The effects of fluctuating salinity on protein profiles in echinoderm larvae of the species Dendraster excentricus and Pisaster ochraceus

Abstract

Salinity fluctuations are common in the Salish Sea of the Pacific Northwest and are expected to become more common as global warming continues to increase the rate of glacial melting. The salinity can drop down to as low as 20‰ from the normal level of 30‰ in these fluctuations which usually occur during the summer months when many marine invertebrates are reproducing. Especially affected are echinoderms since they lack the ability to osmo- or ionregulate. In this study we investigated the effects of fluctuating salinity on protein expression in larvae of the sand dollar Dendraster excentricus and the seastar Pisaster ochraceus. Adults were spawned and larvae were reared in 2 treatments: control (constant salinity of 29-30‰) and fluctuating salinity (FS, salinity dropped to 21‰ for 2 day periods every ~7 days). Samples were taken periodically, analyzed for protein content by the Bradford Assay, and separated by SDS PAGE to look for differences in banding patterns. A number of differences in protein expression were discovered in both P. ochraceus and D. excentricus larvae exposed to fluctuating salinity but the exact identity of these proteins are not known until mass spectrometry is completed. The proteins that differed likely function in metabolism, skeletogenesis, ion transport, or muscle growth.