Mate recognition in a simultaneous hermaphroditic shrimp, Lysmata wurdemanni (Caridea: Hippolytidae)

Abstract

Male crustaceans must find and identify receptive females to mate successfully. Sex recognition depends mainly on sex pheromones, which are detected by antennae and antennules. Distance (soluble) pheromone mediates mating behaviour of some decapod crustaceans. Contact pheromone (an insoluble coating on the body surface) has been proposed but not confirmed to be used by male decapod crustaceans to detect females. Here we report for the first time the involvement of both distance and contact pheromones in the mating processes of a decapod crustacean, Lysmata wurdemanni, a protandric simultaneous hermaphrodite. Euhermaphrodite-phase (EP) shrimp can mate only as females during the small window of the postmoult period, during which they secrete both distance and contact sex pheromones to attract males. Male shrimp tracked, recognized and courted the receptive EP shrimp based on both distance and contact sex pheromones, but responded aggressively to newly moulted male shrimp. Male shrimp with their chemosensory appendages ablated appeared unable to identify EP shrimp and neither courted nor copulated with them. As reported for other decapod crustacean species, the outer flagella of the antennules house the receptors of the distance pheromone, whereas both antennae and antennules can detect the contact pheromone. Shrimp could still mate successfully without the distance pheromone. These results suggest that contact pheromone, in addition to distance pheromone, is involved in mediating the mating behaviour of L. wurdemanni. Moreover, contact pheromone may be more important than distance pheromone in the mating process. Selection of the sex pheromone system of L. wurdemanni may be driven by social environment.