Question

write a short essay of cheif characters of crustaceans in 6 points

Answer 1

The largest crustaceans belong to the Decapoda, a large order (about 10,000 species) that includes the American lobster, which can reach a weight of 20 kilograms (44 pounds), and the giant Japanese spider crab, which has legs that can span up to 3.7 metres (12 feet). At the other end of the scale, some of the water fleas (class Branchiopoda), such as Alonella, reach lengths of less than 0.25 millimetre (0.009 inch), and many members of the subclass Copepoda are less than one millimetre in length. The range of structure is reflected in the complex classification of the group. Some of the parasitic forms are so modified and specialized as adults that they can only be recognized as crustaceans by features of their life histories.

Answer 2

Answer:

Some Characteristics of Crustaceans:

• A hard exoskeleton made of calcium - no internal skeleton.
• The head has two compound eyes, two pairs of antennae, and three pairs of mouthparts.
• A pair of green glands excrete wastes near the base of antennae.
• The abdominal segments have swimmerets (swimming legs)
• The sexes are separate. Eggs are attached to the swimmerets (swimming legs) of the female. The first pair is enlarged in the male (it is used to pass sperm to the female).
• The tail is fan-shaped, and ends in uropods and a telson.
• The circulatory system is open; there is no heart and the "blood" is pumped by vessels into sinuses, and does not flow in a closed loop).
• The nervous system consists of a primitive ventral nerve cord and ganglia system (similar to those of an earthworm).

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