Large pond snail: characteristics, habitat, reproduction. Small pond snail Mollusk common pond snail

Pond snails are pulmonary mollusks. They are distributed throughout the world and live in fresh water bodies. People often have many questions about the structure and life functions of these representatives of the animal world.

general characteristics

Lakes and rivers are home to representatives of the class of gastropods, one of the most numerous and diverse groups in the world. The large pond snail reaches five centimeters and has a cone-shaped shell twisted into a spiral. Sink Not only serves as a home for the mollusk, it protects its soft parts. The shell is tightly connected to the muscles of the pond snail and consists of green lime. In the body of a pond snail, its main body parts, such as the head, torso and leg, are clearly visible.

Transitions from one part to another are completely devoid of sharp boundaries. The leg is the strongest part of the body of a mollusk. When a mollusk needs to move, it initiates wave-like muscle contractions along the leg, thereby being able to move unhindered along the bottom of the reservoir. The leg is located on the ventral side of the body. The large pond snail, whose shell completely follows the shape of the body, has a large head. There is a mouth on the lower part of the pond snail's head, and tentacles are visible on the side, which help the mollusk sense space. The animal also has eyes.

Digestive system of the pond snail

The large mollusk feeds on aquatic plants and small insects. It should be noted that the large pond snail is very voracious. Using its tongue, it gently scrapes off the top layer of the plant. Small cloves that look more like a grater help him in this. After the plant particles enter the pharynx and then the esophagus, they are sent to the mollusk’s stomach, where they are processed and go into the animal’s intestine. After some time, processed food is excreted through the anus.

Respiratory system of a pond snail

This type of mollusk has a round breathing hole, with the help of which the pond snail fills the lungs clean air. Often these animals rise to the surface of the water and swim slowly. You can see exactly how the mollusk breathes, because when it inhales, its respiratory opening is as open as possible. The presence of lungs confirms the fact that the ancestors of pond snails were land mollusks. The walls of the lung of a mollusk are tightly intertwined with vessels; in this place, the blood fills with oxygen and releases carbon dioxide.

The mollusk must often rise to the surface of the water to breathe, otherwise the animal may simply die. On average, a pond snail rises to the surface of the water 7 times per hour. Oddly enough, the mollusk has a two-chambered heart that contracts up to 30 times per minute. The heart disperses the pond snail's blood through the vessels. It should be noted that the mollusk has colorless blood. The nervous system is located in the pharynx area; it consists of special nerve nodes that give impulses throughout the mollusk’s body.

Pond snail behavior

The prudovik leads an active lifestyle. It constantly crawls among the thickets and scrapes off the top of the plants. The speed of the mollusk reaches 25 centimeters per minute. It never stops at one area of ​​water, but constantly moves around. Even after catching a pond snail while relaxing in nature, a person may notice the excessive activity of this animal.

Often aquarium lovers want to take a pond snail to their home and place it with other fish. But you need to remember that a pond snail caught in its natural environment and transferred to an aquarium with other fish can be dangerous. The fact is that we cannot rule out infections that the pond snail can infect the inhabitants of the aquarium; this can become a real tragedy for the owner. The first thing you need to pay attention to is the signs of a large pond snail and its behavior.

Reproduction of pond snails

The large pond snail is a bisexual creature, therefore, during mating, individuals engage in mutual fertilization. The genitals look like oblong cords and are attached to any underwater objects. The egg cell is covered with a double protective shell and is dressed in a cocoon.

The pond snail can lay a clutch containing about 300 eggs. But the number of eggs may vary. The most surprising thing is that, like the snail, the large pond snail does not have a developmental stage with a larva. The eggs hatch into a small pond snail with a thin shell. It is worth noting that not all pond snails become large individuals when they mature. It all depends on nutrition and external factors.

Not only large pond snails live in reservoirs, but also small ones. The small pond snail is a small snail that can be found in all water bodies of the country. They can be found in springs and puddles, posing a huge danger to humans. Such pond snails are carriers of flukes, and most often they are exterminated.

One more interesting view The mollusk is toothless. The large pond snail is very different from this species, but they can easily live in the same place. Toothless has a bivalve shell, which also consists of lime. The circulatory system of the mollusk is very similar to the pond snail.

Representative of the genus is also close to pond snails Mikas . It has a very fragile shell. They live in lakes and ponds. They reproduce at an incredible rate, but live only one season.

Among mollusks there are species that do not have shells at all, such as slugs.
All shellfish are an integral part food chain. So, mollusks eat small insects, but they themselves become food for fish.

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 has broken bilateral symmetry due to 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

In pond snails, like others pulmonary snails, lacking primary gills. They breathe using the lung, which is a specialized section of the mantle cavity, enriched big amount blood vessels. Ponds periodically rise to the surface of the water surface to fill their lungs 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. In pond snails it is not closed 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. Oral cavity 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).

Many different snails live in ponds, rivers, and gardens, but the most common species is the pond snail. It lives in places where there is sufficient moisture, so it can be seen all over the world. This mollusk is quite often stocked in aquariums, as it copes remarkably well with plaque that forms on glass, stones or other objects, and it is also interesting to watch such a snail.

The pond fish does an excellent job of removing the deposits that form on the glass of the aquarium.

Description of the mollusk

The pond snail is a freshwater snail that has a well-developed spiral shell. The shell itself consists of five or six turns. On one side it has an mouth, and on the other there is a sharp peak. It reliably protects the soft body of the snail from various adverse effects and mechanical damage.

The pond fish breathes with the help of its lungs, and therefore it is forced to periodically rise to the surface of the water. At the very edge of the shell there is a special round hole that leads into the lung. And it is there that the blood is enriched with oxygen and carbon dioxide is released.

The pond snail's body consists of three main parts:

• heads;
• torso;
• legs.

The leg of a freshwater inhabitant occupies the abdominal part of the body. It is muscular, and with its help the snail moves along the surface. The life cycle of mollusks is quite short, since they all die in winter. Depending on the species, pond snails differ from each other in the color of their shell, body and legs, and they may also have different shape and shell thickness.

The most common types

Snails are unique animals that do not bring any harm to humans; on the contrary, they have many benefits, since they actively eat various weeds, clean the aquarium well of growth, and even have healing properties. In nature, there are many variants of the pond snail, each of which has its own characteristic features.

But the most common types are:

There are other types of these mollusks, but they are much less common. For example, there are pond snails that live at a depth of up to 250 m or at an altitude of 5 thousand meters.

Nutrition and reproduction

The large pond snail feeds mainly on plant foods. In nature, it eats various weeds, algae and even rotten plants. In an aquarium using long tongue it scrapes off the plaque that forms on the walls. This mollusk also eats any food that settles on the bottom.

As additional feeding, you can put small pieces of eggshells and chalk into the aquarium. From plant foods, snails can be given apples, cabbage, zucchini, pumpkin, carrots, and lettuce.

In nature, the pond snail eats various weeds, algae and even rotten plants.

Pond snails, like many other snails , are hermaphrodites, but their fertilization occurs in a cross way. They are also able to independently fertilize their own eggs. These moisture lovers put off the a large number of eggs, which are enclosed in a special transparent mucous clutch. Usually it has an elongated shape and is attached to various underwater objects, most often to vegetation. Sometimes one such clutch contains up to 300 eggs.

The eggs themselves are small and almost transparent. After about a month, small snails hatch from them, which external signs no different from adults. Pond fish reproduce quite actively, so if they are in an aquarium, you need to periodically remove excess eggs. In captivity, these mollusks can live up to two years, and during this period they lay eggs up to 500 times.

Difficulties in maintenance and illness

Pond fish are completely unpretentious animals, but the main difficulty in keeping them is that they can carry dangerous diseases, which at first glance are almost impossible to recognize. The most common disease in these mollusks is fungal infection. And if an infected individual is placed in a common aquarium with fish and other inhabitants, it can quickly spread the infection.

To avoid such a situation, before placing the pond snail in a community aquarium, you need to keep it in quarantine for several days. During this period, you should put it daily for several minutes in a weak solution of potassium permanganate or table salt.

If the snail does not consume required quantity minerals and trace elements, then the walls of her shell may begin to become damaged or become thinner. In this case, the pond snail should begin to be fed with products that contain great content calcium. After some time, the shell will heal and be completely restored.

The shell is spirally twisted, without a lid. In some species (slugs) the shell is reduced. The ganglia are concentrated in the head region, forming the peripharyngeal nerve ring. A nerve branch extends from the right parietal ganglion to the accessory azygos ganglion. Pulmonary molluscs have one atrium, one lung and one kidney.

rice. 1.
A - top view, B - side view: 1 - mouth, 2 - cerebral ganglion, 3 - pleural ganglion,
4 - parietal ganglion, 5 - visceral ganglion, 6 - liver, 7 - pericardium, 8 - lung, 9 - heart, 10 - kidney, 11 - stomach, 12 - gonad, 13 - mantle cavity, 14 - leg, 15 - head, 16 - anus, 17 - additional azygos ganglion.

(Fig. 2) is one of the largest terrestrial mollusks in Europe. The spherical-twisted shell has 4-4.5 whorls, reaches a height of 5 cm, a width of 4.5 cm. The shell is usually yellowish-brown in color with dark brown stripes running along it. The color and width of the stripes vary. On the head of a grape snail there are two pairs of tentacles, one of which contains eyes, the other serves as organs of smell and touch. It feeds on green parts of plants. By eating grapevine leaves and buds, it can cause harm to vineyards.

rice. 2. Grape
snail (Helix pomatia).

The grape snail is a bisexual animal. It has one hermaphrodite gland in which female and male gametes are formed. A hermaphroditic duct departs from the gland, into which the albuminous gland flows. After the confluence of the protein gland, the hermaphroditic duct expands, forming two gutters: a wide one for eggs and a narrow one for sperm. Next, each of the gutters is transformed into independent channels, respectively, the oviduct and the vas deferens. The oviduct drains into the uterus, the uterus into the vagina. In addition to the oviduct, the ducts of the spermatic receptacle and bags with calcareous needles flow into the uterus. The vagina opens with the genital opening in a special skin invagination - the genital atrium. The vas deferens passes into the ejaculatory canal, which penetrates the copulatory organ, which opens into the genital atrium. During mating, grape snails exchange spermatophores (packets of sperm), which are captured by the spermatheca. Fertilization will occur after mating. Eggs that enter the uterus are fertilized by foreign sperm coming from the spermatic receptacle. The formed eggs are laid in a burrow, which the parent first digs in the soil with its muscular leg.

In a number of European countries, grape snails are used as food.

rice. 3. Big
pond snail (Limnea stagnalis).

(Fig. 3) and small pond snail (L. truncatula)- frequently encountered inhabitants of our fresh water bodies. The head bears one pair of tentacles, at the base of which there are eyes. Hermaphrodites. During mating, just like in a snail, sperm are exchanged and eggs are fertilized by foreign sperm. They lay eggs in slimy cords that are attached to underwater plants and other objects. Development is direct, without a larval stage. They breathe atmospheric oxygen, so they periodically rise to the surface of the water in order to take in a portion of air.

The size of the shell, its shape, the color of the leg and body are characterized by strong variability in the large pond snail. For example, the color of the body and legs can vary from blue-black to sandy yellow. The length of the shell of a large pond snail can reach 7 cm. The large pond snail is omnivorous, feeding not only on plants and small animals, but can eat dead plant debris and animal corpses.

rice. 4.
A - Arion rufus,
B - limax maximus
(Limax maximus).

A collective group of terrestrial pulmonary mollusks with a partially or completely reduced shell (Fig. 4). On the head, next to the mouth opening, there is a pair of labial tentacles, and on top there are ocular tentacles bearing eyes. The narrowed portion of the body between the head and mantle is called the “neck.” At the bottom of the neck, a gland duct opens that secretes mucus. In addition to this gland, numerous mucous glands are scattered throughout the surface of the body, so the entire body of the slug is covered with mucus. The main purpose of mucus is to moisturize the skin. On the right side of the neck is the genital opening. The mantle looks like a flat thickening on the dorsal side of the body. Near the right edge of the mantle there is a respiratory opening leading to the pulmonary cavity. Near the respiratory opening on the right edge of the mantle, the anus and excretory pore open. Slugs are bisexual animals. During mating there is an exchange male gametes. Eggs are laid in moist, shaded areas.

Most slugs feed on plants, lichens or fungi. Predatory slugs feed on oligochaetes or other types of mollusks. Active at night, stay hidden during the day. Slugs settling in areas occupied by agricultural crops can cause significant damage to crop plantings. For example, the field slug (Agrolimax agrestis) eats sown grains and seedlings of winter wheat and rye, and the netted slug (Deroceras reticulatum) causes great damage to the harvest of tomatoes and cabbage.

Description of classes, subclasses and orders of the Mollusc type:

• Class Gastropoda

  • Subclass Pulmonary (Pulmonata)

The habitat of Lymnaea stagnalis is very extensive - water bodies of North Africa and North America, Asia, 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 a brown color, which sometimes reaches 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 breathe 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.

The Prudovik snail feeds on both 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 are not averse to 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.