Crustaceans are an order of arthropods that have a calcareous outer shell called the carapace. Typical crustaceans have compound eyes, two pairs of tentacles, and several segmented appendages. Arthropods in the sea, mainly crustaceans, there are more than 30,000 species in the world***, such as prawns, crabs and so on. They live in a variety of ways: some swim in the water, some undersea crawling, some attached to the rocky reefs on the fixed life, some burrowing, and some parasitic.

Crustaceans

It is easy to see how crustaceans such as crabs and crayfish got their names by observing them. Their bodies are encased in very hard, chalky armor, and they seem to hide in a crustacean shell. Crustaceans belong to the group of animals known as arthropods, a group that also includes insects and spiders. Like other arthropods, crustaceans are protected by their exoskeleton and move around on jointed legs. There are nearly 40,000 species of crustaceans, and while not many live on land, a large number live in freshwater and the sea, the smallest not much bigger than a sentence but the largest more than a meter in diameter.

Crustacean Anatomy

Crustaceans vary greatly in size and shape, but they share some **** of the same characteristics; all grow ectodermal skeletons and molt regularly as they grow larger. They also have two pairs of antennae and generally bear compound eyes. Crustaceans usually breathe through gills at the base of their legs, and some have special legs that allow them to swim. Crabs and crayfish are both have crawling legs, the front pair having become powerful chelae.

The life cycle of crustaceans

Like many insects, crustaceans begin life as eggs, and when they grow up, their shape changes completely. A female crab cautiously protects her eggs until they hatch, the eggs produce floating larvae called larvae, in the water they drift away with the current and slowly turn into large-eyed larval crabworms, eventually settling on the sea bed, these larvae then by slowly grow into the shape of an adult and move to shallower waters and shores.