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Description:
Hermit crabs have a hard shell called a carapace covering the head and cephalothorax, with the rest of the body being soft and uncovered. The hard exoskeleton of chitin is the hermit crab’s method of supporting its body. It places its soft abdomen into a variety of empty shells in its lifetime. A hermit crab looks somewhat like a lobster when out of its shell.
The thoracic area has five pairs of legs, with the first pair modified into claws. The right claw is much larger than the left. The head of the crab has two pairs of sensory antennae and a pair of compound eyes on movable stalks.
Males are usually larger than females.
Habits and Adaptations:
Crabs continue to grow and molt throughout their lives, but growth slows down with age. When a hermit crab reaches adulthood, it must continually find larger and larger shells. Before the crab moves from one shell to another, it uses its antenna to carefully examine and measure the shell and its opening. Next, it lifts and weighs the shell several times. Finally, the crab feels inside the shell and sticks its head through the opening. Often after switching to a new shell, the crab will return to the old one several times before finally settling into its new home. Finally, the abdomen is placed in the shell with the head and pincers of the crab extend from the opening of the shell to find food.
Crabs can move forward, backward or sideways.
Diet, Breeding and Miscellaneous:
Hermit crabs are omnivores.
Depending on the species, breeding occurs seasonally or year round. Copulation can occur with either the male or female on top. Eggs number in the thousands and are carried by the female for approximately one month. Then the fertilized eggs are released into the ocean, hatch and go through four to six larval stages. Following the last larval stage, the larvae metamorphoses into a young hermit crab.
One species of anemone is always found on a shell inhabited by a hermit crab. Sometimes several anemones may crowd onto one shell. An anemone living on a hermit crab will change shells with the crab when the crab moves to a new shell.
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