Indirect evidence indicates female semiochemicals release male precopulatory behaviour in the snow crab, Chionoecetes opilio (Brachyura: Majidae)

Experiments were conducted in aquaria to test the hypothesis that females of the snow crab, Chionoecetes opilio, release a sex pheromone to attract mates. Males exhibited significantly increased activity to water from a source aquarium containing recently-moulted pubescent females, egg-stripped multiparous females and recently-moulted immature females than to water from an aquarium containing berried multiparous females, eggs alone, adolescent males or an empty aquarium. Males without their cephalic chemoreceptors maintained low activity levels in the presence of reeently-moulted pubescent females, whereas maxilla-ablated males reacted as strongly as intact males. These findings are discussed within the context of the ecdysteroid-sex pheromone hypothesis, proposed by Kittredge et al. (1971) and Kittredge & Takahashi (1972), but subsequently rejected. We propose that ecdysteroids from both pubescent and multiparous females may elicit male search-and-clasp behaviour in C. opilio and that the reproductive biology of species used to refute the hypothesis was inappropriate to test the role of ecdysteroids as a cue in the mating process.