Meeting Abstract

29.5  Friday, Jan. 4  Cost of Living Differences Among Fiddler Crab Populations Along a Tidal River. BORGIANINI, SA*; SPROUL, G; FLENNIKEN, MM; SUTTON, MC; BRODIE, RJ; University of South Carolina; University of South Carolina Beaufort; Ht. Holyoke College; University of South Carolina Beaufort; Ht. Holyoke College borgians@biol.sc.edu

The bioenergetic cost of osmotic stress is often expressed in reduction of energy reserves available for growth and reproduction. Large populations of red-jointed fiddler crab, Uca minax (LeConte, 1855) have been observed all along the Winyah Bay estuary in South Carolina. Upriver populations live their entire juvenile and adult lives in freshwater and are able to reproduce successfully reproduce even with the presumed increase in energy expenditure required for osmoregulation. In order to assess the possible bioenergetic cost of occupying upriver freshwater habitats versus brackish water habitats, we examined both size and fecundity in crabs from upriver and downriver populations. Ovigerous U. minax females were collected from two sites on three occasions shortly before peak nocturnal spring tides when hatching of zoea larvae typically occurs. Size and fecundity were examined by measuring adult female dimensions, brood size and zoeal lipid content. Based on preliminary data female carapace width, and width/length ratios were found to be statistically different between the two locations, with the upriver population containing larger, boxier crabs. Brood size and individual zoeae dry weight differences were not found to not be significantly different between the two populations. Size differences between the populations remained consistent even when the investigation was expanded to include both males and females. Qualitative and quantitative results of zoeal essential lipid content were also examined by GC/MS analysis of fatty acid methyl esters in order to determine if females of the two populations provisioned their offspring differently.