Impacts of biochemical cues on horizontal swimming behavior of individual crab larvae

Abstract

To determine if larval crabs alter their horizontal swimming behavior in response to biochemical cues in the water, fiddler crab (Uca pugnax) and blue crab (Callinectes sapidus) megalopae were video recorded in a laminar-flow flume while putative cues were introduced and allowed to establish a gradient in the flow field. Changes in horizontal orientation, distribution, and swimming velocity were observed for six different cue treatments. Overall results show that crab megalopae can detect biochemical cues in ambient water and that they adjust their horizontal swimming behavior in response to these cues. The dominant response was a change in swimming velocity in the presence of a cue. While this response may affect the dynamics of larval patches, it is not clear if swimming in the horizontal plane has a substantial effect on the spatial aggregation of the larvae in the field.