Features of the structure of the pond snail. Pond snails: description of freshwater mollusks. Type of circulatory system in the pond snail

The habitat of Lymnaea stagnalis is very extensive - water bodies of North Africa and North America, Asia, and Europe.

The Common Prudovik snail is able to live both in fast streams and in swamps, but it feels best in the coastal part of lakes. The pond snail actively crawls along the bottom of the reservoir and coastal vegetation, and sometimes comes out onto wet meadows.

The main difference between this one is that its eyes are located at the base of the antennae.

The Prudovik shell has Brown color, which sometimes goes dark. The base of the shell is quite fragile, the number of curls varies between 4-5, the dimensions of the shell are up to 55mm in height and up to 30mm in width. Lymnaea stagnalis are able to move vertically (by secreting a path of mucus, they crawl along it in all directions).

Snails breathing atmospheric air using the lung (a special part of the mantle cavity). To renew the air in the pulmonary cavity, the mollusks rise to the surface of the water and breathe using the edge of the mantle rolled into a tube.

In water rich in oxygen, pond snails are able to live at depth without rising to the surface. In this case, the lung is filled with water, through which gas exchange occurs.

How does the Prudovik snail feed? plant foods, and small insects and microorganisms. Quite often you can see snails eating the foliage of aquatic and coastal plants. If the number of mollusks in a reservoir increases greatly, this is very harmful to the surrounding plants.

In the aquarium, the Common Prudovik can be fed with cabbage stalks, lettuce or raw potatoes.

Many freshwater inhabitants don’t mind eating this snail, as well as its caviar.

Reproduction

By nature, Lymnaea stagnalis are hermaphrodites, so the eggs are fertilized both by their reproductive products and by other snails.

at one time the snail lays a large number of eggs enclosed in transparent mucous clutches.

In an aquarium, breeding of the pond snail is difficult, since most of the eggs laid are eaten.

The Prudovik snail reaches sexual maturity when its shell grows to 20 mm in length.

The pond snail family includes well-known freshwater lung mollusks that are widespread throughout the world.

Of the large number of species belonging to this family, the most famous for its large size is the common pond snail, the largest specimens of which reach 7 centimeters. From early spring to late autumn, you can observe these snails in ponds, river backwaters, and small lakes. It is interesting to watch how these bulky snails crawl along aquatic plants or along the bottom of a reservoir. There are especially many of them in mid-summer among the floating leaves of egg capsules or water lilies.

Pond snails are omnivorous, therefore, crawling along leaves and stems aquatic plants, scrape off algae from them with a radula, and at the same time absorb small animals that come across them on the way. The pond fish is one of the most voracious inhabitants of fresh waters. It eats not only plants and animals, but also corpses.

You can often see how a pond snail rises to the surface of the water and hangs from below with the wide sole of its foot, due to surface tension The water film slides slowly and smoothly in this position. It is not in vain that pond snails rise to the surface of the water. Even though they are aquatic organisms, but, like all pulmonary mollusks, they breathe with the help of the lung and are forced to rise to the surface to “sip” air. The respiratory opening of the pond snail, leading to the pulmonary cavity, is wide open. The presence of lungs in pond snails indicates that these animals originated from land mollusks and have returned to living in water for the second time.

Reproduction of pond snails

When mating, pond snails mutually fertilize each other, since, like all pulmonate mollusks, they are bisexual creatures. Snail eggs are laid in the form of long, gelatinous, transparent cords, which are glued to various underwater objects. Sometimes the eggs even stick to the shell of another individual of the same species. Pond snail eggs are a complex formation, since the egg cell is immersed in a mass of protein and covered on top with a double shell. The eggs, in turn, are immersed in a mucous mass, which is covered with a special capsule, or cocoon. A cord extends from the inner wall of the cocoon, attached at the other end to the outer shell of the egg, as a result of which it appears as if suspended from the wall of the cocoon. The complex structure of the egg clutch is also characteristic of other freshwater pulmonate mollusks. Thanks to these devices, the egg is provided with nutritious material and protected by strong shells. Inside these shells, pond snails develop without the stage of free-swimming larvae. It is likely that such protective devices of pond snail eggs were inherited from their land ancestors, where these devices had higher value than when living in water.

The number of eggs in a clutch varies quite widely, as does the size of the entire clutch - the mucus cord. Sometimes you can count up to 270 eggs in one cocoon.

Pond snails are characterized by extreme variability, and the size of the mollusks, the shape of the shell and its thickness, and the color of the legs and body vary greatly. Along with major representatives almost dwarf forms are known, undergrown due to unfavorable conditions and malnutrition. Some pond snails have a shell with thick, hard walls; there are also forms with an extremely thin and fragile shell that breaks at the slightest pressure. The shape of the mouth and whorl is highly variable. The color of the legs and body of the mollusk varies from blue-black to sandy yellow.

This “propensity” for variability played a big role in the evolution of pond snails. Within species arose big number local varieties that differ in the listed characteristics, and it is often very difficult to determine whether this is a geographical subspecies or a variation due to specific living conditions in a given body of water.

Species of pond snails

Along with the common pond snail, a permanent inhabitant of our inland waters, there is another, also extremely variable species - the long-eared pond snail. In addition, the ovoid pond snail, marsh pond snail and some others live in stagnant reservoirs.

It's interesting that in deep-sea lakes In Switzerland, pond snails have been discovered living at considerable depths. At the same time, they are no longer able to rise to the surface to breathe air and have developed another adaptation. The pulmonary cavity of these snails is filled with water, and they breathe oxygen dissolved in water. The absence of gills in pond snails, in contrast to primarily aquatic mollusks, again proves their origin from land snails.

The only representative of our fauna from the genus Myxas is close to pond snails, differing from them in a very thin and fragile shell, almost completely covered with a mantle. Thus, the shell of this mollusk turned from external to internal. These snails live mainly in floodplain ponds and lakes, where they sometimes breed in huge numbers. However, in mid-summer the snails disappear because they life cycle ends in one season.

Common pondweed– lat. Limnaea stagnalis, a representative of the phylum mollusks, belongs to the class Gastropods. A feature of the common pond snail, like all representatives of the pond snail family, is its peculiar swimming in water. A special organ (leg) is directed upward during movement, protruding slightly on the surface of the water. To prevent the common pond snail from drowning while moving, the middle of the leg bends down, thus acquiring the shape of a boat, while the animal’s shell is directed down to the bottom. Scientists do not yet understand this peculiar movement.

Structure

The snail's eyes are located at the base of the second pair of tentacles. The common pond snail breathes through one lung, which is a modified mantle cavity. The air in the lungs, in a calm state of the mollusk, prevents it from falling to the bottom. But if at this time you touch an ordinary pond snail, it instantly releases air from the respiratory tract and instantly falls down. It also has one kidney and one atrium. The shell of the common pond snail has the shape of a twisted spiral.

Animal characteristics:

Dimensions: clam length 5 – 7 cm.

Color: The common pond snail has variable colors, from dark blue to yellow flowers. The shell has a thin translucent structure.

Food and habitat

Common pond snails They are omnivorous animals, they can eat both plant and animal foods, mainly algae, aquatic plants, uruti leaves, etc. Common pond snails are widely distributed throughout to the globe, mainly on ponds, rivers, lakes, etc. They live at shallow depths.

Every beginner in the aquarium business after a while is faced with the fact that the water becomes cloudy and aquatic plants begin to grow uncontrollably. Cleaning an aquarium and putting it in order takes a considerable amount of time. But you can have assistants - one of them is a pond snail. She is a natural cleaner of walls and aquarium accessories. In addition, snails are no less interesting to watch than fish.

Appearance and structure of the pond snail

Lymnaeidae is the Latin name for the pond snail. They live in fresh stagnant water or in reservoirs with slow flow.

The common pond snail has a fine-spiral shell with 5-6 curls, usually twisted to the right. Species with left-handed shells are found only in New Zealand and the Sandwich Islands. The degree of its elongation depends on the current in a given body of water - the width can be 0.3-3.5 cm, the height is from 1 to 6 cm. There is a large hole in the shell on the front side.

The color of the pond snail depends on natural features habitats. Most often, sinks are in a brown palette. And the head and body are from yellowish-brown to bluish-black.

The body of a mollusk consists of three sections - head, trunk and legs. All these parts are tightly attached to the inner surface of the shell. The snail's head is large, there are flat triangular tentacles on the head, with inside there are eyes.

The mollusk breathes through an opening protected by a noticeably protruding blade.

Habitats

The water snail pond snail is found in Europe, Asia, North America And North Africa. In addition to fresh standing waters and slow-flowing reservoirs, they are found in slightly salty and salty waters, as well as in geysers. In Tibet they live at an altitude of 5.5 thousand meters and a depth of 250 meters.

Varieties of pond snail

The species differ in the shell color characteristic of each locality, the thickness of its walls, the shape of the rings and mouth, the color of the legs and body.

Common pond snail (or large pond snail) is the most common species in the family gastropods. The length of the shell, which has a conical shape, is 4.5-6 cm, its width is 2-3.5 cm. The spiral of the shell has 4-5 rings, which expand significantly with each revolution, ending with an impressive size hole. The color of the semi-translucent walls is brown. The body has a greenish-brown tint. This type Ubiquitously inhabits freshwater bodies of the countries of the Northern Hemisphere.

The small pond snail (also called the truncated pond snail) has an elongated, pointed shell with 6-7 whorls. The turns of the rings are twisted to the right. The walls of the shell are thin but strong, whitish-yellow, almost transparent. It is 1-1.2 cm long, 0.3-0.5 cm wide. The body color is white-gray, uniform, but dark spots are possible on the mantle. This species is widespread in the nature of Russia, inhabiting swampy reservoirs and ponds. Sometimes found at low water levels in drying up reservoirs.

In the auricular species, the opening of the shell resembles a human ear - hence the name of this species. The shell is from 2.5 to 3.5 cm in height, 2.5 cm in width. Its walls are thin, the color is gray-yellow. This mollusk has no more than 4 shell rings. The shell has an almost round appearance, since the last whorl is quite large diameter. The body is yellowish-green and grayish-green with many specks. The mantle is gray or spotted. Found in bodies of water with different water compositions. Lives on rocks, sunken tree trunks, stems and leaves of aquatic plants.

Other known species pond snail:

• frilled (cloaked);
• oval (ovoid);
• swampy

Habits in the wild and life expectancy

IN natural environment Pond snails feed mainly on plants. But sometimes they eat flies, fish eggs and other similar small aquatic life.

To breathe, they climb out from the water column to the very surface. A snail needs to rise at least 6-9 times a day. But for species that live at considerable depths, oxygen dissolved in water is sufficient. The mollusk takes water into the lung cavity, turns over in the water with its sole up and slightly pulls it into the shell.

In nature, a pond snail can rarely be found sitting motionless on some snag. The mollusk is almost constantly busy - scraping algae from stones and eating aquatic vegetation. pond snail is about 20 cm/min.

Although most Pond snails spend their lives in the water column; they survive well in dry reservoirs and in water covered with a crust of ice. The mollusk simply seals the shell with a film, and when moisture appears or thaws, it comes to life.

On average, under conditions wildlife The lifespan of a pond snail is only about 9 months. But with proper maintenance, a pond snail in an aquarium can live up to 2 years.

Aquarium content

The pond snail is a voracious mollusk. Therefore, it is better not to place them in carefully grown luxurious home “herbal gardens” - you may lose all aquatic plants. Snails especially like soft plants with succulent stems and leaves. But the pond snail is unpretentious in its maintenance.

Basic conditions:

• Water temperature in the aquarium should be maintained at 20-26°C. In more warm water the mollusk will begin to actively reproduce, which is undesirable in a small volume of water.
• Hardness of water – moderate, lighting – dim (optimally – low-power fluorescent lamp).
• Aquarium volume Any will do, the main thing is to control the population, not allowing pond snails to multiply endlessly. If there are too many individuals, diseases may develop.
• you need a rocky one - pebbles are best, but a coarse sandy bottom is also acceptable.
• Clean the aquarium with pond snails as usual, replacing a third of the water every 7 days. Filter You will need a powerful one, the direction of the jet is preferably horizontal.

Before introducing new pond snails, they must be kept in quarantine for several days. It is recommended to buy shellfish from pet stores. Since in the markets, snails can be freshly caught in a pond, and infect the entire aquarium with infections.

Who can you put in the same aquarium with?

Feeding at home

Pond fish prefer plant foods. They do not require frequent additional feeding - algae, rotten parts of plants and fish waste are sufficient for nutrition. The mollusks, like a grater, scrape off all these remains from the walls and soil with long, powerful tongues. You can also give them:

• fresh pumpkin,
• apples,
• zucchini,
• white cabbage,
• broccoli,
• tomatoes,
• carrot,
• greens grown at the dacha (all cut into small pieces).

From time to time, pond snails need mineral feeding - calcium is needed for shells. It is found in chalk, egg shells, sepia - all this must be given in crushed form.

Breeding

Pond fish are hermaphrodites. They reproduce either singly or in flocks. Eggs are laid several times throughout the year. That is, during a lifetime they hatch offspring from about 500 clutches. Clutches of eggs are attached to plant leaves.

The clutch consists of small transparent eggs fastened together with mucus, forming an oval-shaped sac. If favorable conditions contribute to this, one individual makes up to 25 clutches of 80 eggs within 4 months.

The incubation period is 14-20 days. Newly hatched babies already have thin shells.

Sexual maturity in pond snails occurs at approximately 7 months.

Diseases

These snails are resistant to disease, but they themselves are often carriers of infection (which is practically undetectable by eye). They themselves suffer from fungus - visually this manifests itself in the form white plaque on the sink. Therapy - regular baths with manganese and saline solutions, long-term quarantine.

How much does a pond snail cost?

To avoid infections, it is better to purchase pond snails from specialized pet stores, rather than from private owners, and not to catch them yourself in water bodies. average cost one adult – about 50 rubles.

Contact Hazard

Pond snails (Lymnaea stagnalis) belong to the class Gastropods, the subclass of true snails and the order Pulmonata. Currently there are about 120 species. The pond snail and other species of this family are very variable: the configuration, size, thickness of the shell, and the color of the legs and body of these organisms vary. They live in fresh water rivers, lakes and ponds. Ponds are equipped with a solid shell with a sharp top, twisted in 4 - 5 turns, and a large mouth from which the head and leg protrude. The head is equipped with a mouth, two tentacles and two eyes. The pond snail's body is a large spiral sac covered with a mantle and shell, located above the leg. The pond snail is disturbed bilateral symmetry, caused by the turbo-spiral shape of the shell, which led to asymmetry of the organs located in the mantle cavity (one atrium, one kidney, half of the liver). On the ventral side of the pond snail there is a massive muscular leg with a wide sole, which serves for its movement.

Structure

Pond snails, like other pulmonate snails, lack primary gills. They breathe using the lung, which is a specialized section of the mantle cavity, enriched big amount blood vessels. Pond snails periodically rise to the surface of the water surface to fill their lungs with atmospheric air through a round breathing hole located at the base of the shell, since they can stay under water for no more than an hour. In addition, pond snails are able to breathe over the entire surface of their body. In clean reservoirs, in water enriched with oxygen, mollusks can live at depth and not rise for a new portion of oxygen. They get oxygen from the water that fills the lung, which functions like a gill. Living in such conditions, mollusks are smaller than those living in shallow water. The heart is located next to the lung and consists of an atrium and a ventricle. Pond snails have an open circulatory system with colorless blood. One kidney serves as the excretory organ.

The nervous system is a peripharyngeal nerve ring formed by nerve ganglia, from which nerves extend to all organs. The tentacles are equipped with tactile receptors and chemical sense organs (taste and smell). There are also balance organs.

The pond snail's digestive system consists of the esophagus, pouch-shaped stomach, liver, intestines and ends at the anus. The oral cavity of the pond snail passes into a muscular pharynx, in which there is a grater tongue (radula), covered with rows of hard teeth. The radula pond snail scrapes off particles of plants and small animals and eats them.

Pond snails feed mainly on plant foods. Their diet includes both living plants and decomposed ones. In addition, they eat bacteria and animal food (flies caught in the water, fish eggs).