Critter Corner

By: Bill Knauer

Hermit Crab is the common name for a number of marine crabs and for several related terrestrial crabs. They are found along the coasts of Europe and the Americas. Hermit crabs, also called robber crabs, are armorless animals, the largest of which are found along the Pacific coast and attain a length of up to 46 cm (18 in). They insert their abdomens into gastropod mollusk shells that they carry about with them for protection. The abdomens of the crabs are soft and asymmetrical, flexed and twisted to fit into the whorls of the borrowed shells. Their abdominal appendages are especially modified for keeping the shell firmly supported on the body. Hermit crabs often seek new shells because they have outgrown their old ones; they change their housing whenever chancing upon another shell into which they can fit.

Hermit crabs are divided into families partly on which of the two claws is bigger. Most hermit crabs are marine. The few terrestrial forms are. These are the one often seen in pet stores. Each species of hermit crab usually prefers one or two particular species of shell to occupy. There are over 20 different hermit crabs found in Alaskan waters. Some of these are less than ½ inches long. (Hey, somebody’s got to use the little shells; we can’t all have big homes!) Some hermit crabs even do a little redecorating by placing additional plant or animal material on their host shells. 

 Most hermit crabs are scavengers on dead plant or animal matter. The next time you are diving take a close look at those snail, welk , or triton shells on the bottom. Many will contain a hermit crab. Keep your eyes open for interesting creatures when diving in Alaska and elsewhere.