Control of chemically stimulated feeding behavior in sand fiddler crabsUca pugilator: Evidence for hemolymph feeding...

Uca pugilator, the sand fiddler crab, is a deposit-feeder. It feeds on exposed sand flats as the tide recedes. Feeding movements are evoked by stimulation of chemoreceptors on the dactyls. Previous studies have demonstrated that a proteinaceous factor associated with the sinus gland region inhibits chemically-stimulated feeding behavior. Here, that work is extended to show the existence of a similar inhibitory factor present in the hemolymph of fed crabs in the laboratory and in the hemolymph of crabs returning from feeding in the field. The factor is not detected in fasted laboratory crabs or in field crabs walking from burrow areas to feeding sites. Injection of glucose results in inhibition of feeding activity in intact crabs. Injection of glucose, but not galactose, stimulates feeding in eyestalk-ablated crabs. We suggest that neural responsiveness is stimulated by glucose, and that elevated glucose in intact crabs results in release of feeding inhibitory factor from the sinus gland. Release of feeding inhibitory factor into the blood enables crabs to return to burrow areas without stopping when they encounter food-laden sediments.