Meeting Abstract
6.6 Jan. 4 Salinity Tolerance and Osmotic Response of the Estuarine Hermit Crab Pagurus maclaughlinae in the Indian River Lagoon, Florida RHODES, S/E*; TURNER, R/L; Florida Institute of Technology; Florida Institute of Technology rturner@fit.edu
Pagurus maclaughlinae is the most common hermit in the Indian River Lagoon. Wide variations in salinity make it likely that P. maclaughlinae is euryhaline and that other hermit species in the area are stenohaline, at least in some stages of their life histories. In a study of salinity tolerance, crabs were held unfed at salinities of 5–50‰ (25‰ control) for up to 30 d. Based on LT50s, P. maclaughlinae tolerated acute exposure to salinities of 10–45‰ for up to 18 d, and survivorship up to 30 d at 20–45‰ equaled or exceeded survivorship of the control. In a study of acclimation, the osmotic pressure of hemolymph was measured after crabs were held in the laboratory for 12, 48, and 96 h acutely exposed to salinities of 10–45‰. Paired t-tests revealed that the crabs weakly hyperregulated their hemolymph at 45–154 mOsmol above the external medium at all salinities and sampling times. In a third study, acclimatization of hemolymph was studied on crabs at four field sites that differed in their recent salinity histories. Field-collected crabs weakly regulated their hemolymph 72–84 mOsmol above the external medium at all sites sampled. Performance did not differ by site. The broad range of salinity tolerance in this crab explains their wide distribution, and the consistent osmotic differential of its hemolymph indicates that the osmoregulatory ability of this species is conserved in populations throughout the lagoon. Although some other hermit species in the region are euryhaline as adults, their tendency to hyperregulate strongly at low salinities possibly adds an energetic burden that, along with their stenohaline larvae, excludes them from the lagoon. Salinity tolerance of larval P. maclaughlinae has yet to be studied.
