Paguridae (hermit crabs; class Malacostraca, order Decapoda)
A family of crustaceans which use empty gastropod shells as cover for their soft abdomens. The abdomen spirals to the right, and the shell is held by tubercles on the uropods
, by abdominal contraction, and by the larger, left uropod which hooks round the columella
of the shell. As the crab grows, it selects new shells with great care, the colour contrast, weight, and fit being gauged before the crab takes up occupancy. In several species the shells become overgrown by sponges or bryozoan colonies. The chelae
are subequal, or sometimes with the right one larger and modified as an operculum
to close the shell. Pleopods
are reduced except on the left side, where they function for respiratory current production and for egg attachment. Hermit crabs are very active inhabitants of coastal and deep waters.