Hermit crabs form a class of more than 1100 different species. Though they are very social creatures, they derive their name from the fact that their bodies lack proper protection in the abdominal zone, making them very vulnerable and causing them to prefer hiding in well-protected places.
Hermit crabs are decapods, which means that they have 10 legs organized into five pairs. They have large antennae used for navigation and swimming and long, spiral-shaped abdomens that are soft, therefore protected by the animal with the help of empty seashells found on the bottom of the sea. As hermit crabs grow, they need to change the shells they used for protecting themselves. To avail themselves to such shells, these crabs form a vacancy chain, that is, they stand in a queue, the largest crabs first, so the bigger the hermit, the higher the chance to find adequate shelter.
Hermits live between 30 and 70 years. Young crabs go through several different stages during their development. The first two stages take place while still inside the shell, while the third phase is the actual hatching, when the crab larvae emerge. In this stage the crab has large antennae, spines and a long abdomen. The animal goes through several molting stages before reaching maturity. Molting occurs every 12-18 months and the new skeleton requires about 10 days to harden properly.
Hermit crabs have a varied diet. While some species subsist on algae, others feed on living or decayed vegetation and carrion, but they are not picky when it comes to food. They avail themselves to food with the help of their claws. They have two large and two smaller claws, the smaller claws being used for pinching the food pieces off and then putting the piece into their mouth.
During the mating process, the male places his packets of sperm into the female’s orifices called gonopores. The fertilized female moves away for the ocean and carries the eggs for about 30 days. However, for releasing the eggs, all hermit crab species need the ocean as the only environment where juvenile crabs can grow is the sea (the reason why hermit crabs are unable to breed in captivity). The growth period lasts for about two more months, during which the larvae go through several different stages of development before they become mature hermit crabs, able to survive outside the water.