Crustaceans

Crabs, a family of large marine crustaceans, are distinguished from other crustaceans by the presence of a large head shield; their body consists of a cephalothorax and abdomen with a two-branched caudal fin. Sizes vary. About 160 genera, about 9 thousand species. Distributed in tropical, subtropical and temperate latitudes of all oceans, lakes and rivers, as well as fresh waters. The caviar is large, up to 5–6 mm in diameter, unevenly colored or brownish-yellow. The protoplasm of a large number of eggs disintegrates some time after attachment to the water, and the liquid formed around the yolk surrounds the larvae with a shell. In this aquatic state, the larvae move using cilia. When the time comes for the larvae to hatch, the contents of the water that they absorbed along with the liquid and yolk from the egg begin to decompose and rot. Its temperature becomes very high, and the “baby” liquid dissolved in it, already enriched with nutrients in the form of decomposition products, continues to rot and even becomes useful for the larva, since it absorbs additional reserves of nutrients. As the larva develops, it independently moves to the surface of the water and, when the temperature reaches a certain value, it begins to hatch out. The temperature drops, and the lungs of the newborn crustacean are attached to the membrane for a more even distribution of gases in the body cavity. Coelomia in cancer