Seasonal variations in chemical response to conspecific scents in the spotted spiny lobster, Panulirus guttatus

Abstract

Chemical response to conspecific scents mediate aggregations in some species of spiny lobsters, but patterns of codenning of adult lobsters in their natural habitats vary widely. This is so for Panulirus guttatus, a small, sedentary, obligate reef‐dwelling species with a protracted, almost year‐round reproductive season. We hypothesised that changes in patterns of aggregation may vary with the intensity of reproductive activity in the population, which in turn may cause changes in responses to conspecific scents. To test this hypothesis, we conducted three laboratory experiments with Y‐mazes to test for seasonal variations in gender‐related and size‐related response to conspecific scents in mature P. guttatus. When reproductive activity (RA) was high (experiment High‐RA, 67.4% reproductive females), males responded significantly to scents of conspecifics of both genders, but females only to the scent of females. When reproductive activity had not yet reached its yearly lowest point (experiment Medium‐RA, 50.0% reproductive females), only females responded significantly to scents of other females, and when reproductive activity was at its lowest (experiment Low‐RA, 4.8% reproductive females) no treatment yielded significant responses. However, results of the size‐related treatments showed that only large individuals responded significantly to scents of other large lobsters during the High‐RA experiment, whereas during the Medium‐RA only small individuals responded to scents of both small and large lobsters. These results are in accordance with previously observed size‐dependent reproduction in P. guttatus over the protracted reproductive season. Therefore, chemical response to conspecific scents in P. guttatus vary with season, gender, and size and may influence co‐denning patterns of mature individuals in the reef habitat.