Toothless is one of the most common bivalve mollusks represented in domestic reservoirs. This species lives mainly on a sandy and silty bottom. Let's look at the structure of the toothless shell in detail, find out what kind of life this mollusk leads.
Structure
Considering the structure of the Toothless shell, the outer and inner layers, it is worth noting that such a mollusk is very similar to another mollusk common in our reservoirs - pearl barley. The shape of the shells of these species is almost identical. However, the toothless are more massive, and also have a fine structure of the outer shell. In addition, these creatures do not contain teeth on the inner side of the shell, forming a kind of castle, like a barley. Hence the name went - toothless.
Considering how the toothless shell looks, the external structure of the shell, it should be noted that the latter is formed from two keratinized halves that are tightly adjacent to each other. The front of the sink has an extension. The posterior area narrows. In a living, freshly caught mollusk, the flaps 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 the natural environment, the shell opens by shortening the corneous strong ligament that runs along the entire dorsal part of the mollusk body. While the Toothless is alive, its protective carapace remains closed most of the time. When the animal dies, the muscles relax and the flaps open arbitrarily.
What is a toothless conch?
It should be noted that the structure of the toothless shell and the pond, as well as the same barley, are almost identical. The outer shell of the mollusk, in fact, is a keratinized calcareous layer covered with a petrified silty bloom of a brownish tint. If a piece of the shell is placed in a solution of hydrochloric acid, gas bubbles will actively stand out from the material. This indicates the organic structure of the outer shell of the mollusk.
Studying the toothless structure, one can notice that inside the shell there is a pearlescent layer, which has the form of thin plates lying on top of each other. The sink surfaces here have an attractive rainbow sheen.
In general, the keratinized part of the mollusk body consists of three layers. The outer part of the shell is formed by a keratinized calcareous layer. Toothless carapace is lined with a porcelain and pearl layer.
Soft fabrics
Exploring what the toothless, the structure of the mollusk is, one should talk about the internal, mantle cavity of such an animal. Opening the shell flaps, you can see the folded skin structure, which are located on both sides of the body. The edges of such soft tissues smoothly pass into the shell and are connected with keratinized structures by strong ligaments.
Toothless external structure is represented by structures that are sufficiently resistant to mechanical stress. In turn, the inner part of the mollusk is extremely soft. For this reason, these animals are also called soft-bodied. In the mantle, folded cavity are the internal organs. To examine them, it is enough to unscrew the soft tissue.
The cusp flaps in the back of the mollusk body are not tightly coupled. There is a small gap through which fresh water enters the sink. The liquid is filtered by the digestive organs of the toothless and is discharged through a special upper opening on the body. The movement of water in the mantle cavity is supported by the rhythmic vibrations of the so-called ciliated cilia that cover the internal organs of the mollusk.
Breathing and nervous system
In the mantle cavity of the mollusk there are gills. You can distinguish them from other soft tissues by their characteristic brown hue. A pair of gills is contained on each inner side of the shell leaf. The water that enters the sink brings the toothless not only nutrients, but also oxygen.
As for the nervous system, in toothless it is primitive and consists of several pairs of nerve nodes. With the help of nerve fibers located in the soft tissues, the mollusk perceives stimuli and responds to them. So, when you touch the open shell, its wings instinctively close.
Propagation Features
Toothless are heterosexual creatures. Outwardly, females are no different from males. During the mating season, mollusks concentrate in a specific area of the reservoir. Males throw the seed into the water. Sperm enter the body of females through a special siphon, after which the fertilization of eggs begins. Of the latter, larvae develop. Through the same siphon, not yet fully formed individuals are thrown out.
Clapping the rudiments of the valves, the larvae emerge from the bottom and try to gain a foothold on the scales of swimming fish. Further, a peculiar cocoon is formed on the body of the fish. Inside, the mollusk continues to develop and increase in size. After several weeks, young toothless teeth, the structure of which becomes more similar to adults, tear the skin of the "owner" and fall to the bottom of the reservoir. Thus, in fact, parasitizing on fish, the larvae of the mollusk occupy new habitats.
Lifestyle
Toothless, the structure of which was described above, lead a sedentary lifestyle. Such mollusks feed passively. Toothless ones filter out primitive organisms and plant particles from the water. The latter enter the mantle cavity through the oral lobes - small leathery folds located in the front of the body. By the movement of ciliated cilia, beneficial substances are driven into the digestive system.
To trace the toothless lifestyle and behavior in the natural environment, just put the clam in an aquarium that has a sandy bottom. After passing some time, one can notice the extension of the shell flaps. A leathery fold peeps out through the formed gap, thanks to which the animal moves along the bottom. On its own, the toothless leaves shallow grooves on the surface of the sand. Within an hour, the mollusk is able to cover a distance of no more than 30-40 centimeters.
Finally
As you can see, toothless are typical representatives of primitive bivalve mollusks. Such animals are massively settled in ponds and rivers, because they do not have natural enemies. Unlike the same oysters and mussels, toothless are not eaten by humans.