Rudi Diesel expounds on the "snail-shell crab" at Windsor in June, 2000. He has been studying these crabs in Jamaica since 1986 and is presently preparing a video presentation on Cockpit Country research. The "snail-shell crab" (Sesarmae jarvisi) is an example of special adaptation to the "waterless" karst terrain and a remarkable example of "brood care" in the Cockpit Country. The females raise their families in the shells of dead snails. They actually turn the shell over to put the aperture downwards so that rain and dew does not flood their "house". They then carry dew water to fill the shell up to its overflow so that the larvae (which still have gills) can survive. Of course, as Rudi says (see Bibliography), the first remarkable adaptation of these crabs was to learn to live in fresh water instead of their original salt water. no doubt this occurred during the millions of years when Jamaica slowly submerged and then reemerged from the sea (see Formation of Jamaica). Another example of brood care Rudi discovered is the bromeliad crab (Metopaulias depressus), which raises its young in the water-filled bromeliads. The mother manipulates water quality by removing detritus , circulating water to oxygenate it and carrying empty snail shells into the bromeliad as both a calcium source and a pH buffer.
Molecular evidence shows that Jamaican land crabs evolved from a single adaptive radiation from a marine ancestor that invaded terrestrial habitats only 4 million years ago (Schubert et al, Nature vol 393, 28May,98 see Bibliography), so that it is possible that M. depressus should be placed in the same genus as the other Jamaican endemic crabs, of the genus Sesarma.

Rudi is based at the Max Planck Institute in Germany and you can check out his excellent site at

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