In Russia and Europe there are different types of pond snails. Among them, the largest is the common pond snail, the shell of which can reach 7 centimeters. All species breathe with lungs, therefore, from time to time they are forced to swim to the surface. You can often observe how the pond snail, the photo of which is presented in this article, smoothly and slowly slides along the lower part of the surface film of water, picking up oxygen from the air.
If the molluscs “suspended” in this way are somehow disturbed, they immediately release an air bubble from the respiratory hole and fall like a stone to the bottom. The eared pond snail is the closest relative of the common one. Its shell reaches 2.5 centimeters, which depends on the abundance of food and the temperature in its reservoir.
The common pond snail and other species of its family (except for the above, in our reservoirs you can find egg-shaped, small and marsh) are very variable. At the same time, the shapes, sizes, shell thickness, color of the body and legs of snails vary. Along with those that have a strong shell, there are species with a veryfragile, thin shell that breaks even with the slightest pressure. There can also be various forms of a curl and mouth. The color of the body and legs varies from sandy yellow to blue-black.
Building
The body of the mollusk is enclosed in a spirally twisted shell, which has an mouth (a large hole) and a sharp top. The shell of the common pond snail is covered with a lime layer of a horn-like greenish-brown substance. She is a reliable protection for his soft body.
In the body of a snail, 3 main parts can be distinguished: the leg, head and torso - although there are no sharp boundaries between them. Only the front part of the body, leg and head can protrude from the shell through the mouth. The leg is very muscular. It occupies the abdominal part of the body. Such snails are called gastropods. At the same time, sliding on objects with the sole of the foot or hanging to the bottom film of water, the mollusk smoothly moves forward.
The body at the same time copies the shape of the shell, adjoining it very closely. It is covered in the front part by a mantle (a special fold). The space between it and the body is called the mantle cavity. The torso in front passes into the head, which has a mouth on the underside, and two sensitive tentacles on the sides. A pond snail, when lightly touched, instantly draws its leg and head into the shell. Near the bases of the tentacles, one eye is located.
Circulation
The ordinary pond snail has enough structureinteresting. So, he has a heart, which pushes the blood into the vessels. In this case, large vessels are subdivided into small ones. And from them already the blood goes into the gaps between the organs. Such a system is called "unclosed". Interestingly, the blood washes each of the organs. Then she again gathers in the vessels that lead to the lung, after which she goes directly to the heart. In such a system, it is much more difficult to ensure the movement of blood than in a closed system, since it slows down between organs.
Breathing
Despite the fact that the snail lives in water, it breathes atmospheric air. To do this, the common pond snail, the structure of which is described in this article, floats to the surface of the reservoir and opens a round breathing hole at the edge of the shell. It leads to the lung, a special pocket in the mantle. The walls of the lung are densely woven with blood vessels. In this place, carbon dioxide is released and the blood is enriched with oxygen.
Nervous system
This mollusk has a near-pharyngeal concentration of nerve nodes. From them, the nerves go to all organs.
Food
The snail's mouth leads to the throat. There is a muscular tongue covered with teeth ─ the so-called grater. The common pond snail, the photo of which can be seen in this article, scrapes off plaque from all kinds of microorganisms that form on various underwater objects, and also rubs various parts of plants. Food from the pharynx goes to the stomach, and then tointestines. The liver also aids in its digestion. In this case, the intestine opens with an anus into the cavity of the mantle.
Movements
If you put a caught pond snail in a jar, it immediately begins to actively crawl along its walls. At the same time, a wide leg extends from the shell opening, which serves for crawling, as well as a head with two long tentacles. By sticking the sole of the foot to various objects, the snail glides forward. In this case, sliding is achieved by wave-like, smooth contractions of the muscles, which can be easily observed through the glass of the vessel. Interestingly, the common pond snail can wander along the lower surface of the water, as we have already discussed above. At the same time, it leaves a thin tape of mucus. It stretches across the surface of the water. It is believed that snails moving in this way use the surface tension of the liquid, hanging from below to the elastic film that forms on the surface due to this tension.
Such crawling can be easily observed on the calm surface of the reservoir, going on an excursion or relaxing in nature.
If a pond snail, crawling in this way, under a little pressure again plunges into the water, it will be seen how it again, like a cork, rises to the surface. This phenomenon is easily explained: there is air inside the respiratory cavity. It supports the snail like a swim bladder. The pond snail can compress its respiratory cavity arbitrarily. In this case, the mollusk becomes heavier, therefore, sinks to the very bottom. But atexpanding the cavity, it floats to the surface in a vertical line without any push.
Try a pond snail floating on the surface of a pond, immerse it in water and disturb its soft body with a touch of tweezers or a stick. The leg will immediately pull back into the shell, and air bubbles will come out through the breathing hole. The mollusk will then fall to the bottom and be unable to rise to the surface on its own in any other way than climbing plants, due to the loss of the air float.
Reproduction
The pond snail is a hermaphrodite, although its fertilization is cross. The snail lays eggs that are enclosed in slimy, transparent cords attached to algae. The eggs hatch into small pond snails with very thin shells.
Content of pond snail
Some aquarists allow the keeping of pond snails in one common vessel, not realizing that this is often simply unacceptable. After all, if, say, the snail is grown mainly in artificial conditions (in an aquarium), the snail is placed there directly from a pond, a small lake or a stagnant reservoir. Wild-caught pond snails are more likely to be a source of infectious diseases and fish parasites. Very often, young aquarists are offered to buy mollusks in the bird market and in various pet stores.
If you still decide to start an ordinary pond snail, then you need to understand thata prerequisite for its content is the water temperature of about 22 ˚С and its moderate hardness.
