benthic (paleo)ecology, ichnology, paleobiology
They make no music. They have no fiddle. Nevertheless, the feeding movements of the minor claw of male Uca crabs while holding their major cheliped up is somehow resemblant, or at least someone thought so, to those of a musician moving the bow of an invisible Stradivarius. Fiddler crabs abound in the muddy intertidal shores of low latitude seas and oceans of every continent except Antarctica. Almost one hundred species are known but only one of them lives in Europe. Uca (Afruca) tangeri is in fact the only fiddler crab in the eastern coast of the Atlantic extending from the shores of Angola to the southern littoral of the Iberian peninsula. In the coast of Huelva, they are known as bocas and the major claw of the male (the one holding the invisible violin) constitutes a traditional item in local gastronomy, even despite the species is today protected. Locals hunt the crabs to retrieve the cheliped without killing the animal who is able to regrow a new claw, what leads to some casual encounters with some confused machos with a tiny major claw. Females are equally handed and at least from that point of view their life seems to be easier.
I had the opportunity of spending some time with these very fascinating creatures in the last years, always accompanied by my Andalusian colleague Fernando Muñiz and my student Zain Belaústegui. It was exciting and at the same time relaxing to quietly sit in the intertidal flat during low tide and wait for the hundreds of crabs to emerge from their burrows, after accepting us as part of the landscape. We would be there, barely moving, like giant Gullivers surrounded by busy Lilliputians dedicated to their task of feeding from the sediment in a continuous, hypnotic dance. A dance that quickly transforms the upper layer of sediment from a pristine, smooth surface right when the tide goes down, to an extensive carpet of muddy pellets, riddled by multiple trackways and pierced by deep burrows.
Hopefully, I will come back to this topic in future posts. In the meantime, you may find more information on fiddler crabs of the world at http://www.fiddlercrab.info/index.html.