The recent identification of uridine diphosphate (UDP) as the female sex-pheromone in the European shore crab Carcinus maenas demonstrated not only the link between moult and pheromone production, but also how it may have evolved from a 'simple' metabolic byproduct. Consequently, it is expected to be present in other moulting crustaceans, thus raising issues involving species specificity of the female pheromone. Bioassays were conducted using synthetic pheromone (UDP, 10(-3)-10(-4) M) to examine if it induced sexual behaviour in other crustacean species that are neither closely related nor occur in the same ecosystem. The snow crab, Chionoecetes opilio, and the yellowline arrow crab, Stenorhynchus seticornis, both belonging to a different s...