Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen), usually hidden entirely under the thorax. They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers. Many other animals with similar names – such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs, stone crabs, and crab lice – are not true crabs, but many have evolved features similar to true crabs through a process known as carcinisation.
Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an asymmetric abdomen concealed by a snug-fitting shell. Hermit crabs' non-calcified abdominal exoskeleton makes their exogenous shelter system obligatory. Hermit crabs must occupy shelter produced by other organisms, or risk being defenseless.
Ghost crabs are semiterrestrial crabs of the subfamily Ocypodinae. They are common shore crabs in tropical and subtropical regions throughout the world, inhabiting deep burrows in the intertidal zone. They are generalist scavengers and predators of small animals. The name "ghost crab" derives from their nocturnality and their generally pale coloration. They are also sometimes called sand crabs, though the name refers to various other crabs that do not belong to the subfamily.
The Caribbean hermit crab, also known as the soldier crab, West Atlantic crab, tree crab, or purple pincher, is a species of land hermit crab native to the west Atlantic, Bahamas, Belize, southern Florida, Venezuela, the Virgin Islands, and the West Indies. Adults burrow and hide under the roots of large trees, and can be found a considerable distance inland. As with other terrestrial crabs, they use modified gills to breathe air. Their shells help maintain the humidity necessary for gas exchange to function.
The Ecuadorian hermit crab also known as the Pacific hermit crab is a species of land hermit crab. It is one of the two land hermit crabs commonly sold in North America as pets, the other being the Caribbean hermit crab.
The Australian land hermit crab is a terrestrial hermit crab species, native to Australia. It is a nocturnal, omnivorous crustacean. They are gregarious and thrive in tropical areas near water.
Calappa hepatica, the reef box crab, is a common benthic species of box crab of tropical and subtropical parts of the Indian and Pacific Oceans and the Red Sea.
Ocypode is a genus of ghost crabs found in the sandy shores of tropical and subtropical regions throughout the world. They have a box-like body, thick and elongated eyestalks, and one claw is larger than the other in both males and females. They inhabit deep burrows in the intertidal zone. They are primarily nocturnal, and are generalist scavengers and predators of small animals. The genus contains 21 species.
Pagurapseudidae is a family of crustaceans in the order Tanaidacea. Like hermit crabs, they inhabit empty gastropod shells, but can be told apart from hermit crabs by the lack of a carapace, revealing the segmentation of the thorax, and by the greater number of legs: hermit crabs have five pairs of legs, of which the first has large claws, and the last is highly reduced, while in Pagurapseudidae, there is one pair of claws, plus six further walking legs.
Coenobita perlatus is a species of terrestrial hermit crab. It is known as the strawberry hermit crab because of its reddish-orange colours. It is a widespread scavenger across the Indo-Pacific, and is also traded to hobby aquarists.
Coenobita brevimanus is a species of terrestrial hermit crab belonging to the family Coenobitidae, which is composed of coastal living terrestrial hermit crabs. From there it belongs to the genus Coenobita, one of two genera split from the family, which contains sixteen species. The Latin origins of the species name, brevimanus, come from the adjective brevis ("small") and the noun manus ("hands"). It is known as the Indos crab or Indonesian crab because it is primarily distributed throughout the Indo-Pacific.
Pagurus novizealandiae, or the New Zealand hermit crab is a hermit crab of the family Paguridae, endemic to New Zealand. Its body is up to 16 millimetres (0.63 in) wide.
The coconut crab is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest terrestrial arthropod in the world, with a weight up to 4.1 kg (9.0 lb). It can grow to up to 1 m in length from each tip to tip of the leg. It is found on islands across the Indian Ocean, and parts of the Pacific Ocean as far east as the Gambier Islands and Pitcairn Islands, similar to the distribution of the coconut palm; it has been extirpated from most areas with a significant human population, including mainland Australia and Madagascar. Coconut crabs also live off the coast of Africa near Zanzibar.
Pilumnus hirtellus, the bristly crab or hairy crab, is a species of European crab. It is less than 1 inch (25 mm) long and covered in hair. It lives in shallow water and feeds on carrion.
Pagurus sinuatus is a large species of hermit crab found in Australia and the Kermadec Islands. It is red or orange in colour with coloured bands on the legs and patches on the body.
Paguristes eremita, the eye spot hermit crab, is a species of hermit crab in the family Diogenidae. It is found in the Mediterranean Sea.
Calcinus laevimanus is a species of hermit crab in the genus Calcinus found in the Indo-West Pacific region, the type locality being Hawaii. It is also known as the blue-eyed hermit crab, zebra hermit crab, dwarf zebra hermit crab, left-handed hermit crab, Hawaiian reef hermit and other similar names.
Coenobita rubescens is a species of terrestrial (land-living) hermit crab, family Coenobitidae.
Ozius deplanatus, commonly known as the black finger crab and the iron crab, is a species of crab found in New Zealand and Australia.
Coenobita pseudorugosus is a species of terrestrial hermit crab, family Coenobitidae.
