Who is this cancer?

Today we talk about the animal such as cancer. What do we know about them, except that it's a great snack to beer? More details about them we will talk Vashchenko A. N. - officer : raki-kiev.com.ua.

Crayfish, crustacea (crustaceans) - are a class of aquatic animals belonging to the phylum Arthropoda. There are about 20,000 species of crayfish. The length of their body: starting from fractions of mm to the 80 cm Body consists of: the chest, head and abdomen. It is covered with a chitinous cuticle, which often contains lime and forms a shell. Cancers on the head there: two pairs of lower jaws (called maxilla), upper jaws (called mandibles) and two pairs of antennae (called antenna and antennule). Antennae play the role of the sense organs, and sometimes organs of motion. All other appendages take part in the chopping and the retention of food. It is such that the 4-d anterior thoracic segment merge with head cancer that turns the limbs of crayfish in nogocheljusti. The remaining thoracic limbs cancer often bear gills and are used for movement.

Most of these animals is the bulk of plankton and lives in the seas. Live only on land, some cancers (sea fleas, woodlice, some of tropical decapod). The large majority of plankton crayfish eat bacteria and other unicellular organisms. Bottom crayfish eat plants, particles of organic matter or animals. Amphipods eat dead bodies of animals, thus helping to clear the waters. Crayfish can live only in clean enough water. Consequently, the population of this species in recent years has declined. Immediately after the river is polluted, cancers disappear. Conversely, if the river you will see crawfish - this means that the water in it pure and you can drink it safely (of course, before drinking, water should be boiled).

Method crayfish movement

Do cancers have 10-free legs. Some of the limbs (nogocheljusti) «merged" with his head. 2-ve from free feet - it's powerful claws cancers can even grasp your finger (by the way, it is very painful). The remaining 3-ri pairs of legs crayfish serve them for movement. Crayfish can move backwards, slowly creep forward and even move sideways. Often, like all the other animals, crayfish moving his head forward. But the truth is “run” on their thin legs cancers can't. Therefore, seeing the danger, cancers are: raking the water "tail" with the help of very sharp movements, as a result they "jump" back. They even can swim "backwards".

the Constellation Cancer

There are scientists who claim that Cancer constellation called thus using the fact that crabs walk backward. The thing is that 2000 years ago at the summer solstice the Sun was in this constellation. And when it began to decline over the horizon, "stand back" like a crab.

Translated by "Yandex.Translate": translate.yandex.ru.