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1. The anemone Metridium senile survives salinities from seawater (950 mOsm) to 55% SW (520 mOsm) for at least two weeks. Animals exposed to 40% SW (380 mOsm) die within three days. 2. The tissue amino acid content of M. senile acclimated to 950 mOsm, 807 mOsm, 665 mOsm and 520 mOsm for two weeks is respectively, 444, 382, 331 and 251 μmol/g dry wt. A decrease in the concentration of taurine accounts for nearly all of the decrease in the free amino acid pool. 3. Tissue hydration increases in M. senile acclimated to dilute seawater, but the increase was not proportional to the change in ambient salinity, indicating that the anemones partially regulate volume in dilute media. 4. Mathematical analyses of changes in tissue hydration as a function of ambient salinity in M. senile , Haliplanella lineata , and Diadumene leucolena suggest that the effectiveness of volume regulation increases in individuals of these species acclimated to progressively more dilute media. The volume regulatory capability of Bunodosoma cavernata does not change in dilute media. |
