by M. Kathy Raines

Crabs here! Crabs there! Fiddler crabs everywhere! This July, I gingerly threaded my bicycle through ranks of skittering crabs—each male lugging a massive claw— on the Brownsville Historic Battlefield Trail after a soaking from Hurricane Hanna.

Colonies of Laguna fiddler crabs (Uca (Leptuca) sybcylindrical), with adjacent pebbly palaces, can live miles inland, far from all but ephemeral puddles. Only this robust fiddler—one of our county’s six species— thrives in a semi-arid habitat. It digs deep into salty groundwater, its mottled gray carapace camouflaged against dirt and gravel. It also flourishes in the highly saline Laguna Madre. It ranges roughly from Galveston to Tampico.

Fiddler crabs are small, their carapaces, or shells, rarely over two inches in diameter. Only the male fiddler bears an oversized cheleped, or claw-bearing limb, which it waves to attract mates and defend turf. Unlike most invertebrates, fiddler crabs are territorial, brandishing their claws at would-be usurpers, but rarely fighting. Nevertheless, this claw can pierce a rival. A male may lose his claw, which soon regenerates on its opposite side. It is smaller and weaker. Nevertheless, its owner feigns that it is grand and dangerous.

The name “fiddler crab” apparently derives from the male’s claw-waving which resembles a violinist. Many Spanish-speakers call it “Cangrejo” (crab) violinista”, but Peruvians, its movement evoking a needle worker, call it “maestro sastre” or “master tailor”. Both Brazilians and Japanese, imagining the crab’s signaling to the sea, call it, respectively, “Chama mares”—literally “call seas”, and, “Siho maneki” for “beckoning for the return of the tide.” Also, some English speakers designate it “calling crab”. 

Birds and other creatures relish these delectable morsels. I’ve seen crabs crushed within meadowlarks’ beaks and skewered on yucca spears—victims of the notorious loggerhead shrike. With its long bill, a curlew scoops the crab out of its nearly six-foot burrow.  

This crab dines on decayed matter—nematodes (unsegmented worms), fungi, algae and bacteria. While the female eats with two claws, the male—his huge claw ill-adapted to this task—utilizes one. 

The crab delivers a tiny clump of sand to a front set of scissoring, hair-fringed blades, one of which flicks edible morsels into the mouth, while another holds onto the rest. From the waste, the crab forms a pellet, which it dumps into a pile. Then it spoons in more sand. Pellets accumulate into drip castles. 

The crab functions outside of water, providing its gills remain damp. It retains water in its gill chamber, which it renews by churning water through its mouthparts, whipping it into an oxygen-rich froth.

Waving its cheliped, the male entices a female into his L-shaped burrow to mate. If interested, she complies. Evidently, females prefer a large, vigorously waving claw, which indicates a hardy crab with a large burrow for breeding. 

She incubates her sponge (eggs) for about two weeks, then releases microscopic, free-swimming larvae into water. In an apparent adaption to our dry climate, the crab’s larval development is abbreviated. Larvae grow into crabs in less than two weeks, before puddles evaporate. 

A thriving population of fiddler crabs indicates a healthy ecosystem, as they are sensitive to pesticides and heavy metals. Also, as they dig, they aerate soil.

Originally published: https://issuu.com/digitalpublish/docs/south_padre_parade_november_2020/s/11188966