Small pond fish. Subclass Pulmonata (Pulmonata) Shell shape of a large pond snail

Hello, Dear friends!

Pond snail (Limnaea)

Meet Limnaea or pond snail! A gastropod, native to Europe, Asia, and North America.

The main difference between the pond snail and some other species gastropods consists not only of appearance. The fact is that this mollusk breathes not with gills, but with lungs! Therefore, it can often be found on the surface of the aquarium.

The appearance of the pond snail is as follows: the snail has an elongated, rounded shell shape.

The top of the shell is pointed and has a right slope. Size of the mollusk: it grows up to 50 millimeters in height, and the total diameter of the shell is up to 28 millimeters. As you can see, friends, this is a rather large freshwater snail.

The pond snail also has eyes, which are located on the outside of its triangular, flat tentacles. The “leg” is relatively short, but quite wide. Basic color: the body of the mollusk itself is gray or grayish-green, and the shell is yellow, light yellow or dirty yellow. This snail is not picky about water quality!

As for food, the pond snail, like many species of gastropods, is omnivorous. It eats the remains of fish food and their waste products, and loves fallen parts that begin to rot. These snails are also scavengers and can utilize dead fish that have begun to decompose. There is only one “minus” about these mollusks - their insatiable, simply wild appetite! They are constantly eating! They love succulent plants, so keep this in mind, friends! Therefore, I highly recommend planting plants with hard leaves, such as pondweed, in the aquarium: these snails do not like hard plants.

As for the reproduction of pond snails, everything is somewhat simpler for them than for other species. The fact is that pond snails are hermaphrodite mollusks! At a certain period, these snails hang their eggs on the tips of plant leaves. Such icicle cocoons are quite easy to spot. Each cocoon contains up to hundreds of eggs. The entire clutch matures within 25-30 days.

Like this interesting snail! There is controversy over keeping pond snails in an aquarium. Some argue that this is an evil mollusk that, apart from trouble, brings nothing more to the aquarium. Others simply do not recommend placing it in an aquarium. In general, how many people - so many opinions! The main thing is to regulate their quantity and that’s it! Remove snail eggs from . Moreover, the time to detect the eggs of this snail is almost a whole month!

With this I say goodbye to you, dear friends! All the best to you and see you soon!

Gastropods are the most numerous and diverse group shellfish It has about 90,000 species living in the seas, fresh water oyomah, on land. Most of them have a one-piece shell.

One of the representatives of this class lives in lakes, ponds and river backwaters - a large pond snail about 5 cm in size.

External structure

In the pond snail, all three parts of the body are clearly visible: the head, the leg and the bag-like body. The top of the body is covered with a mantle. The pond snail has a spiral shell, twisted in 4-5 turns, which protects the body of the animal. The shell consists of lime, and is covered on top with a horn-like organic matter. Due to the spiral shape of the shell, the body of the pond snail is asymmetrical, since in the shell it is also curled into a spiral. The shell is connected to the body by a powerful muscle, the contraction of which pulls the animal inside the shell.

The pond snail's leg is well developed, muscular, and has a wide sole. The animal moves slowly by sliding over plants or soil due to the wave-like contraction of the leg muscles. Copious mucus discharge skin glands feet, facilitates smooth gliding.

Internal structure

Digestive system

In the mouth, on a special movable outgrowth resembling a tongue, there is a grater with horny teeth. With their help, the pond snail scrapes off the soft parts of plants and microscopic algae deposits on underwater objects. The pharynx contains salivary glands, the secretion of which processes food.

From the pharynx, food enters the stomach through the esophagus. The liver ducts flow into it. The stomach passes into the intestine, which makes several loops and ends with the anus at the anterior end of the body above the head.

Respiratory system

The body of the animal is covered on the outside with a mantle and is closely adjacent to inner surface shells. Part of the mantle forms a kind of lung; numerous blood vessels develop in its walls, and gas exchange occurs here. The pond snail breathes atmospheric oxygen, so it often rises to the surface of the water and opens a round breathing hole on the right at the base of the shell. Next to the lung is the heart.

Circulatory system

The circulatory system is not closed, the blood is colorless. The heart consists of two sections - the atrium and ventricle, and blood vessels. Blood flows not only through the vessels, but also in the cavities between organs. A large vessel departs from the heart - the aorta. It branches into arteries. The blood then enters the small cavities among connective tissue. There the blood gives up oxygen, is saturated with carbon dioxide, enters the veins and travels through them to the lungs.

Here the veins branch into numerous small vessels - capillaries. The blood is enriched with oxygen and gets rid of carbon dioxide. Blood rich in oxygen is called arterial, and blood poor in oxygen and rich in carbon dioxide is called venous. The blood then collects in the veins and enters the heart. It contracts 20-40 times per minute.

Excretory system

Due to the asymmetry of the body, the pond snail retains only the left kidney.

At one end, through a wide ciliated funnel, it communicates with the pericardial sac, where waste products accumulate, and at the other, it opens into the mantle cavity on the side of the anus.

Nervous system

The nervous system of mollusks is of the scattered-nodular type. It consists of five pairs of nerve ganglia (ganglia), interconnected by nerve bridges, and numerous nerves.

Due to the twisting of the body, the nerve bridges between some nodes form a cross.

Sense organs

The pond snail's head contains organs of touch - tentacles; there are also tactile cells in the skin. The pond snail has one pair of tentacles. There are eyes - they are located at the base of the tentacles. There are also organs of balance.

Reproduction. Development

Fertilization in the pond snail is internal. This animal is hermaphrodite. A single reproductive gland produces both sperm and eggs. They reproduce by eggs, which are laid on aquatic plants or other objects. Fertilized eggs are covered with a common mucous membrane and are securely attached to the substrate. Each animal lays about twenty clutches during the year.

After about twenty days, tiny animals emerge from the eggs. They grow quickly, eating plant foods.

The pond fish becomes sexually mature at the end of the first year of its life. It is also interesting that when the reservoir (in which pond snails live) dries out, not all mollusks die. Some secrete a dense film that closes the opening of the shell. In this state, a pond snail can live without water for about two weeks.

Names: common pond snail, marsh pond snail, large pond snail, lake pond snail.

Area: Europe Asia, North Africa, North America.

Description: pond snail, belongs to the pulmonary molluscs. The largest of the pond snails living in Russia.V last years divided into two types - Limnaea stagnalis And Limnaea fragilis The appearance of the pond snail is very variable: depending on the living conditions, the color, thickness, shape of the mouth and curl of the shell, and size vary. The pond snail's body can be divided into three main parts: the body, the head and the leg. The body follows the shape of the shell, fitting closely to it. The shell is thin spiral (twisted in 4-5 turns), highly elongated, with a large last whorl. The shell consists of lime, covered with a layer of greenish-brown horn-like substance. The head is large, with flat triangular tentacles and eyes sitting at the inner edge of their bases. The tentacles are thread-like. The pond snail's mouth leads to the pharynx. It houses a muscular tongue covered with teeth (grater). From the pharynx, food enters the stomach, then into the intestines. The liver helps digest food. The intestine opens through the anus into the mantle cavity. The leg is narrow and long, muscular, occupying the entire ventral side of the body. The breathing hole is protected by a prominent blade. The circulatory system is open. The heart pushes blood into the vessels. Large vessels branch into small ones, from which blood flows into the spaces between organs.

Color: The color of the legs and body ranges from blue-black to sandy yellow. The pond snail's shell is brown.

Size: shell height 35-45 mm, width 23-27 mm.

Lifespan: up to 2 years.

Habitat: standing bodies of water (ponds, lakes, river backwaters, canals, swamps) with abundant vegetation. It can live in slightly brackish water. The pond snail is also found in drying up reservoirs.

Enemies: fish.

Food/food: The pond snail feeds on rotting remains of plants and animals. It deliberately swallows sand, which remains in the stomach and helps grind hard food.

Behavior: the pond snail is almost always active. It crawls among the thickets, scraping algae and small animals from the underside of the leaves. Maximum speed crawling - 20 cm/min. Breathes air, the reserves of which are renewed by rising to the surface (6-9 times per hour). Pond fish, living in deep lakes at considerable depths, breathe air dissolved in water, which is filled in the respiratory cavity. When the reservoir dries, it seals the mouth of the shell with a thick film. It can freeze into ice and then come back to life when it thaws.

Reproduction: common pond snail- hermaphrodite. Cross fertilization. Lays eggs enclosed in transparent mucous cords, which it attaches to underwater plants and objects. Lays 20-130 eggs.

Breeding season/period: during the whole year.

Incubation: about 20 days.

Offspring: development without the larval stage. The eggs hatch into small pond snails with a thin shell.

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Pond snails are gastropods.

The largest of the domestic representatives of the pond snail family (Limnaeidae) - common pond snail (Limnaea stagnalis), having an elongated conical shell up to 55 mm high. U eared pond snail (L. auricularia) shell with a short curl, resembling an ear (height 26 mm). Marsh pond snail (L. palustris) similar to the common one, but its shell has the shape of a sharp cone with a small hole (shell height 32 mm). Sink egg-shaped pond snail (L. ovata) with a short whorl, and its last whorl with a wide ovoid opening (shell height 18 mm).

Pond fish live in freshwater bodies of water. The common pond snail is especially widespread. It stays near the surface of the water and is easy to catch. In the jar, it slowly crawls along the walls of the vessel. SlipperThis occurs due to the fact that the muscles of the sole of the wide leg contract in a wave-like manner.

Ponds: 1— ordinary; 2 - ear; 3 - swamp; 4 - ovoid

Pond snail structure: 1— oral lobes; 2— tentacles; 3— eyes; 4 - leg; 5— breathing hole

Pond snails can wander along the underside of the surface film of water, holding onto it with the help of their soles. At the same time, a ribbon of mucus remains behind them. It is believed that this movement is due to the surface tension of water.

The pond snail has air inside the respiratory cavity, which, like swim bladder in fish, supports it. If you give a slight push to a crawling snail, it will submerge in the water and float up again, like a cork. The cochlea can voluntarily compress the respiratory cavity and, due to a decrease in specific gravity sink to the bottom; when the cavity expands, it floats to the surface.

Pond fish are capable of staying underwater for very long for a long time. This is explained by the fact that the closed lungIn this cavity, air is used very rationally during breathing, and oxygen is gradually replaced by carbon dioxide. In addition, it is likely that respiration also occurs through the skin, using oxygen dissolved in water.

Pond snails feed on the leaves and stems of aquatic plants. Therefore, individuals large species cannot be planted in a decorative aquarium. In addition to plants, they eat small organisms (hydra, protozoa), fish eggs, meat and even the remains of dead fish and snails. So it is better to keep pond snails in a separate container.

When breeding, these snails lay eggs on aquatic plants and other objects. The masonry has the appearance of a transparent gelatinous sausage. In twenty daysThe eggs hatch into tiny snails, which, feeding on plant foods, grow quite quickly. This whole process can be observed in the aquarium.

All pond snails, like most gastropods, are hermaphrodites.

More interesting articles

Big pond snail - inhabitant of fresh water bodies. It has a cone-shaped, spirally twisted shell with 4-5 curls, a sharp apex and a large opening - the mouth. The shell serves as protection for the soft parts of the mollusk’s body; muscles are attached to it from the inside. The shell consists of lime covered with a layer of greenish-brown horn-like substance. In body pond snail three main parts can be distinguished: torso, head and leg, but there are no sharp boundaries between them. Through the mouth, the front part of the body and the leg protrude out. leg pond snail muscular. When wave-like muscle contractions run along its sole, the mollusk moves. Leg pond snail located on the ventral side of the body (hence the name of the class - gastropods).

The body follows the shape of the shell, closely adhering to its inner surface. On the outside it is covered with a fold of skin - the mantle. In front, the body meets the head. A mouth is placed on the underside of the head, and two sensitive tentacles are located on its sides. When touched, the mollusk quickly pulls its head and leg into the shell. There are eyes near the base of the tentacles on the head.

Features of life processes: Prudovik eats aquatic plants. In his throat is a muscular tongue covered with hard teeth. Prudovik From time to time it sticks out its tongue and scrapes it, like a grater, with the soft parts of plants, which it swallows. Through the pharynx and esophagus, food enters the stomach and then into the intestines. The intestine bends in a loop inside the body and ends near the edge of the mantle with the anus. Unlike all previously studied animals at pond snail There is a digestive gland, the liver, whose cells produce digestive juice. Thus, the digestive system pond snail more difficult than that of an earthworm.

Breathing is pulmonary. Periodically rising to the surface of the water, it fills the mantle cavity fresh air through a round breathing hole. The walls of the lung are densely intertwined with blood vessels; here the blood is enriched with oxygen and carbon dioxide is released. Within an hour, the mollusk rises to breathe 7-9 times. Next to the lung is the muscular heart, consisting of two chambers - the atrium and the ventricle. Their walls alternately contract (20-30 times per minute), pushing blood into the vessels. Large vessels turn into thin capillaries, from which blood flows into the space between the organs. Thus, unlike annelids circulatory system The mollusk is not closed, since it communicates with the body cavity and blood does not flow through the vessels all the time. From the body cavity, blood collects in a vessel that approaches the lung, is enriched with oxygen and enters the atrium. Blood pond snail colorless. The excretory organs are represented by one kidney. Main part nervous system pond snail constitutes a peripharyngeal cluster of nerve ganglia. Nerves extend from them to all organs of the mollusk.

Reproduction: Hermaphrodite. Postpones a large number of eggs enclosed in transparent mucous cords. Which are attached to underwater plants. The eggs hatch into small mollusks with a thin shell.