A number of lineages of crabs have evolved to live predominantly on land. Examples of terrestrial crabs are found in the families Gecarcinidae and Gecarcinucidae, as well as in selected genera from other families, such as Sesarma, although the term "land crab" is often used to mean solely the family Gecarcinidae.
Terrestriality and migration
There is no clear distinction between "terrestrial", "semi-terrestrial", and "aquatic" crabs. Rather, there is a continuum of terrestriality displayed among the true crabs, although most land-adapted crabs must still return to water to release their eggs. Some species of terrestrial crabs can be found many kilometres from the sea, but have to complete annual migrations to the sea. For example, following the Indian Ocean monsoon, the Christmas Island red crab (Gecarcoidea natalis) migrates en masse, forming a "living carpet" of crabs. The crabs can travel up to 1.46 km (0.91 mi) in a day, and up to 4 km (2.5 mi) in total. Only a few land crabs, including certain Geosesarma species, have direct developement (the mother carries the eggs until they have become tiny, fully developed crabs) and these do not need access to water to breed.
Terrestrial crabs have often evolved from freshwater crabs, since the physiological changes needed for living in fresh water are pre-adaptations for terrestrial living. On some oceanic islands, terrestrial crabs occupy the top of the energy pyramid.
- Freshwater crab
- Coenobitidae, the terrestrial hermit crabs
- Coconut crab (Birgus latro), a terrestrial hermit crab which is the largest terrestrial invertebrate in the world
- Richard G. Hartnoll (1988). "Biology of the land crabs: an introduction". In Warren W. Burggren & Brian Robert McMahon. Evolution, systematics, and geographical distribution. Cambridge University Press. pp. 6–54. ISBN 978-0-521-30690-4.
- Warren W. Burggren & Brian Robert McMahon (1988). "Biology of the land crabs: an introduction". In Warren W. Burggren & Brian Robert McMahon. Biology of the Land Crabs. Cambridge University Press. pp. 1–5. ISBN 978-0-521-30690-4.
- Colin Little (1990). "Life on land". The Terrestrial Invasion: an Ecophysiological Approach to the Origins of Land Animals. Cambridge studies in ecology. Cambridge University Press. pp. 201–275. ISBN 978-0-521-33669-7.
- Ben Hoare (2009). "Red crab". Animal Migration: Remarkable Journeys in the Wild. University of California Press. pp. 74–75. ISBN 978-0-520-25823-5.
- Burggren, W.W.; McMahon, B.R., eds. (1988). Biology of the Land Crabs. Cambridge University Press. pp. 53–54. ISBN 978-0521306904.
- Tan, C.G.S.; Ng, P.K.L. (1995). "Geosesarma notophorum sp. nov. (Decapoda, Brachyura, Grapsidae, Sesarminae), a Terrestrial Crab from Sumatra, with Novel Brooding Behaviour". Crustaceana. 68 (3): 390–395. doi:10.1163/156854095X00557.
- Michael Dobson (2004). "Freshwater crabs in Africa" (PDF). Freshwater Forum. 21: 3–26.
- Encyclopedia Americana. 1920. .