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The scheme of the body structure of crayfish

Crustaceans appeared about 545 million years ago, long before mammals. Despite their ancient origins, they still have wide species diversity and occupy an important niche in the food chain. There are a great many representatives of this class, they all have common features.

For the consideration of crustaceans, you can study the structure of river cancer, a representative of the class, which is quite common in Russia.

The representatives of the class of crustaceans are great, they all have common features

Crayfish has, like any other species, its Latin name – Astacus astacus L. It is distributed in the southeastern, central and northern regions of the Russian Federation, as well as in Ukraine, the Baltic States, Belarus and some other countries.

The structure of the body of crayfish has heteronomic segmentation and consists of two sections: accrete cephalothorax and segmented abdomen. The first is represented by a hard shell, which is formed by the head and thoracic trunk regions.

At the junction clearly visible furrow (seam).

The abdomen has a segmental structure and is covered with rigid plates. Gender of arthropods can be determined by the ratio of these two departments.

In females, the belly is larger than the cephalothora, and in males, respectively, the opposite.

8 pairs of differentiated limbs that correspond to the number of segments of an accrete shell depart from the cephalothora. The head section has a sharp spike in front, from which a pair of eyes located on moving thin stems sits on each side of the grooves.

The eyes have a facet structure, so that the arthropod is able to cover a large field of view.

On the front of the head, two pairs of movable antennae perform tactile and olfactory functions. One pair is shorter (antennula, or olfactory organs), the other is long (antennas, they are organs of touch).

Eyes cancer has a facet structure, so that the arthropod is able to cover a large field of view.

The first 3 pairs of limbs are represented by the oral organs or maxillary jaws. The first pair has the name of the upper jaws (mandibles), the other two, that is, the second and third pairs, are the lower (maxilla).

The fifth pair has the appearance of massive claws, the other four are thin walking legs.

The seven-segment abdomen is mobile and involved in swimming (6 and 7 segments form the tail fin) and in reproduction.

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The structure, function and location of the internal organs have a common appearance in crustaceans. Organs are organized into coherently functioning systems.

  1. Digestive system cancer has the form of a tube, each division of which performs its own functions. The following departments are successively running: the oral apparatus – the pharynx – the short esophagus – the stomach, consisting of 2 sections – the chewing gum (soaked in lime plates rub the food) and the filter (through two pile plates the food is filtered) – the intestine (absorption of microelements) – the anus located on tail blades.
  2. Circulatory system it is represented by a network of vessels along which the hemolymph moves (a colorless liquid that performs the functions of the blood). In the dorsal part of the thoracic region under the dashboard is the heart of crayfish. Since arthropods have an unclosed circulatory system, the vessels extending from the heart open into the body cavity. Gas exchange occurs between the hemolymph and the organs it flushes. Another important function is the release of nutrients into the internal environment. The blood takes the decay products and CO2, then it flows through the vessels into the gills, and then moves to the heart.

Since arthropods have an unclosed circulatory system, the vessels extending from the heart open into the body cavity.

  • Respiratory system The arthropod is represented by paired gills, which have the appearance of feathery thin outgrowths located on the walking legs of the cancer and on the maxillary jaws. The gills themselves are located in the cavity of the cephalothorax.
  • Nervous system Cancer is represented by a supraaryngeal paired knot, a pharyngeal nerve ring, and paired abdominal nerve trunks.
  • Secretive function perform green cancer glands. They are located in front of the head section and consist of two parts: the gland itself and the bladder. In the latter there is an accumulation of waste products, which were formed after digestion. They exit through the excretory pore near the antennas.
  • Gonads located in the cephalothorax, not paired. In females, the reproductive system is represented by an ovary with a pair of oviducts extending from it. In males, a pair of seed tubes depart from the testis. With the help of copulatory organs, seminal fluid is injected into the female’s genital tract (internal fertilization).
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