Meeting Abstract

P2.15  Jan. 5  Intraspecific Variation in Biological Rhythms: Comparing Two Species of Fiddler Crabs From Different Tidal Regions WINSTEAD, C. R.*; THURMAN , C.L.; University of Nortnerh Iowa, Cedar Falls thurman@uni.edu

For an intertidal organism, the ocean�s ebb and flood are major factors controlling behavior. Along the southeast coast of the United States, there are four kinds of tide habitats or regimens: strictly semidiurnal; mixed-mainly semidiurnal, mixed mainly diurnal, and strictly diurnal. Does the local tide pattern determine the properties of the endogenous biological rhythm expressed by an organism? The locomotor behaviors of the fiddler crabs U. pugilator and U. minax from the Atlantic and the Gulf coasts were studied in the laboratory. After the crabs were placed in actographs, their locomotor activity was recorded in the absence of daily and tidal �zeitgebers�. The activity data was analyzed quantitatively using periodogram analysis to estimate the period length of significant rhythms. Under LL, a significant percentage of both species from the semidiurnal habitat in the Atlantic exhibit daily (12/24h), tidal (12.4h) and circalunidian (24.8h) rhythms. On the other hand, Gulf populations where strictly diurnal tides occur, the crabs were found to have a lower percent rhythmicity. In LD, Uca express a high percent rhythmicity regardless of habitat. However, tidal periods in general are missing from the actograms of the Gulf species. We conclude that daily, tidal and circalunidian rhythms are important for population of crabs from semidiurnal tidal habitats along the Atlantic. Along the northern Gulf where strictly diurnal tides occur, daily (12/24h) and circalunidian (24.8h) are more prominent in these species than tidal (12.4h) rhythms.