Bezubki: structure and way of life

Bezubka is one of the most common bivalve mollusks, represented in domestic water bodies. Lives this species mainly on sandy and silt bottom. Let's consider in detail the structure of the shell of the toothless, we will learn what way this life is led by this mollusc.

Structure

Considering the structure of the shell of the toothless, outer and inner layers, it is worth noting that such a mollusc is extremely similar to another mollusk, a perlite, common in our reservoirs. The shape of the shells of these species is almost identical. However, toothless are more massive, and also have a thin outer shell structure. In addition, these creatures do not contain teeth on the inner side of the shell, forming a kind of lock, like a perlova. Hence the name - the toothless one.

Considering what the shell of a toothless shell looks like, the external structure of the shell, it should be noted that the latter is formed from two keratinous halves that are closely adjacent to one another. In front of the sink has an extension. The posterior region narrows. In a live, freshly caught mollusk, the valves are always securely closed, which is a protective reflex against predators.

To consider the internal structure of the toothless shell, you will have to cut the internal muscles that keep the shell closed. In a natural environment, the shell is opened by contracting the horny, firm ligament that runs along the entire dorsal part of the body of the mollusk. While the toothless is alive, its protective shell remains closed most of the time. When the animal dies, the muscles relax, and the valves open arbitrarily.

What is a toothless shell?

It should be noted that the structure of the shell of the toothless and pond snake, as well as of the same perlovic, is almost identical. The outer shell of the mollusk, in fact, is a keratinized calcareous layer, covered with a petrified silty coating of a brownish hue. If a piece of shell is placed in a solution of hydrochloric acid, gas bubbles will start to be actively extracted from the material. This indicates the organic structure of the outer shell of the mollusk.

Studying the toothless structure, you can see that the shell contains a pearl layer, which looks like a thin plate overlapping each other. Shell surfaces here have an attractive iridescent gleam.

In general, the cornified part of the body of the mollusc consists of three layers. The outer part of the shell forms a keratinized calcareous layer. Inside, the carving of the toothless is lined with porcelain and pearlescent layer.

Soft fabrics

Investigating what are toothless, the structure of the mollusk, it is necessary to tell about the internal, mantle cavity of such an animal. Opening the shell doors, you can see folded skin structures, which are located on both sides of the body. The edges of such soft tissues smoothly pass into the shell and connect with the cornified structures with strong bonds.

The external structure of the toothless is represented by structures that are sufficiently resistant to mechanical influences. In turn, the inner part of the mollusc is extremely soft. For this reason, these animals are also called spineless. In the mantle, folded cavity are internal organs. To examine them, it is enough to turn away the soft tissues.

The shells in the back of the body of the mollusk dock tightly. There is a small gap through which fresh water enters the sink. The liquid is filtered out by the digestive organs of the toothless and is taken out through a special upper opening on the body. The movement of water in the mantle cavity is supported by rhythmic oscillations of so-called ciliated cilia that cover the internal organs of the mollusk.

Breathing and nervous system

In the mantle cavity of the molluscum there are gills. They can be distinguished from other soft tissues by a characteristic brown shade. On each inner side of the shell shell there is a pair of gills. The water that enters the sink brings not only nutrients but also oxygen to the tooth.

As for the nervous system, in the toothless it is primitive and consists of several pairs of nerve nodes. With the help of nerve fibers located in soft tissues, the mollusc perceives the stimuli and responds to them. So, when you touch the open shell, its sashes instinctively close.

Features of reproduction

Bezubki are different sexes. Outwardly females are no different from males. During the mating season, mollusks concentrate in a certain area of the reservoir. Male individuals throw the seed into the water. In the body of females spermatozoa fall through a special siphon, after which the fertilization of eggs begins. Of the latter, larvae develop. By means of the same siphon, not yet fully formed individuals are ejected outwards.

Slamming the rudiments of the leaves, the larvae float from the bottom and try to solidify on the scales of swimming fish. Further on the body of fish formed a kind of cocoon. Inside the mollusk continues to grow and grow in size. After a few weeks young young people, whose structure becomes more similar to adults, tear the skin of the "master" and fall to the bottom of the reservoir. Thus, in fact parasitizing on fish, the larvae of the mollusk occupy new habitats.

Lifestyle

The toothless, whose structure was described above, lead a sedentary lifestyle. Such mollusks feed passively. Bezubki filter out from the water primitive organisms and particles of plants. The latter fall into the mantle cavity through the oral blades - small leathery folds located in the anterior part of the body. Movement of ciliary cilia useful substances are forced into the digestive organs.

To trace the way of life of a toothless animal and the behavior in a natural environment, it is enough to place a mollusk in an aquarium that has a sandy bottom. After passing some time, you can notice the expansion of the shells of the shell. Through the formed slit outward, a leathery fold appears, through which the animal moves along the bottom. By itself, the toothless groove leaves a shallow groove on the surface of the sand. Within an hour the mollusc can overcome a distance of no more than 30-40 centimeters.

Finally

Apparently, toothless are typical representatives of primitive bivalve mollusks. Such animals are widely dispersed in ponds and rivers, since they do not have natural enemies. Unlike the same oysters and mussels, toothless ones are not used for human consumption.