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Hermit crabs fighting over a shell A hermit crab retracted into a shell of Acanthina punctulata and using its claws to block the entrance. As hermit crabs grow, they require larger shells. Since suitable intact gastropod shells are sometimes a limited resource, competition often occurs between hermit crabs for shells. The availability of empty ...
Anomura (sometimes Anomala) is a group of decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word crab, all true crabs are in the sister group to the Anomura, the Brachyura (the two groups together form the clade Meiura).
The example of king crabs (family Lithodidae) evolving from hermit crabs has been particularly well studied, and evidence in their biology supports this theory. For example, most hermit crabs are asymmetrical, and fit well into spiral snail shells; the abdomens of king crabs, even though they do not use snail shells for shelter, are also ...
Crabs vary in size from the pea crab, a few millimeters wide, to the Japanese spider crab, with a leg span up to 4 m (13 ft). [6] Several other groups of crustaceans with similar appearances – such as king crabs and porcelain crabs – are not true crabs, but have evolved features similar to true crabs through a process known as carcinisation .
The phylogeny of king crabs as hermit crabs who underwent secondary calcification and left their shell has been suspected since the late 1800s. [4] They are believed to have originated during the Early Miocene in shallow North Pacific waters, where most king crab genera – including all Hapalogastrinae – are distributed and where they exhibit a high amount of morphological diversity.
Coenobita pseudorugosus occupy the supralittoral region, in conjunction with other terrestrial hermit crabs such as C. cavipes and C. rugosus. [3] As with all terrestrial hermit crabs, they are subject to limited availability of empty gastropod shells that are suitable as a shelter, and thus an individual must compete with conspecifics as well as other species of terrestrial hermit crabs.
Intrigued — and somewhat concerned — researchers scoured the internet for images of hermit crabs using human trash instead of natural shells, the study said. They found almost 400 examples.
The midden constitutes a source of empty shells available for use by hermit crabs, and P. puncticeps individuals have been observed carrying empty shells away from the pile. [4] The middens also attract hermit crabs which feed on food scraps left by the octopus, but feeding close to the octopus den is a risky business.