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Hermit crabs are crustaceans of the group Paguroidea, closely related to true crabs of the group Brachyura. Most hermit crabs salvage empty seashells to shelter and protect their soft abdomens. There are about five hundred known species of hermit crabs in the world; although they are mostly aquatic, there are also some terrestrial species. A number of species, most notably king crabs, have abandoned seashells for a free-living life; these species have forms similar to true crabs and are known as carcinized hermit crabs. Other species inhabit shells as juveniles and abandon them as adults, most notably the coconut crab.
The species most commonly kept as pets in the United States are the Caribbean Hermit Crab (Coenobita clypeatus) and the Pacific Hermit Crab (Coenobita compressus). In Europe, the Common Hermit Crab (Eupagurus bernhardus) is popular.
Geographical variance
The Flat-clawed Hermit Crab (Pagurus pollicaris) is widely distributed along the Atlantic seacoast of the United States.
The two terrestrial species of hermit crabs found in Australia are the Australian Land Hermit Crab (Coenobita variabilis) and the Strawberry Land Hermit Crab (Coenobita perlatus). The variabilis species is found in the northern parts of Australia, including northern Western Australia, the Northern Territory and northern Queensland. Ranging in size between a pea and a tennis ball, they closely resemble the Pacific Hermit Crab in appearance and both species have a shortened aquatic development [1].
Coconut crab
Birgus latro, also known as the 'Robber Crab' or 'Coconut Crab' is the largest terrestrial arthropod. While the juvenile Birgus will use a seashell to protect their abdomen, adult crabs abandon the seashells once the shells harden over the abdomen. This evolution to remove reliance on seashells for hydration and protection has enabled this hermit crab to grow to larger sizes, for it is no longer restricted by availability of larger seashells. Their strong legs enable them to climb coconut trees, and their muscular claws enable them to pierce and break apart coconut shells (hence the common name Coconut Crab).
See the full article for more information.
Commonly kept marine hermit crabs
There are several species of hermit crabs that are common in the marine aquarium trade. These omnivorous or herbivorous species are useful in the household aquarium as scavengers, eating algae and other debris.
The scarlet hermit crab, or Red Reef hermit crab (Paguristes cadenati), is a handsome and interesting species with a bright red body and yellow eyestalks, and stays rather small (about an inch or two across). Smaller species of a similar passive nature include the zebra hermit crab (brown legs with white bands), the red-tip crab and blue-legged crab (very nifty beast).
While most species available in pet stores are small like those listed above, and are simply scavengers, others may grow quite large (some on the Pacific coast can grow to a foot!) and may eat corals, clams and other crustaceans. So be sure to ask if the species is not clearly marked.
Most hermit crabs will appreciate a salinity of between 1.023 and 1.025, temperatures between 75 and 80 degrees Fahrenheit, with a good bed and algae to graze on and a variety of shells to change into. They will happily switch shells frequently if given the opportunity - an interesting display to watch.
References
- [1] Harvey A & Brodie R, "Development of the terrestrial hermit crab, Coenobita compressus, in the laboratory". 2001. Journal of Crustacean Biology, vol 21. 715-732.
- ITIS Standard Report Page: Paguroidea (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=206947)
External link
- Crab Street Journal (http://www.crabstreetjournal.com/), online magazine for land hermit crab owners
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