Effects of acute salinity stress on embryos of the sacoglossan sea slug, Alderia modesta
Intertidal organisms face highly variable environments with a multitude of stresses placed on them. Freshwater input from rain and run off is one such stress. Salinity changes have been shown to have adverse developmental effects on embryos of intertidal organisms. Although these organisms have developed different mechanisms by which larvae and embryos cope with stresses, relatively little has been demonstrated on the range of environmental stresses the eggs are able to tolerate. In this study adults and egg masses of the sacogloassan sea slug, Alderia modesta (Lovén 1844), were subjected to acute salinity stress to determine the consequences for reproduction and embryonic development to hatching, respectively. New egg masses that had been laid at constant salinity were exposed to varying salinity (7-37ppt) stress within 12 hours of deposition. Adults were exposed to varying salinity while reproducing and the egg masses they subsequently produced were compared between ambient and experimental conditions. Hatching success of eggs was significantly higher at intermediate salinities, with zero hatching success at the lowest salinity treatment (7ppt), and delayed development with low (10%) success at the highest treatment. When exposed to the same acute salinity stresses, adults did not lay egg masses so no comparative data was collected. These results show tolerance to and development in lower salinity than previous studies, providing evidence that successful reproduction might be less restricted by conditions of embryonic development.