Cryptochiridae

Cryptochiridae is a family of crabs known commonly as gall crabs or coral gall crabs. They live inside dwellings in corals and cause the formation of galls in the coral structure.[1][2] The family is currently placed in its own superfamily, Cryptochiroidea.

Gall crabs are sexually dimorphic, with males being much smaller than females. Contrary to females, most males are free-living and "visit" females for mating.[1][3]

These crabs are most common in shallow waters where they live in association with stony corals, but they have also been recorded from mesophotic zones and deep waters.[4][5] They likely feed on mucus secreted by their coral hosts, as well as various detritus. Some species are thought to be filter feeders.[1]

Because crab size is related to gall size, it is likely that the crabs form the galls, rather than living randomly in a dwelling within a coral. Related groups of gall crab taxa share a similar gall type, suggesting that the crabs influence the morphology of the galls.[6]

The family contains the following twenty-one genera:[7][8]