Meeting Abstract
P3.151 Wednesday, Jan. 6 Now you see it, now you don’t: the effects of salinity and temperature on the transparency of the ghost shrimp, Palaemonetes pugio BHANDIWAD, AA*; JOHNSEN, S; Northeastern University, Boston, MA; Duke University, Durham, NC bhandiwad.a@neu.edu
The ghost shrimp, Palaemonetes pugio, is a detritivore that plays a major role in nutrient recycling and is a primary consumer in Atlantic and Gulf coast estuarine systems. These systems experience rapid changes in salinity and temperature due to tidal cycles, evaporation, and runoff. Because P. pugio faces high predation pressure from visual predators such as killifish (Fundulus heteroclitus), summer flounder (Paralycthys dentatus), and post-larval decapod crustaceans, it is thought that its transparency has evolved to serve as a form of crypsis. In this study, we examined the effects of rapid, but ecologically relevant, changes in salinity and temperature on the transparency of P. pugio under laboratory conditions. Animals normally kept at a salinity of 15 ppt and a temperature of 20º C were placed into solutions with salinities of 0, 15, 25 or 30 ppt and temperatures of 12º C, 20º C, or 28º C for 12 hours. We found that at the control conditions of 15 ppt at 20ºC (N = 43), 64% + 2.8% (Mean+SE) of incident light was transmitted through a 2 mm thickness of the tail muscle, whereas at the extremes of 30 ppt at 28º C (N = 10) and 30 ppt at 12º C (N = 29), the light transmission was only 0.03% + 4.0% and 4.5% + 2.8%, respectively (ANOVA, F=57.6, p < 0.0001). Though both were significant, the effects of temperature were more pronounced than the effects of salinity. We believe that this loss of transparency is due to pooling of low index hemolymph between the high index muscle fibers, which increases light scattering. This induced opacification increases the visibility of the animal and thus may increase predation pressure during periods of salinity and temperature change, changing estuarial trophic dynamics and infaunal composition.
