CHRISTOPHER, CATHERINE E..*; SALMON, MICHAEL; Florida Atlantic University, Boca Raton; Florida Atlantic University, Boca Raton: Do Fiddler Crab Larvae Show Phenotypic Plasticity?

In fiddler crabs, larval release typically occurs at flood tide or shortly thereafter. The larvae are then transported by tidal currents out of the adult habitat, toward deeper �nursery� areas. When eggs are removed from a female a few hours before larval release is scheduled, they still hatch at high tide though the rhythm is less precisely synchronized with the tides. These findings suggest that both the female and her clutch have a tidal rhythm and that both play a role in the timing of the hatching and release process. The purpose of this study was to determine whether the timing of the rhythm in fiddler crab larvae was phenotypically plastic, that is, could be altered by signals from the female. To find out, eggs scheduled to hatch with 24-48 h were reciprocally transferred between ovigerous crabs (Uca thayeri Rathbun) whose clutches would hatch on the same day. Exchanges were made between females from Florida�s East coast, that release their larvae during nocturnal high tides, and females from Florida�s West coast, that release their larvae during the afternoon high tides. The data show that females released both the transplanted larvae and their own larvae at the same time, and on a temporal schedule appropriate to the females� coastal location. These results indicate that the larvae are phenotypically plastic, and will respond to signals from females to hatch several hours earlier (East coast larvae) or later (West coast larvae) than expected.