9-Pound Crab Has Bug's Nose

The robber crab, Birgus latro, is the world's largest land-dwelling arthropod, with a weight of nine pounds and a length of nearly two feet.  It is famous for climbing tall palm trees in search of coconuts, which it can crack open with its massive claws.

In leaving its marine ancestry behind, robber crabs have evolved to such a degree that they would drown if submerged in water.  Among the many adaptations induced by this transition, the crab's sense of smell was altered by the very different demands of an air medium.

Marcus Stensmyr from the Swedish University of Agricultural Sciences and his colleagues have found that the olfactory system of the robber crab resembles - functionally, behaviorally, and structurally - that of insects.

This is a striking example of convergent evolution, where distantly related organisms come up with similar strategies for surviving in the same environment.

These results were published in this week's issue of Current Biology.

-- LiveScience Staff

Credit: Marcus Stensmyr & Bill S. Hansson