A subclass of crustaceans. Has a constant number of segments in the head, thoracic and ventral parts, and abdominal legs. There are 5 pairs of limbs and a pair of facet eyes on the thorax. Respiratory and circulatory systems are well developed. The stomach consists of two chambers, chewing and filtering, and has a complex digestive gland. The genital foramen always opens on the last thoracic segment in males and on the sixth in females. There are 13 suborders, the most important being Mysidacea, Isopoda, Amphipoda, Stomatopoda, Decapoda and others. There are over 23,000 species. Mostly marine forms. Known in fresh water. Widespread. Many higher crustaceans are fished and farmed.
     The term "superior" is not entirely accurate. If the constancy of the number of thoracic and ventral segments can be taken as a sign of higher organisation than their inconsistency in other crustacean subclasses, the presence of ventral limbs, on the other hand, indicates less specialisation than their disappearance in other subclasses. In all likelihood, the higher crustaceans evolved independently of the other subclasses, each retaining some primitive features inherited from common ancestors.
     Higher crustaceans are generally larger than crustaceans in other subclasses. They are extremely widespread: they inhabit a wide variety of water bodies and have partially adapted to life on land. The systematics of the subclass is very complex: it is divided into superorders, which in turn are divided into orders. There are five such suborders.

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Higher crayfish (Malacostraca)

Tags: Higher crayfish (Malacostraca)