Chemical communication in crayfish

Abstract

Crayfish are a species rich group of large decapod crustaceans that inhabit freshwater environments. Having served as important models for the study of the neural and hormonal control of behavior crayfish were among the first crustacean taxa that were reported to use sex pheromones. Decades of research on crayfish chemical communication have, after initial controversies, now generated a comprehensive picture of the role of pheromones in resolving combats and in initiating sexual interactions. Moreover, the structures involved in chemical signal emission and reception have been identified in most cases. Urine, released in the head region, conveys the chemical messages and is directed via water movements such as gill currents or maxilliped generated currents to the receiver. Chemo-receptors on the first antennae were shown - in most cases - to be responsible for pheromone detection. Urinary signals reduce the duration of aggressive interactions and are crucial for the development of a linear dominance hierarchy. The social hierarchy is based on chemical recognition of the dominance status between combatants. Males are more active than females in initiating reproductive interactions. They recognize a female sex pheromone contained in the urine pulses that females release during the initial aggressive bout preceding mating. Female assessment of male quality is multimodal, involving tactile, visual, and in some cases also chemical cues. The recent development of context-specific and less ambiguous bioassays will facilitate the future purification of the molecules that mediate sexual receptivity and social status in crayfish. These pheromones could be valuable for application in the control of alien invasive crayfish species that cause environmental damage.