Carcinisation

Carcinisation (or carcinization) is a hypothesised process whereby a crustacean evolves into a crab-like form from a non-crab-like form. The term was introduced by L. A. Borradaile, who described it as "one of the many attempts of Nature to evolve a crab".

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Carcinisation is believed to have occurred in at least five groups of decapod crustaceans, independently, most notably king crabs which most scientists believe evolved from hermit crab ancestors (there is still some debate over this point). The other examples are the family Porcellanidae, or porcelain crabs; these are closely related to squat lobsters, Lomis, Birgus latro, and the Brachyura itself (true crabs) ^[1].

The example of king crabs (family Lithodidae) evolving from hermit crabs has been particularly well studied and, although some doubt this theory, there is considerable evidence in its favour. For example: most hermit crabs are asymmetrical, so that they fit well into spiral snail shells; the abdomens of king crabs, even though they do not use snail shells for shelter, are also asymmetrical.

References

• McLaughlin, P A & R Lemaître (1997). Carcinization in the Anomura - fact or fiction. 1. Evidence from adult morphology. Contributions to Zoology 67: 79–123.
• McLaughlin, P A, R Lemaître & C C Tudge (2004). Carcinization in the Anomura - fact or fiction. 2. Evidence from larval, megalopal and early juvenile morphology. Contributions to Zoology 73.

1. ^ Morrison, C L, A W Harvey, S Lavery, K Tieu, Y Huang & C W Cunningham (2001). Mitochondrial gene rearrangements confirm the parallel evolution of the crab-like form. Proc. Roy. Soc. Lond. B 269: 345–350.