Hermit crabs are classified as a type of crustacean belonging to the super family Paguroidea. In spite of its classification under this lineage, they are not closely related to those referred to as true crabs. These so called hermit crabs typically inhabit places such as the intertidal zone.
Species of hermit crabs usually have soft and long abdomens. These body parts of the hermit crabs are well protected from predators through a salvaged hollow seashell mounted on the hermit crab's back. The body of the crab can retract into this hollow shell when threatened by predators. Most of the time, these crabs utilize the shell of the sea snails found in the shores. Whenever the hermit crabs develop in size, they tend to look for a bigger shell and dispose of the old one. This way of living in a "second hand" shell has brought about to the well-known name as "hermit crab", by similarity to a hermit or a solitary being who likes to live alone.
There are over five hundred of known species of hermit crabs, and out of this number, most of them live in water and in different depths of salt waters, encompassing the shorelines, shallow reefs and to the deep sea bottoms. However, there are also terrestrial hermit crabs that can be seen in some tropical areas.
There is a vast number of different species of hermit crabs that are typical in the industry of marine aquarium. To date, there has been 15 terrestrial hermit crabs species known in the whole world. The Australian land hermit crab (Coenobita varibilis), Carribean hermit crab (Coenobita compressus) and the Ecuadorian hermit crab (Coenobita compressus) are the most types of hermit crabs that are usually kept as pets. There are also some species kept as pets namely Coenobita rugosis, Coenobita cavipes, Coenobita brevimanus and Coenobita perlatus, however they are less common since they are not usually available and are not as popular.
Species of hermit crabs are classified either as omnivores, or those organisms that eat both plants and animals as their primary source of food, and herbivores, or those organisms that are adapted to eat plants. Due to their eating patterns, hermit crabs are very useful in the household aquariums acting as scavengers since they feed on debris and algae.
Hermit crabs were previously regarded as throwaway pets since they can only live for a few months. However, there are some species such as the Coenobita clypeatus that can survive for 23 years when appropriately taken cared of. Some species can also manage to live for over 32 years. The key to successfully raising hermit crabs as pets is to control the temperature and humidity in the environment and provide enough substrate to allow them to bury themselves.
