GIRI, T*: Chemical detection of reproduction condition by the hermaphroditic shrimp Lysmata wurdemanni

In the caridean shrimp Lysmata wurdemanni, individuals are initially male but with increasing age become simultaneous functional hermaphrodites. Larger individuals in a population are therefore able to mate as either males or females. Although mating as a “male” can occur throughout the moult cycle, individuals reproduce as “females” when vitellogenic oocytes are present in the ovotestis and only during a brief period immediately following moulting. Male-phase individuals must therefore discriminate amongst potential partners if they are to mate with freshly-moulted individuals of appropriate reproductive condition. This study examined if L. wurdemanni can perform this discrimination using chemical cues. Stimulus solutions were collected from freshly moulted male-phase individuals (MP), female-phase individuals with no oocytes (FP0), and female-phase shrimp with vitellogenic oocytes present (FP4). L. wurdemanni were placed in a square testing tank and presented with a stimulus or control solution slowly pumped to each of the four corners. Recordings were made of the time spent in the area immediately surrounding each stimulus entry point, and also of any grasping actions performed by the test animal within these zones. L. wurdemanni spent a greater amount of time near the FP4 stimulus source than in any of the other three zones. In addition, the vast majority of physical manipulations were performed towards the stimulus apparatus used to pump FP4 solutions. These results indicate L. wurdemanni is able to chemically discriminate among potential mating partners.