Hermit Crabs
INDEX
WHAT ARE HERMIT CRABS?
HERMIT CRAB FEATURES
HERMIT CRAB REPRODUCTION
HERMIT CRABS OF THE BAHAMAS
WHAT ARE HERMIT CRABS?
Hermit crabs are invertebrates (lacking a backbone) and have jointed legs and a hard exoskeleton, as do insects, lobsters and spiders, forming a group known as the Arthropods. The hermit crabs have two pairs of antennae and 10 legs, which classifies them with the crab, lobster and shrimp group known as the Decapods (10 legs). The hermit crab is very crab-like, the first 2 legs are large claws and the other legs are quite small. However, the hermit crab is not covered with a hard exo-skeleton like a true crab. The abdomen (hind segment of the body) of a hermit crab is soft and vulnerable. Therefore, they have to protect their soft body parts by “acquiring” the shell of another animal.
There are about 500 known species of hermit crabs in the world. Most hermit crabs are aquatic and live on the sea floor, but some are terrestrial (land-based). They are found in tropical regions of South America, North America, the Caribbean and Australia. All hermit crabs are omnivores (eating plants and animals). The land hermit crabs particularly feed on vegetable matter, dead animals and even fecal matter. These crabs play a very important role in the removal of decaying material in their habitats.
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HERMIT CRAB FEATURES
Hermit crabs have two pairs of antennae that they use for sensing their environment. They have one large claw which is used for defense and a smaller claw which is used for climbing and carrying food to the mouth. When the hermit crab is in its shell only 4 of its legs are exposed and used for moving about, the other four legs are kept inside the shell and are used to move about in the shell and to clean the shell of waste products.
Hermit crabs live in the shells of gastropods (snail-like animals). Therefore, their abdomen is coiled in shape. To be able to hang onto the shell, they have hooks at the very tip of their abdomen. If the hermit crab feels threatened it will recoil into its shell and it is nearly impossible to pull it out. When the hermit crab out-grows its shell it will search for a new, larger shell and crawl into it.
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HERMIT CRAB REPRODUCTION
All hermit crabs do a mass migration to the shore lines for breeding purposes, being nocturnal, this migration occurs at night. The fertilized eggs are released into the water, where they immediately burst and release the larvae (or zoeae). The larvae will float aimlessly in the ocean for about 50 days where it will settle on the ground (post larval stage) for a month before venturing out of the water and beginning its journey on land. Once land bound it will continue to metamorphose (change) to suit its new life on land and during this time their gills become more lung-like in function.
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HERMIT CRABS OF THE BAHAMAS
The Bahamas has an aquatic hermit crab and a terrestrial hermit crab called the Caribbean land hermit crab.
Caribbean land hermit crab (Coenobita clypeatus)
Also known as the Soldier crab, this species is found near the shores of all of the tropical, eastern Americas. It can grow to the size of about a man’s fist. In the Bahamas their migration is usually during the second full moon in August. As the crabs scurry across the leaves on the forest floor they can make quite a racket. This noise is very well known through out the family islands in the Bahamas as well as all Caribbean. In the Bahamas there are also stories of this migration noise scaring away invaders.
Ardastra house several Caribbean land hermit crabs. Some of them are of a considerable size.
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