RESPONSE OF MUD CRAB (PANOPEUS-HERBSTII) MEGALOPAE TO CUES FROM ADULTHABITAT

During the summer of 1995, we investigated the response of mud crab me galopae (Panopeus herbstii Milne-Edwards) to cues associated with adul t habitat. Natural rock/shell substratum and the rock-associated seawe ed, Fucus vesiculosus L., both induced metamorphosis of competent mega lopae; natural sand substratum did not induce metamorphosis. Structura l mimics of preferred substratum induced metamorphosis only when cover ed with natural biofilm. Clean mimics dib not induce metamorphosis. Wa ter-soluble exudates from preferred substrata showed weak induction of metamorphosis. Exudates from adult P. herbstii elicited a similar wea k response. Exudates from another species of crab and from two fish pr edators did not induce metamorphosis. We conclude that water-soluble c ues associated with major components of preferred adult habitat induce the metamorphic molt of P. herbstii megalopae. The three-dimensional structure of the substratum is not important in induction of metamorph osis, but the biofilm associated with preferred substratum plays a cri tical role. It is not clear whether the biofilm produces the water-sol uble cue or simply provides a tactile stimulus that works in conjuncti on with the soluble cue.