Chemical and live feeding stimulants of the sand fiddler crab, Uca pugilator (Bosc)

Abstract

The feeding responses of the sand fiddler crab, Uca pugilator (Bosc), to various chemical and living food sources were determined using sand substrates. The only amino acids to elicit feeding were in order of preference : l-serine, l-alanine, l-asparagine and l-glutamic acid. A variety of sugars elicited feeding including insoluble dextrin. Sucrose and maltose, the most stimulatory sugars, were more stimulatory than l-serine. Synergistic interactions were observed in the stimulatory capacities of amino acids, amino acids + sugars, and living organisms. Diatoms, blue-green algae, and bacteria elicited feeding responses, but bacteria appeared to be less stimulatory than diatoms. Ciliates in themselves produced a weak feeding response, but they significantly increased the palatability of l-serine solution. The spectrum and threshold concentrations of chemicals which elicit feeding in U. pugilator are different from those of previously studied marine Crustacea. These differences are interpreted as resulting from adaptations to different food-limited foraging environments. Most previously studied Crustacea forage underwater on large parcels of fleshy food whose availability is limited by the distance between parcels. Sand fiddlers feed primarily out of water on benthic microorganisms whose availability is relatively unlimited in space but is limited by the time available for foraging by sand Fiddlers.