Anaerobiosis: A Possible Source of Osmotic Solute for High-salinity Acclimation in Marine Molluscs

Abstract

1. When stressed with high-salinity exposure, cell volume is restored in ventricles of Modiolus demissus demissus by a rapid accumulation of intracellular free amino acids. 2. Although the total amino acid pool increases and remains at a constant high level thereafter, the pattern and time course of accumulation is different for each major amino acid (glycine, alanine, taurine, and proline). 3. Initially, cell volume is restored by a rapid accumulation of alanine, but later its concentration decreases while glycine and taurine accumulate. Although at first not detected, the proline concentration increases, peaks and subsequently disappears again. 4. Isolated ventricles recover normal activity after large environmental salinity increases. 5. During recovery the intracellular free amino acid changes in isolated ventricles are similar to the initial pattern of accumulation in whole animals, i.e., alanine, and to a lesser extent, proline and glycine accumulate. 6. Finally, isolated ventricles undergo a period of decreased oxygen consumption on exposure to an increased salinity. 7. These results suggest that the initial stages of high-salinity acclimation in molluscs depends upon the synthesis of amino acids via a known anaerobic biochemical pathway. Note: Contribution No. 33 from the Tallahassee, Sopchoppy and Gulf Coast Marine Biological Association.