larva, without moving from its place, takes aim at it and throws its mask far ahead with a lightning movement, grabbing the victim with remarkable speed and accuracy. Caught prey is devoured immediately by strong gnawing jaws, while the mask brings the victim to his mouth and holds it during the meal like a hand.

Breath. Dragonfly larvae breathe with tracheal gills. In lute-type larvae, the gill apparatus is placed on the posterior end of the abdomen in the form of three thin expanded plates penetrated by a mass of tracheal tubes. Shortly before the hatching of an adult dragonfly, the larvae begin to breathe also atmospheric air with the help of spiracles that open on their upper side of the chest. This explains why adult larvae often sit on aquatic plants, exposing the front end of their bodies from the water.

Lute-type larvae have the ability to discard gill plates in case of their infringement. This is not difficult to verify from experience: put the larva in water and squeeze the gill plate with the tip of the tweezers. This phenomenon is called self-healing (autotomy) and is well known in many animals (spiders, lizards, etc.). For this reason, it is necessary to catch larvae from the water that lack 1 - 2, and sometimes all 3 tail plates. In the latter case, breathing is performed, in all likelihood, through a thin skin dressing the body. The torn plate is restored again after some time, due to which it is possible to observe larvae with gill plates of unequal length. It should be noted that in Calopteryx one of the plates is always shorter than the other two, which is not an accidental circumstance, but a generic attribute.

Dragonflies breed with eggs that females lay in water. Masonry different types very diverse. Dragonflies, such as rocker arms and cradles, lay their eggs in the tissues of aquatic plants. In this regard, their eggs have a characteristic elongated shape, and the stuck end is pointed. In the place where the egg is stuck, a trace remains on the surface of the plant, which then takes the form of a dark speck or scar.
Since the eggs of different species of dragonflies are arranged on the plant in a certain order, peculiar, sometimes very characteristic patterns are formed.

Dragonfly suborder;

family of lyutka; groom-bride.

Very slender, elegant, elegant dragonfly (see. Appendix Fig. 28). The body is green, metallic-shiny. Females have yellow sides, breasts, and males with bluish-gray tinge.

There are no significant differences between dragonflies, and all descriptions of dragonflies and their larvae coincide, therefore, in the previous chapter you can find all descriptions of both larvae and adult individuals.

Mayfly Squad;

Mayfly ordinary.

Quiet summer eveningswhen the sun's rays are no longer burning, some insects, similar to butterflies, but with two or three long threads on the tail, swarm in the air off the banks of rivers, lakes and ponds (see appendix Fig. 29). They soar upward, then freeze, stabilizing the fall with long tail filaments, then, spreading wide wings, slowly sink down. So they swirl over the shore, like a dense fog or cloud about ten meters high, and about a hundred meters long. These swarms rush over the water like a storm. You will not see such an exceptional phenomenon every day, only in July-August it is repeated several times.

This dance, performing a mating flight, mayfly. Their wings and they themselves are so tender that it is simply amazing how they do not break during the flight. Involuntarily you think that they will not live long. And this opinion is true: many mayflies live only one day. Therefore, they are called mayflies, and their scientific name comes from greek word "ephemeron" - a fleeting.

After the mating flight, the females lay their eggs in the water and die. With such a short life, they do not eat anything.

Mayfly larvae develop in water. Larvae live longer, two to three years. And unlike an adult, they eat very well. And they feed on algae, decomposing organic matter, small invertebrates and during their development they molt up to twenty-five times. Many fish feed on larvae of mayflies, and various birds eat adult mayflies.

On examination, first of all, the quick, sharp movements of the larva are striking. Being alarmed, she headlong breaks away and swims very swiftly, moreover, three feathery tail filaments richly pubescent with hairs serve as fins (С1оёон, Siphlurus). The legs are mainly used for attachment to aquatic plants. The quick movements of the mayflies are likely to protect them from their many enemies, who are actively hunting for these gentle larvae. The protective role is probably played by the color of the larvae, generally greenish, suitable for the color of aquatic plants, among which they huddle.

The breath of the larvae is easy to observe during excursions. It is of considerable interest as a good example of tracheo-branchial breathing. Gills have the appearance of thin delicate plates that are placed in rows on both sides of the abdomen (Cloeon, Siphlurus). These gentle tracheal leaves continuously move, which can be perfectly seen in a larva sitting in the water even without the aid of a magnifying glass. Most often, these movements are uneven, jerky: as if a wave runs through the leaves, which then remain motionless for a while until a new wave. The physiological significance of this movement is completely understandable: in this way, the flow of water washing the gill plates increases, and the exchange of gases accelerates. The oxygen demand of the larvae is generally very high; therefore, in aquariums, the larvae die at the slightest damage to water.
The nutrition of the larvae is very diverse. Freely floating forms living in stagnant waters, which are most often found on excursions, are peaceful herbivorous animals, feeding on Microscopic green algae (Cloeon, Siphlurus). Other species lead a predatory lifestyle and actively hunt for small aquatic animals. The food of many species of mayflies is still not well understood.

Reproduction phenomena in mayflies are of great interest and have long attracted the attention of observers. Unfortunately, these phenomena on excursions have to be seen unless by chance. As mentioned above, females drop their eggs in water. Larvae hatch from the eggs, which grow and molt many times (Cloeon has more than 20 molts), and wing rudiments gradually form in them. When the larva finishes its development, the winged insect hatch. In this case, the larvae floats to the surface of the reservoir, the covers on its back burst, and in a few seconds an adult mayfly comes out of the skin, which flies up into the air. Since the hatching process is often carried out simultaneously in larvae, the surface of those reservoirs where the larvae are found in large numbers represents a remarkable sight during hatching, more than once described in the literature: the surface of the water boils from a lot of hatching insects, and clouds of mayflies, like flakes of snow flying in the air. However, winged insects that hatch from larvae do not represent the final stage of development. They are called subimago and after a short period of time (from several hours to 1-2 days) molt again, thus turning into imago (the only case among winged-shaped molting insects). Sometimes on an excursion you can watch how a winged mayfly sits on some plant or even on a person and immediately drops its skin.

Squad ticks;

hydrachnid family;

The vast majority of ticks are very small animals, not more than one millimeter, only a few are larger, for example, our tick.

CLASS Molluscs Dentist (Gastropoda)

In gastropods, the body consists of a head, trunk, and leg. The leg is the muscular abdominal part of the body, resting on which the mollusk slowly glides.

Most gastropods have a spiral twisted shell (therefore they are also called snails), in which the animal can completely hide. In the lower part of the shell there is a wide opening - the mouth, through which the mollusk protrudes its head and leg during movement. Some terrestrial gastropod mollusks - slugs - have no shells.

In the throat of gastropods there is a muscular tongue covered with spines - the so-called grater. Using it, the mollusk scrapes the tissue of plants or scrapes the plaque formed on underwater objects from various microorganisms.

Family Definition Table

1(4) The mouth of the conch, when the mollusk draws its head and leg in, is closed by a thin lid attached to the leg.
2(3) On the curls of the shell there are dark longitudinal stripes (they may be poorly visible due to plaque covering the shell), up to 45 mm;
3(2) Sink without dark stripes, one-color; value not more than 12 mm;
4(1) There is no lid at the mouth of the conch, so that the mollusk hidden in it shows the compressed sole of the foot.
5(6) The turns of the shell are twisted in one plane;
6(5) The shell is twisted conically.
7(8) The shell is twisted to the right (if you take the shell so that the top is directed away from you and the mouth towards you, then the mouth will be located to the right of the center line);
8(7) The shell is twisted to the left (the mouth is to the left of the center line); FAMILY (Lymnaeidae)

In the pond, the shell is twisted spirally, in several revolutions, in the form of a turret. In the USSR there are about 20 species.

Common pond (Lymnaea stagnalis) The largest of our ponds, the height of the shell is 45-55 mm, and in some individuals even up to 65 mm. It lives in stagnant water bodies - ponds, lakes, backwaters of rivers with abundant vegetation. Here you can see how the pond, sticking out his leg and head with tentacles from the sink, slowly glides over the plants. Having reached the surface of the water, the pond spreads its leg wider and slides, hanging from below to the surface film of water. At the same time, at the mouth of the shell, on the side of the leg, a round breathing hole can be seen. In mid-summer, the pond grows to the surface of the water 6-9 times per hour. Distributed in Europe and North Asia to Kamchatka.

Ear pond (Lymnaea auricularia) This mollusk has a shell with a very wide mouth, the height of the shell is 25–40 mm, and the width is 20–30 mm. It lives in the surf zone of stagnant water bodies. Distributed in Europe and Asia (except for the southeast).

COIL FAMILY (Plarmrbidae)

The coils of the shell coils are located in the same plane. Coils are not as mobile as ponds, and cannot be suspended from a surface film of water. In the USSR there are 35 types of coils.

Horn coil (Planorbarius corneus) This mollusk has a shell diameter of up to 35 mm. It lives on plants in stagnant bodies of water, in the same place as an ordinary pond, but rarely rises to the surface of the water. Distributed in Europe and Western Siberia to the Ob.

Edged coil (Ptanorbis planorbis) At the fringed coil, the shell is dark brown, with a diameter of 20 mm, with 5-6 revolutions. On the last turn below there is a sharp ledge - keel. It lives in shallow reservoirs and in the coastal part of large reservoirs. Distributed in Europe and Western Siberia to the Yenisei.

Spool (Anisus vortex) The shell is yellow, with a diameter of up to 10 mm, with 6-7 revolutions. At the last turn, a sharp, shifted downward keel. It lives in coastal thickets of standing reservoirs, often floats on the surface of the water. Distributed in Europe and Western Siberia to the Yenisei.

FISIDA FAMILY (Physidae)

The fizid has a turret-shaped shell, like that of a pond, but is twisted to the left.

Phiza bubbly (Physa fontinalis) The shell is dull, pale yellow, 10-12 mm high, 5-6 mm wide, the height of the mouth is more than half the height of the shell. It lives on vegetation in various ponds. Distributed in Europe and North Asia.

Aplexa sleepy (Aptexa hypnorum) The shell is shiny, golden brown, 10-15 mm high, 5-6 mm wide (mouth height less than half the height of the shell). It lives only in temporary, drying up reservoirs in the summer. Distributed in Europe, Western Siberia and the south of the Far East.

FAMILY PILLS (Viviparidae)

The mouth of the conch alone is closed by a lid. Sinks with dark longitudinal stripes. Luzhanka is also called viviparous, as they do not lay eggs, like other mollusks, but give birth to small, already having a shell meadow.

Marsh meadow (Viviparus contectus) Sink up to 43 mm high. It lives in lakes, ponds, sometimes even in puddles with clean water. Holds on the bottom. Distributed in Europe and Western Siberia to the Ob.

FAMILY BITINI (Bithyniidae)

As in the puddles, the shell mouth is closed by a lid at rest, but the shells are monochromatic, without stripes.

Bitinia tentacle (Bithynia tentaculata) Sink up to 12 mm high. It lives in standing and weakly flowing reservoirs, on stones, in silt and among plants. Distributed in Europe and Western Siberia.

Terrestrial gastropods

Terrestrial gastropods can be divided into two groups: snails with a shell, and slugs that have no shell (in some species, a small remainder of the shell is hidden under the skin and is not visible from the outside). Since the skin of the mollusks is bare, many species adhere to humid habitats. In addition, during the day, animals are usually motionless. In this case, the snails completely hide in the sink, sucking the sole of the foot to the substrate, and the slugs crawl under cover - stones, leaves, between lumps of soil. But at night, and in rainy times and during the day, mollusks crawl from place to place.

Snails

In land snails, the shell is spirally twisted. In some species, the shell is elongated, so that its height significantly exceeds the width, in other species, on the contrary, the shell is low and its width is greater than the height. During the movement, the mollusk protrudes its head and leg from the shell. On the head are visible 4 forward tentacles. At the ends of two longer tentacles there are dark balls - these are eyes. If you carefully touch the tentacles, the mollusk immediately draws them in, and if you disturb it strongly, it will completely hide in the sink. In the USSR, several hundred species of snails are found. Basically, these are very small, difficult to distinguish from each other species (often only by internal structure) We will consider only some of the largest and most widespread forms.

Amber (Succinea putris) It got its name for the amber-yellow color of an elongated, thin, fragile, almost transparent shell. The height of the sink is 16-22 mm, the width is 8-11 mm. Sink with 3-4 revolutions, the last revolution is strongly swollen and enlarged, the mouth is ovoid. Amber lives in moist places - in moist meadows, near water bodies, it can often be seen on the floating leaves of aquatic plants, and sometimes it even plunges into water. Widely distributed in the USSR.

Kohlikopa slippery (Cochticopa lubrica) This is a small snail, with a smooth shiny, elongated, conical shell, 6-7 mm high, 3 mm wide. It is very common in moist places - in meadows, in grass, in moss, in fallen leaves of moist forests. Distributed throughout the USSR.

Ifigen's bloated (Iphigena ventricosa) At this snail the shell is elongated, fusiform, ribbed, reddish-horny, 17-18 mm high, 4-4.5 mm wide, with 11-12 revolutions. A flat toothlike protrusion extends from the mouth above. It lives in forests, on litter, on mossy tree trunks. Distributed in the Baltic states and the middle zone of the European part of the USSR.

Rocky cohlodine (Cochlodina laminata) In this species, the shell is elongated, fusiform, slightly swollen, smooth, shiny, light-horny, 15-17 mm high, 4 mm wide, with 10-12 revolutions. At the mouth, two lamellar curved protrusions are visible. It lives in forests, on rocks, stumps, tree trunks. Distributed in the middle lane of the European part of the USSR, north to the Leningrad region, east to Kazan.

Shrub snail (Bradybaena fruticum) This snail has a spherical shell, almost smooth, 16-17 mm high, 18-20 mm wide, with 5-6 revolutions. Coloring can be different, from grayish-white to reddish-horn, often a narrow brown strip is visible on the last turn of the shell. It lives in shrubs, deciduous forests, gardens, often a shrubby snail can be found on nettles and coltsfoot. Sometimes it climbs quite high on bushes, tree trunks and fences. Distributed in the European part of the USSR, in the Crimea and in the North Caucasus.

Garden snail (Cepaea hortensis) At the garden snail, the shell is cubar-like, similar to the shell of a shrubby snail, 15-16 mm high, 19-21 mm wide, with 4-5 turns, dark spiral stripes are visible at all turns. It lives in sparse shrubs and forests, on stones, rocks. Distributed in the Baltics

Shaggy snail (Trichia hispida) In this small snail, the conch is covered with thin hairs (in older individuals, they may be worn out). Sink 5 mm high, 8–9 mm wide, grayish or reddish-brown in color, usually with a light stripe at the last revolution. It lives in shrubs, on the ground in forest litter, under stones, and fallen trees. Distributed in the forest zone of the European part of the USSR, up to the Leningrad and Perm regions. Often causes harm to native, fruit and berry crops and ornamental plants, scraping leaf tissue so that only longitudinal longitudinal veins remain from them.

SLIMA

In slugs, the body is naked, devoid of a shell. In a calm state, the slugs look like small mucous lumps, but when they move, their body is greatly stretched. Like snails, 4 tentacles directed forward are visible on the head. At the ends of two longer tentacles there are eyes. Behind the head, a short neck is visible, passing into the back. Immediately behind the neck, an oval thickening is visible on the back, as if another layer of skin were superimposed on top. This is the so-called mantle covering the respiratory organ - the lung. A rounded breathing hole is visible on the right side of the mantle. As the name shows, slugs produce a lot of mucus. It primarily protects the mollusks from drying out. In addition, mucus helps them slip. Creeping slug always leaves a noticeable shiny mucous mark. In the middle zone of the European part of the USSR 16 species of slugs live. Of these, we will consider the most common, widespread forms.

Definitive birth chart

1(2) The breathing hole is located in front of the right edge of the mantle. When moving, the end of the leg protrudes slightly from under the back;
2(1) The breathing hole is located at the back of the right edge of the mantle. The leg from under the back does not protrude when moving.
3(4) Large slugs, over 100 mm long.
4(3) The size of the slugs does not exceed 50 mm.
5(6) The mucus is yellow;
6(5) The mucus is colorless, with irritation of the mollusk - milky white; GENUS OF ARION (Arion)

The body is thick, massive. The mantle is oval, rounded in front and behind. A breathing hole in front of the right edge of the mantle. When moving, the end of the leg protrudes slightly from under the back.

Arion Brown (Arion subfuscus) Body length up to 80 mm. The mantle is about 1/3 of the body length. Coloring can be different, from brown to orange, often rusty. The middle of the back is usually darker. It lives in deciduous, mixed and coniferous forests, occasionally found in old parks and cemeteries. Favorite food - hat mushrooms, in which the slug eats large cavities. It can also feed on dead parts of plants and animal corpses. Distributed in the forest and forest-steppe zone of the European part of the USSR. In the Altai Territory, Eastern Siberia, the Amur basin and Primorsky Territory, the subspecies Arion brown Siberian (Arion subfuscus sib ire us) lives, which is distinguished by a one-color-black body color. In warm, damp summers, this slug causes damage to gardens and fields located next to the forest.

Arion striped (Arion fasciatus) Body length up to 50 mm. The mantle occupies about 1/3 of the body length. The color is light - cream or yellowish-ash, the middle of the back and mantle is slightly darker. On the sides are clearly delimited dark stripes. It occurs more often in cultural biotopes - gardens, fields, gardens, parks. Often causes significant damage to crops. Distributed in the northwestern and central regions of the European part of the USSR.

GENUS OF DEROCERASES (Deroceras)

Small slugs, rather slender and mobile. The skin is almost smooth, with weak grooves, without rough wrinkles. A breathing hole in the back of the right edge of the mantle. The mucus is colorless, with milky irritation milky white.

Mesh slug (Deroceras reticulatum) Body length 25-35 mm. The mantle occupies about half the length of the body. The color is mostly cream or light coffee, with dark spots forming a grid pattern, especially visible on the mantle and back. Head and neck are also covered with small spots; tentacles are blackish. It lives in open places, avoiding forests and shrubs, more often on clay soils - meadows, fields, gardens, landfills, and in cities - in parks and gardens. Of all slugs, the most dangerous crop pest. In the gardens, he eagerly attacks cabbage, eating large holes not only in the outer leaves, but also inside the head of cabbage. In rainy years, it damages the seedlings of winter crops. Widely distributed in the European part of the USSR.

Field Slime (Deroceras agreste) Body length 35-40 mm. The mantle occupies about 1/3 of the body length. Coloring from almost white to cream, without a dark pattern. It lives in open places - meadows, swamps, near roadside ditches, on forest edges, but, unlike mesh slug, avoids places with cultivated soil. Widely distributed throughout the USSR.

Smooth slug (Deroceras laeve) Body length up to 25 mm. The mantle occupies about half the length of the body. Coloring from reddish-brown to almost black, one-color. Very hygrophilous and cold-resistant. It lives in swamps, wet meadows, in damp forests, on the banks of small overgrown ponds - here it can be not only on soil and plants, but also on their underwater parts. Widely distributed throughout the USSR.

GENUS OF LIMACS (Limax)

Large slugs, more than 100 mm long. The color is spotty, sometimes the spots merge into dark stripes. The keel protrudes on the tail of the back. The body is wrinkled, wrinkles are long, convex, with deep grooves between them.

Black slug (Limax cinereoniger) Body length 150-200 mm. The mantle occupies about 1/4 of the body length. Coloring is black or dark gray, keel is light. Tentacles with black dots. It lives in deciduous and mixed forests, and can live in coniferous forests with good grass cover. It feeds mainly on mushrooms and lichens. Distributed in the Karelian Autonomous Soviet Socialist Republic, the Baltic States, Belarus, in the western and central regions of the RSFSR, east to Nizhny Novgorod.

Big slug (Limax maximus) Body length up to 130 mm. The mantle occupies about 1/3 of the body length. Coloring motley: on a yellowish, ash-gray or off-white background, 2-3 pairs of dark stripes or rows of dark spots. The tentacles are one-color, without dark dots. It lives in cities - in parks, gardens, greenhouses, vegetable stores, where it can be harmful. Distributed in the northwestern and central regions of the European part of the USSR.

GENUS OF MALACOLIMAX (Malacotimax)

Malacolimax tender (Matacolimax tenellus) Body length up to 50 mm. The mantle occupies about 1/3 of the body length. The color is one-color, often yellow, greenish or grayish-yellow, sometimes orange-yellow. The head and tentacles are black or dark brown. The mucus is yellow. It lives in deciduous forests, occasionally in conifers. It feeds on cap mushrooms and lichens. Distributed in the northwestern, western and central regions of the European part of the USSR.

CLASS Mollusk bivalves (Bivalvia)

In bivalve mollusks, the shell consists of two halves connected on the dorsal side by an elastic ligament. On the ventral side, the shell halves can slightly move apart, and the clam leg protrudes through the gap formed. When moving, the mollusk spreads with its foot, like a plow, silt or sand at the bottom, hooks its foot on the ground and pulls the body with the sink forward, again extends the leg forward, again pulls up and thus crawls along the bottom in small steps. Some bivalve mollusks do not move, but sit in one place, attached to the substrate with special adhesive threads. Bivalves have no heads, so there is no grater. They feed on small planktonic organisms, which are sucked together with water through a siphon hole located at the rear end of the body. All bivalves live in the water.

Dreissena River (Dreissena polymorpha) The shell of the river dreissen is greenish-yellow, with brown stripes, 30-50 mm long. The lower edge adjacent to the attachment site is flat, two lateral convex. It lives in rivers, lakes and reservoirs.

BARBAR FAMILY (Unionidae)

At the perovlitsa, the shell is elongated-oval. On each leaf the most convex, outstanding part is visible - the top. Concentrating around the apex, arcuate lines pass on each leaf. Some of these arcs are sharper, darker are annual arcs, from which you can approximately determine the age of the mollusk. There are 4 genera in the family. The most famous are barley and toothless.

CROWN BIRTH (Unio) The shell has a thick-walled shell, the tops of the flaps protrude upward. If you look at the sink from the end, then the place of fastening of the wings - the ligament - will be in the recess.

Barley ordinary (Unio pktorum) In ordinary pearl barley, the shell is long, narrow, up to 145 mm, with almost parallel dorsal and abdominal edges. Coloring in young individuals is yellow-green, in old ones it is greenish-brown. It lives in lakes and rivers, in places with a slowed flow, on sandy, not very silted ground. Distributed in the European part of the USSR, except for the north and northeast.

Swollen Barrier (Unio tumidus) In this species, the shell is shorter, up to 110 mm, with non-parallel edges. The habitats and distribution are the same as that of common barley.

KIND OF TOOTHLESS (Anadonta) The toothless have a thin-walled shell, the tops of the valves do not protrude much. If you look at the sink from the end, then the place of fastening of the wings is not deepened. Some species have a large keel on the upper edge of the leaf. The shape of the shell is very variable in individuals of the same species living in different bodies of water.

GENUS OF A PEA (Pisidium) At peas, the apex of the shell folds is shifted to the side, the shell is short-oval. The size of the peas does not exceed 11 mm.

Pea (Pisidium amnicum) The diameter of the shell of a river pea is 10-11 mm. It lives in the backwaters of rivers and lakes, on silty-sandy soil. Distributed in the European part of the USSR and in Siberia to the Lena.

Well, we got to the most controversial aquarium snail, namely the pond. I know that 99% of aquarists not only dislike them, but hate them with fierce hatred for gluttony and fertility. However, it is worth telling about the pond (or rather the pond).

Bit of biology

Prudoviks are a family of snails from the order Pulmonata, which, according to different classifications, includes from one (Lymnaea) to two (Aenigmomphiscola and Omphiscola) or several genera (Galba, Lymnaea, Myxas, Radix, Stagnicola), which differ mainly in the structure of the reproductive system. By appearance (by shells) representatives of these genera differ little from each other. In our review, we provide descriptions of the seven most common pond species in central Russia. To avoid confusion, we indicate their species names according to the traditional classification, according to which all the ponds belong to the same genus Lymnaea. However, the description of individual species provides information on modern views on their systematics, along with their new names.

All the ponds have a well-developed spiral twisted to the right (see how to determine the curl) for 2-7 turns of the sink (see photos and drawings). For different types of ponds, it has different sizes and shapes - from almost spherical to highly conical, with a more or less high curl, with a very expanded last turn. In the majority - light horn, horn, brownish-horn, brownish-brown or black-brown. Most often, it is thin-walled, translucent and more matte, tower-like or ear-shaped, the mantle almost does not leave the mouth.
The body of the pond is right-handed, thick, their head is wide, transversely trimmed; respiratory and genital opening on the right side. The internal bag is in the shape of a conical spiral. The tentacles are flat, triangular, short and wide. The leg is quite long, massive. The sole is elongated-oval. There is a short siphon formed due to the outer edge of the mantle.
The throat of the pond is a muscular bag that passes into the esophagus, then into the goiter and stomach; the latter consists of a bilobed muscular section and an elongated pyloric; a muscular stomach is characterized by a rough structure and contributes to the crushing of captured food; in the pyloric stomach and in the intestine emerging from it, food is digested; the anus opens at the mouth of the conch.

Observing the pond in the aquarium, you can see how he protrudes the front of the body from the sink and slowly glides along the walls of the glass. In this protruded part of the body, you can distinguish the head, clearly separated from the rest of the body by a neck interception, and the leg - a large muscular organ of movement of the pond, occupying the entire abdominal part of his body. On the head are triangular movable tentacles, at the base of which eyes sit; from the ventral side of the head in front of its mouth is placed a mouth gap. There are three types of pond movements: gliding on surfaces with the help of a leg, ascent and immersion due to the pulmonary cavity, and gliding from below on a surface water film.
The movement of the pond on the underwater surfaces can be well seen when it crawls along the glass wall of the aquarium. It is caused by muscular contractions that wave and uniformly run along the sole; these movements have a delicate adaptability, which allows the mollusk to move along the thin branches and leaves of aquatic plants.
Surfacing to the surface and sinking to the bottom by filling and emptying the pulmonary cavity. When the cavity expands, the snail floats to the surface without any push in a vertical line. For emergency immersion (for example, in case of danger), the pond puts out the air in the pulmonary cavity and drops sharply to the bottom. So, for example, if you prick the delicate body of a mollusk floating on the surface, then the leg will immediately be pulled into the sink, and air bubbles will burst out through the breathing hole - the pond will throw out all of its air ballast. After that, the mollusk will sink sharply to the bottom and will no longer be able to rise to the surface except by crawling along underwater surfaces due to the loss of its air float.
The third way of moving is to slide along the bottom surface of the water. When the pond ascends, the pond touches the sole of the foot of the surface tension film, then liberates mucus abundantly, spreads the leg, arching the sole slightly inward in the form of a boat and, reducing the muscles of the sole, glides over the surface tension film covered with a thin layer of mucus.

Like other pulmonary snails, ponds are devoid of primary gills and breathe atmospheric air with the help of the lung, a specialized section of the mantle cavity, to which a dense network of blood vessels adheres. In order to renew the air in the pulmonary cavity, they periodically rise to the surface of the water. Having risen to the surface, the pond opens its breathing hole, which is located on the side of the body, near the edge of the shell and air is drawn into the vast pulmonary cavity. At this time, you can hear a characteristic squelching sound - the "voice of the mollusk" - this opens the respiratory opening leading to the mantle cavity. In a calm state, the respiratory opening is closed by the muscular edge of the mantle.
The frequency of ascents for breathing depends on the temperature of the water. In well-heated water at a temperature of 18 ° -20 °, the ponds rise to the surface 7-9 times per hour. As the temperature of the water decreases, they begin to float to the surface less and less and in the fall, long before the water body freezes at a temperature of 6 ° -8 ° C, due to the general decrease in activity, they cease to rise to the surface altogether. While the photosynthesis of water plants continues, the ponds consume oxygen bubbles for plants to breathe, and then stop filling the mantle cavity with air. At the same time, it either falls off or fills with water - a paradoxical fact rare in nature when the same organ alternately functions as gills, then as light.
In addition to breathing air or water flowing in the lung cavity, the pond lives and due to skin respiration, which is performed by the entire body surface washed by water; cilia of the skin of the pond are of great importance, the continuous movement of which contributes to the change of water washing the surface of the body of the mollusk.

Prudoviks are omnivores, but in nature they prefer plant foods. Crawling slowly, they scrape off algae from various objects immersed in water, for example, from the surface of stems and leaves of higher aquatic plants. If algae becomes scarce, then they consume living plants - leaves and stems of aquatic plants, choosing the most tender of them, as well as plant detritus.
For scraping food, pond dwellers use a toothed grater - a horn plate, located in the throat on a tongue-shaped elevation. The grater plate from the surface is seated in rows of cloves. The nature of the grater's work is easy to observe in the aquarium, when the pond crawls on the glass and from time to time sticks the grater out of the mouth and runs it along the glass surface to scrape off the layer of green algae that has developed on it. Prudoviks sometimes use animal food - they devour the corpses of tadpoles, newts, fish and mollusks, scraping them from the surface, small invertebrate animals.
Lifestyle. At the height of summer, ponds stay near the surface of the reservoir, and sometimes on the surface of the water. For their fishing there is not even the need to use a landing net, they can easily be removed from underwater objects by hand.
When the ponds settled in ponds, such as small ponds, ditches and puddles, dry out, not all mollusks die. When adverse conditions occur, the mollusks secrete a dense film that closes the hole in the shell. Some can tolerate being out of the water for quite some time.

Prudoviki, like other pulmonary gastropods, hermaphrodites. Eggs and spermatozoa develop in the same organism, in different parts of the same gland, but after leaving the duct, the genital ducts separate, and the male and female genital openings at the mouth of the conch open separately.
A muscular copulative organ protrudes from the male genital pore during copulation; the female genital pore leads to an extensive receptor. Ponds mating is observed, with one individual playing the role of a female and the other male, or both mollusks mutually fertilize each other. Sometimes chains of copulating prudoviks are formed, with the extreme individuals playing the role of a female or male, and the middle ones of both.
Egg laying continues throughout the warm season, starting in early spring, and in the aquarium in the winter. Pond eggs in a suspended state are connected by a common mucous membrane. In an ordinary pond (Lymnaea stagnalis), the masonry looks like a transparent gelatinous sausage with rounded ends, which the mollusks lay on aquatic plants or other objects (video). In this species, the length of the roller reaches 45-55 mm with a width of 7-8 mm; The eggs in it are 110-120.
Large ponds are especially prolific. According to observations in the aquarium, one pair of ponds gave 68 clutches in 15 months, and in another 13 months - 168 clutches. The number of eggs in the clutch varies depending on the species.
After 20 days, tiny eggs come out of the eggs, already equipped with a shell, which grow quite quickly, eating plant foods.

Representatives of some species of pond fish that live in the deep lakes of Switzerland have adapted to live in great depths. Under these conditions, they are already unable to climb to the surface to capture atmospheric air, their pulmonary cavity is filled with water, and gas exchange occurs directly through it. This is only possible in clean, oxygen-rich water. Such mollusks, as a rule, are smaller than the fellow species living in shallow water.
- The shape of the shell of the common pond depends on the place of existence of a particular individual. These mollusks are extremely variable, varying not only their size, color, shape, but also the thickness of the shell.
- Seashells of all European species of ponds swirl to the right. Only as an exception are individuals with left-handed (leotropic) shells.
- The number of eggs in the clutch, as well as the size of the egg cord, varies widely. Sometimes in one clutch you can count up to 275 eggs.
- The pond is large quite demanding on the oxygen regime. At a high level of oxygen saturation (10–12 mg / L), mollusk populations are characterized by a high population density. Very rarely L. stagnalis was found in oxygen-deficient bodies of water.

Interestingly, the pond fish can breed, far from reaching their maximum age and size. For example, an ordinary pond swimmer becomes sexually mature at the end of the first year of his life, when he grows only half his normal size.
- Prudoviks can reproduce and being isolated from other individuals, so that copulation does not represent the act necessary for them to continue life, reproduction can very well occur through self-fertilization.
- Pond guns are used in neurophysiology as model objects for studying the functioning of the nervous system of animals. The fact is that nervous system prudovik includes giant neurons. Placed in a nutrient medium, isolated pond pond neurons are able to remain alive for several weeks. The location of giant neurons in the ganglia of the pond is quite stable. This allows you to identify individual neurons and study their individual properties, which vary significantly from cell to cell. The irritation in an experiment of a single ganglion cell can cause a complex sequence of coordinated animal movements. This may indicate that giant mollusk neurons are capable of carrying out functions that in other animals perform large complexly organized structures of many neurons.
- Snails lack hearing and voice, very poor eyesight, but the scent is perfectly developed - they are able to smell food at a distance of about two meters from themselves. Receptors are located on their horns.
- To improve digestion, the pond absorbs sand from the bottom of the pond
- Life expectancy: 3-4 years.
- The maximum crawl speed is 20 cm / min.
- The large pond (L. stagnalis), when the pond dries, releases a dense film that closes the hole in the sink. Some of the most adapted forms of mollusks tolerate being out of the water for quite some time. So, the common pond lives without water for up to two weeks.
- When freezing ponds, mollusks do not die, freezing in ice, and come to life when thawing.
- According to the results of recent joint research by scientists of the Tula Pedagogical University and the Institute for Development Biology of the Russian Academy of Sciences, new, very interesting Facts from the life of mollusks. As it turned out, snails have the ability to communicate with each other, transmit important information to each other, and even “give parental guidance” to larvae that have not yet been born, but are in suspended caviar. Although ordinary gastropod mollusks - the coil and big pond, scientists have the assumption that absolutely all representatives of the invertebrate world use a similar method of communication. At the first stage of the experiment, experimental ponds were divided into two groups. One of them was given food in normal amounts, and the second was completely devoid of food for three days. Then water samples were taken from the containers in which the mollusks were contained, and from each tank separately. As a result of the analysis, it was found that its chemical composition is significantly different from each other. Then, caviar, previously deposited by snails, was placed in both containers. In the third, control tank, caviar was also placed, but it was poured with clean water. All this was left for 10 days, after which the results were compared. As it turned out, in clean water, as well as in the one where full snails lived, the larvae managed to reach the stage of complete formation. The situation was completely different in that water where hungry snails lived - the development of larvae was almost completely inhibited. This fact was commented on by the doctor of biological sciences Elena Voronezhskaya, she said that the parents seemed to warn their children that they were in no hurry to develop and hatch, since they would have nothing to eat. In the course of further experiments, the following regularity was discovered: the longer the period of starvation of adult snails, the more they released a special substance into the water, which slowed down the development of larvae. This substance is called “RED-factor” from scientists. According to their assumptions, it is lipoprotein.
- At the pond most of the liver is located in the last turns of the spiral.
- Adapted to life in the hot springs near Lake Baikal, one of the forms of the pond - the elongated pond (Lymnaea peregra)
- Biologists drew attention to the large size and yellow-orange color. nerve cells brain of a large pond, well adapted to a polluted environment. These cells are stained with pigments known as carotenoids. They can accumulate oxygen and, if it is not enough in the environment, use the stored one.
- The blood of an ordinary pond is not red, like that of coils, but bluish, because it is stained with copper-containing hemocyanin.

So far, the issue was news on July 25, 18. Scientists at the Federal Research Center for the Integrated Study of the Arctic RAS (FITSKIA RAS) and the Northern Arctic Federal University (Arkhangelsk) have created a genetic catalog of pond mollusks. According to the ponds, their systematics was unclear, and we applied the molecular genetic method to the ponds of the Old World, examining material from about 40 countries. We conducted an audit, during which we showed that the ponds are subdivided into 10 genera, including a new genus for science and two species of ponds, discovered in remote areas of the Tibetan plateau. The genus is named Tibetoradix, and the species is Makhrov’s pond (Radixmakhrovi) and Kozlov’s Tibetan pond (Tibetoradixkozlovi) in honor of the prominent modern Russian ichthyologist Alexander Makhrov, as well as a traveler and explorer of Central and East asia Peter Kozlov, who lived in the XIX-XX centuries .. It turned out that in the countries of Europe, Asia and Africa, 35 species of pond dwellers live. "Previously, grades ranged from three, ten or more."

And as usual, for those who are too lazy to read

From early spring to late autumn, snails from a large pond family can be found in standing and slowly flowing water bodies. The common pond is the largest of them.

More than 100 species of this family are known, and we have several dozen species, most of which belong to the genus Prudoviks. The common pond, or lacustrine, is the most common and widespread in Africa, North America, Europe and North Asia to Kamchatka.

LIVING GLUTER

The appearance of the pond is very variable: depending on the conditions of existence, the color, shape and size of the shell and body vary. In this regard, several geographical subspecies are distinguished.

Prudoviks are ordinary inhabitants of ponds, lakes, backwaters of rivers, canals and other bodies of water with abundant vegetation. They live well even in brackish water. This is a big glutton, eating both living and rotting plants, and sometimes insects and fish eggs that have fallen into the water.

The mollusk spends most of its life crawling among thickets at a speed of 30 cm to 1 m per hour and scraping algae and small animals from the underside of leaves.

To do this, he has a special device in his mouth - a grater, or radula. It is a tongue with many sharp horn denticles. Sometimes ponds swallow sand, which, remaining in the stomach, helps digest food.

Ordinary ponds can be found in swamps and puddles with rather dirty water, although they do not live in rotting water. Snails can survive without water for up to two weeks if their pond is dry. In this case, they have mucus hardening in the air, which, like a lid, reliably seals a sink with a host drawn into it.

But the lakes, like some mollusks, have no real lids. Even after spending some time freezing in ice, after thawing, the pond can come to life.

UP FOOT

Once upon a time, the water ancestors of the pond dwellers breathed gills, and then went on land and acquired lungs, or rather, an unpaired lung - a respiratory cavity formed by a fold of skin. Later they returned to an aquatic lifestyle, but did not change their pulmonary respiration. From time to time, usually 6–9 times per hour, the ponds rise to the surface to renew air in the pulmonary cavity and expose the muscular edge of the mantle, rolled up into a tube, forming a breathing hole on the side, near the edge of the shell. But if necessary, the pond can not rise to the surface for quite a long time, about an hour, sparingly consuming air. Pulmonary respiration is partly replaced by cutaneous respiration. Having risen to swallow air, the snails slowly crawl along the underside of the surface film of water, leaving behind a mucous trail. This is possible due to the wide sole and the air-filled respiratory cavity. If you push such a snail, it, plunging into the water, rises again, like a float. But the mollusk can also compress the lung by releasing a bubble of air if it wants to dive deeper.

Snail Cradle

Like all gastropods, the common pond is hermaphrodite, that is, each individual has both female and male genital organs. But his fertilization is cross. To lay viable eggs, ponds mate from early spring to late fall, except in frosty winter monthswhich are carried out in a state of stupor at the bottom of the reservoir. Clad eggs in a double shell (from 20 to 130 pieces) are immersed in the mucous mass and suspended from the wall of the capsule or cocoon surrounding them. In general, this design looks like a transparent mucous cord attached to underwater objects. Each egg in such a string is protected and provided with protein material for the development of the embryo. Perhaps this way of taking care of the offspring came to the prudoviks from their land ancestors, who were important that the eggs did not dry out. After 20 days, small snails with a thin shell come out of the eggs, which grow quite quickly, eating plant foods, and at the end of the first year of life they are ready to become parents themselves, although they still reach only half their normal size.

Representatives of some pond species living in deep lakes have adapted to live at great depths. Under these conditions, they are already unable to rise to the surface to capture atmospheric air, their pulmonary cavity is filled with water, and gas exchange occurs directly through it. This is only possible in clean, oxygen-rich water. Such mollusks, as a rule, are smaller than the fellow species living in shallow water.

A BRIEF DESCRIPTION OF

Type: mollusks.
Class: gastropods.
Family: prudoviki.
Rod: prudoviki.
Species: common, or large, pond, or lake.
Latin name: Limnaea stagnalis .
Size: sink length - 68-70 mm, width - 27 mm.
Coloring: shell brown, brown, leg and body from blue-black to sand-yellow.
Pond life expectancy: on average about a year, up to 2 years.

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The big pond is a typical representative of freshwater. In our article we will consider the living conditions and typical features of the structure of this animal.

Mollusks: features of the organization

Translated from Latin, the name of this type of animal means "soft-bodied." Some of them have shells. But in any case, the body of these invertebrates is soft and non-segmented. You can meet them in fresh and salt ponds. For example, toothless and pearl barley live in ponds and lakes, and mussels and octopuses live in the seas. Snails and slugs can be found on wet land.

Three parts can be distinguished in the body of mollusks: head, trunk and leg. Most of them move quite slowly, since the muscles are represented by separate bundles. In all mollusks, the trunk is surrounded by a fold of skin called the mantle.

Classification Basics

Three classes of mollusks are distinguished depending on the structural features. Characteristic feature cephalopod is a modification of the legs into tentacles. They are located around the mouth. On the tentacles are suction cups, with the help of which animals catch and hold prey. Cephalopods are capable of reactive movement due to a special tubular formation - a funnel. Representatives of this class are squid, cuttlefish and octopus.

There are barley, zebra mussel, mussels and oysters. All of them have a body consisting of a trunk and legs, as well as a shell of two wings. The big pond is a representative of gastropods. Let us dwell on its structure in more detail.

Big Pond - representative of gastropods

Large, or found in fresh waters rich in vegetation. His body, like all gastropods, consists of a head, trunk and legs. The middle part is completely located inside a spiral-wound shell consisting of lime, covered with a layer of horn-like substance. This is a kind of home and shelter. The sink of a large pond is spirally twisted. Maximum count 4-5 revolutions. It has a hole called the mouth. Through it, the head and leg are pulled inward. The sink of a large pond and horn coil in case of danger is closed with a special lid. This structure is an additional defense against enemies.

The structure of a large pond

Why are the mollusks that the pond represents are gastropods? It's all about the structure of their body. There are no clear boundaries between its parts. The leg is a flat and muscular protrusion, completely occupying the abdominal part of the body. Its surface secretes mucus, which provides easy gliding on various substrates and water film.

On the pond there is a pair of tentacles. This If you touch them, the mollusk will pull its head into the sink. At the base of the tentacles are the eyes. Pond boats also have balance organs. They are represented by small bubbles, inside which are located special bodies. A change in the position of these structures preserves the balance of the mollusk.

Circulatory and respiratory systems

The big pond is of type. It consists of a two-chamber heart and vascular system. Blood mixes with abdominal fluid, washing all tissues and organs. From the heart, it enters the arteries, and in the opposite direction moves through the veins. Despite the fact that the large pond is living in water, it breathes exclusively atmospheric oxygen. For this, the animal moves to the surface of the water and opens out the breathing hole located at the edge of the shell. It leads to the lung, in which oxygen enriches the blood.

Digestive and excretory systems

The big pond is moving slowly but surely. Why would he constantly "travel"? The mollusk moves in search of food, scraping it from underwater objects with the help of a jaw and a grater. The latter consists of several rows of horn denticles. The process of breaking down nutrients is accelerated by the enzymes of the digestive glands - salivary and liver.

An anal hole opens above the head of the pond. And next to it, the duct of the urinary system opens. The latter is represented by a single kidney and ureter with a hole.

Reproduction and development

By the type of the reproductive system, the large pond is hermaphrodite. This means that both female and male germ cells are formed in his body. The fertilization of these mollusks is internal. As a result, there is an exchange of sperm. Mollusks place zygotes in gelatinous cords that attach to underwater objects. As a result, young individuals with a thin shell develop.

So, to summarize: the large pond is a representative of gastropod mollusks. These are typical inhabitants of fresh water bodies. The ponds have three parts of the body: the head, trunk and leg, as well as a spirally twisted shell.