Christopher, Catherine E.

Larval release by adult fiddler crabs occurs during the ebbing tides, but its timing
relative to the day-night and tidal amplitude cycles depends upon tidal form (e.g., shows
phenotypical plasticity). Crabs (Uca thayeri) from Florida's East Coast are exposed to
semidiurnal tides and release their larvae at night, whereas crabs from Florida's West
Coast exposed to mixed tides release their larvae during the afternoon. The purpose of
this study was to determine whether the larvae could hatch at times other than those
correlated with the tidal form at their location. Clusters of eggs at similar stages of
development, 24-72 h in advance of release, were reciprocally transferred between
females from each coast. Release ofboth the transferred larvae and maternal clutch
occurred synchronously, and at the time dictated by the female's tidal regime. These
results suggest that larvae are phenotypically plastic with respect to hatching time and
can either delay (West coast) or advance (East coast) their response to release signals
from females.