On a recent trip to St. Vincent (West Indies) my sons Kris and Keri documented a crab that we'd never seen before. We couldn't tell from the photos and videos whether or not it was a known species, so I went back to St. Vincent with my wife and collected some specimens. The analysis showed it to be Thersandrus compressus, a spider crab that lives on (and eats) the alga Avrainvillea longicaulis. This alga looks like a green spatula with the handle stuck in the sand, and it's "everywhere". But have you ever seen this crab? It flattens itself against the leaf and blends in so well that it could be right in your face and you won't see it. Very little is known about this crab. Only a few specimens exist in collections --- the Smithsonian's most recent specimen was collected in 1914.
Next time you're diving in the Caribbean, why not check out those algae plants. If you find this crab, please let me know. I'm trying to get distribution information for it.
Les Wilk
