One of the first creatures that appeared on Earth were snails. Counting a huge number of varieties in shape, size, distinctive features, they live in almost every corner of the planet, playing an important role in its ecosystem.
Surely every person at least sometimes wondered: what is the structure of snails? Do they have eyes, ears, teeth, brain?
The structure of the snail can be seen on the example of a giant representative of the gastropod class - Achatina, an inhabitant of tropical African forests, which has gained popularity as a pet. Simplicity of maintenance, omnivorousness, lack of smell, unpretentiousness and affection (each individual knows his master well) are the factors due to which such a unique creature becomes a favorite in many houses. In captivity, Achatina are able to live for about 10 years.
The structure of the snail Achatina
The structure of Achatina, the largest representative of land mollusks, is quite simple: the head, trunk and shell, the size of which can reach 25 centimeters.
On the head is the mouth opening and tentacles - long and mobile, with eyes at the end. The ability to see surrounding objects in Achatina is measured only by a distance of 3 centimeters. In this case, the snails are very sensitive to lighting, especially to bright, the intensity of which is perceived not only by the organs of vision, but also by photosensitive cells located on the body.
The snail's mouth is equipped with teeth (about 25 thousand pieces), but not in the usual sense. This is a device called "radula", which is a small "grater" and adapted for grinding food.
Unfortunately, the snail has no ears, so it does not hear anything. The lack of hearing is compensated by the smelling organs of the mollusk: it is the skin of the front of the body and small swellings located at the tips of the tentacles. The snail is able to feel the smell of chemicals (alcohol, gasoline, acetone) at a distance of 4 cm, it will feel the aromas of food in about 2 meters. The structure of snails, thanks to the same tentacles and the sole - the organs of touch, gives them the ability to perceive the texture and shape of surrounding objects, getting acquainted in this way with the outside world.
Pet - Achatina
The structure of the snail Achatina, as well as the ability, with apparent simplicity, have interesting features. So, they have a long-term memory: Achatina can remember the location of food sources and return to them. Adults have a permanent resting place; when moving the snail to another place (within 30 meters), it crawls to its native, more familiar. Young specimens are characterized by mobility and can travel long distances throughout the day; also have the ability to migrate long distances.
Salient features and snails
The structure of the snails is due to their terrestrial existence, in connection with which the mollusks have a well-developed sole, equipped with two foot glands that secrete mucus, and transmit waves of contractions through itself. These specific features result in optimally easy movement of the snails on a dry surface.
Wrinkled skin along with the lung, which in a snail in one instance, takes an important part in the respiratory process. The internal structure of the cochlea is characterized by the presence of a heart, kidney, nerve endings. According to experts, snails are not able to experience pain. This strangeness is due to the absence of the brain and spinal cord, instead of which there is an accumulation of ganglia - nerve nodes that together form the nervous system of a scattered-nodal type.
Shell protective functions
The snail shell, strong enough and massive, performs the following functions:
- protects the soft body from mechanical damage during movement;
- protects from potential enemies;
- protects the body of the snail from drying out.
The structure of the snail, or rather its shell, is directly affected by the climatic conditions in which it lives. So, with high humidity, the shell is thin and transparent; in dry and hot climates, its walls become thicker, and the color becomes white (reflects the sun's rays and protects the snail from overheating).
Meet the grape snail!
The structure of the grape snail is no different from the structure of the remaining species: the same shell, trunk and head with tentacles. Unless the size, unlike Achatina, is an order of magnitude smaller. And the way of life is close to field conditions, not as an example to domestic Achatina.
These are endless fields, gardens, forests, where the most comfortable places for snails are raw moss, the shade of plants or stones, under which you can hide from the heat.
The monochromatic shell of the grape snail is spherical, has a rounded shape and reliably protects the body of the mollusk from negative external factors. The leg with which the snail moves is large and muscular.
When moving, glands secrete mucus that softens friction with the surface. The average speed of movement of a grape snail is 1.5 mm / sec.
How do snails breed?
The special structure of snails directly affects the reproduction process, in which each individual acts as a male and a female. To do this, two snails are playing a love game, which consists in carefully feeling each other, and then tightly merging the soles.
In this way, mollusks exchange sex cells. Eggs coated with a nutrient membrane and having a supply of substances necessary for the development of snails are laid in heaps of 20-30 pieces in pits, which are then buried. After 2-3 weeks, the young generation appears, which in 1.5 months turns into full-fledged adult snails.