Meeting Abstract

101.1  Wednesday, Jan. 7  Where Did You Get That Rhythm? Plasticity in the Circatidal Swimming Behavior of Fiddler Crab Larvae LOPEZ-DUARTE, P.C.*; TANKERSLEY, R.A.; Scripps Institution of Oceanography; Florida Institute of Technology plopezduarte@ucsd.edu

Fiddler crab Uca pugilator larvae (zoeae) possess an ebb-phased circatidal rhythm in vertical swimming that matches the period of the local tidal regime (~12.4 or 24.8 h) and facilitates export from estuaries to offshore development areas. We tested the hypothesis that the rhythm exhibited by U. pugilator zoeae is phenotypically plastic and entrained in embryos prior to hatching. To test whether developing embryos receive tidal information from cues associated with the adult habitat, ovigerous females were reciprocally translocated between beaches with diurnal and mixed tides. To test the alternative hypothesis that tidal information is communicated from mother to embryos during incubation, egg clusters were exchanged between crabs from areas with semidiurnal and diurnal tides. Swimming activity of transplanted zoeae was compared to that of larvae from the original (donor) and recipient (surrogate) egg masses. Vertical swimming activity was monitored under constant conditions for 72 h using a time-lapse video system. Larvae from female crabs translocated between beaches possessed ebb-phased circatidal rhythms that matched the dominant period of the tides at the original (native) beach. However, larvae from egg clusters exchanged between crabs from different beaches possessed circatidal rhythms that differed significantly from those exhibited by larvae from the original (donor) egg mass. These results suggest that the period and phase of the circatidal rhythms exhibited by U. pugilator zoeae are not influenced by environmental conditions prior to hatching, but instead are the result of some unknown interaction or communication between the female and embryo during brooding.