If you've ever been to a pet store or on a beach vacation, you've interacted with hermit crabs.
These nocturnal crustaceans can be classified into two types: marine and land hermit crabs. While often thought to be solitary creatures because of their name, they actually prefer to live in groups.
Hermies have been known to sleep in piles and thrive in captivity when they live in groups of two or more and, with proper conditions, have been known to live anywhere from 5 to 15 years!
Hermit crabs have modified gills instead of lungs, which means that they need a high level of humidity in their crabitat. These gills must be kept moist in order for them to breathe. Hermit crabs also need a variety of shells to "change" into when they outgrow their current shell.
If there aren't enough open shells, they can fight for real estate, which can be fatal to the weaker of the crabs. In captivity they eat a commercially-made diet or you can make your own.
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Hermit crabs have two pairs of antennae. The outer, long pair is used for feeling their surroundings, while the inner, bent pair is used to taste and sense their environment.
Their faceted lenses are on movable stalks, and can sense very small movements.
They have three sets of movable mouth parts called maxillipeds.
Claws and Legs
Their big claw is one of the first pair of legs; they have five pairs total. This claw is used defensively, as well as to seal up the opening of their shell. Their small claw is the second of the first pair of legs and is used for feeding and drinking.
The second and third pair of legs are used for walking and climbing. There are also fourth and fifth pairs of legs that are located inside the hermit crab's shell. They are used for moving in and out of the shell as well as cleaning the gills and removing waste from their shell.
Body and Gills
A hermit crab body is called the cephalothorax. The gills are located between the fourth and fifth pair of legs, and are used for breathing.
Hermit crabs have a soft abdomen, which contains all their digestive and reproductive organs.
Protects the fragile abdomen and used for housing and protection.