Responses to single and multiple sources of chemical cues by New Zealand crustaceans

This study examined the patterns of responses shown by animals to the simul taneous detection of conflicting inputs. The responses of individuals of se ven species of New Zealand crustaceans to the introduction of alarm odours were tested in the laboratory. The crayfish Paranephrops zealandicus spent more time in the lowered posture while four species (Petrolisthes elongatus , Halicarcinus innominatus, Notomithrax ursus, and Cyclograpsus lavauxi) de creased locomotion or other movements upon introduction of alarm odour. The hermit crab Pagurus novazealandine increased the frequency of shell grasps while Pagurus traversi showed no change in any behaviour. Combinations of two odours (alarm+food or alarm+shell cues) were presented to five species. The pattern of responses could be categorized as either a domination of one response over the other (Pagurus traversi, P. novazealand iae, and Halicarcinus innominatus) or an intermediate level of response com pared to those shown to single stimuli (Paranephrops zealandicus and Petrol isthes elongatus). The latter pattern is correlated with the species having alternative mechanisms for predator avoidance. When individuals of Halicar cinus innominatus were exposed to alarm odour and subsequently exposed to f ood odour two and four hours later, their responses to food odour were stil l significantly decreased.