What kind of animal is a snail?

Snails are terrestrial species of Gastropoda in mollusca.

Gastropoda animals are named "Gastropoda" because their feet are located in the abdomen; Because it has a spiral shell, it is also called "single shell", which is the most diverse kind of mollusk.

These animals usually have asymmetric calcareous shells with various shapes, such as hat, cone, spindle or ellipse; Then some species of gills have no shells, forming inner shells, and a few species of shells disappear.

Adults are asymmetrical due to torsion. Even in the larval stage, shells are spirally curled, but some adults are symmetrical because of reverse torsion. Visceral masses are twisted and generally spiral.

The number of gill gland, submandibular gland and osphradium decreased to 65438 0. There is also 1 auricle, or 1 auricle of 2 auricles. There are 1 genital holes, which are located on the same side of anus and close to the neck opening. The head obviously has tentacles and eyes. A toothed tongue in the mouth. Usually, spiral division produces a trochoid, which develops into an adult through the larvae of the panel.

Extended data

Mollusks are a large class of invertebrates, second only to arthropods. Because most of these animals have a calcareous shell, they are also called "shellfish".

According to incomplete statistics, there are about 654.38+million species of mollusks in the world, and about half of them live in the ocean except terrestrial and freshwater shellfish. There are many kinds and shapes of mollusks. According to their different body structures, living species are usually divided into seven categories.

That is, branchiata, branchiata, branchiata, Gastropoda, Amphipoda, Bivalves and Cephalopoda.

1. Animals are worms with no shells. Found in coastal areas of China, there are few species.

2. Multi-plate turtles are commonly known as stone turtles. Their bodies are usually flat and oval, and their backs are covered with eight shells.

3. The shell of biped is tubular, slightly arched and shaped like horn or ivory, so it is called "ivory shell".

4. Bivalves, also known as "petabranchials", are named after the petaloid gills of such animals. Feet are usually flat and axe-shaped, so they are also called "axe feet". This animal's body is usually symmetrical left and right, and it has two shells to wrap the visceral mass. The shape and size of shells vary from species to species.

The species number of bivalves is second only to gastropods, which is a kind of high economic value. Common economic species are clam, oyster, scallop, clam and so on. In China, there are mature breeding techniques and high yield.

5. Cephalopods have symmetrical bodies, and their heads, feet and trunk are separated. Feet are very developed, born in front of the head, hence the name "Cephalopods". Most cephalopods have inner shells, some have degenerated inner shells, and only a few species have outer shells, such as nautilus.

Cephalopods are a very important class of mollusks. Although there are only 600 existing species, its annual output is 6.5438+0.6 million tons, which is an important marine bio-economic animal resource. Squid (soft fish, cuttlefish), cuttlefish (squid), octopus, etc. The daily consumption of coastal residents belongs to cephalopods.

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