18 Dec 2007

FSL: Fiddler Sign Language

Dear Blue Lobster:

so wat can u tell me abt fiddler crab sign language?


Dear Gentle Sir:

Fiddler crabs (Uca sp.), known for the male's oversized claw, communicate by a series of complex movements and gestures. It is thought that Fiddler sign language, or FSL, developed around the same time the oversized claw and associated mating rituals did, some twenty to twenty five million years ago.

Despite the relatively high level of communication, one Uca species can not understand the other's sign language. For the Uca genus, this dictates speciation as two physiologically identical species, such as U. volens and U. spiralis, will not breed or cohabit with one another. Thus signal communication dictates that the two will eventually drift further physically like other, less distantly related species like U. hoh and U. vula.

The lack of communication between species leads to unique behavior in Uca where one species will not only defend their territory from another but will attempt to completely wipe out neighboring Fiddler crabs. Typically one species signs are interpreted as offensive to another, with one study showing an increase in circulation and pheromones when crabs of different species were exposed to one another. In nature this results in different Uca species seeking to wipe out others until only one remains dominant on the beach, allowing for interspecific combat thereafter.

This crustacean genocide is thought to serve as a means of increasing the chances of successful breeding. With up to fifty percent of Fiddler populations reduced during breeding season from predation by fish, bird, monkeys, other crabs, and humans, population density is one way to ensure successful reproduction.

FSL isn't as complex as human sign languages, of course. Fidders, for instance, have no concept of the past or a past tense in their signs. Everything happens in the present tense for a Fiddler. This includes the immediate future. For example, a herd of Fiddlers will begin signing for food as soon as they detect an appropriate scent and will continue this gesture throughout the course of the meal. Likewise females sign for pregnancy before eggs are visible and continue until their young are newly hatched.

Research into the origin and development of FSL continues. A tentative family tree based on similarities and differences in FSL is being worked out, and research at National University in Australia hopes to link it to a molecular data family tree.