Beta-Alanine and other free amino acids during salinity adaptation of the polychaete Nereis japonica

The free amino acid pool was measured in the body wall muscle and in coelomic cells (eleocytes) of the polychaete Nereis japonica following adaptation to salinities between 6 and 44 per thousand. Beta-Alanine and glycine were the major amino acids comprising 35-60% of the total free amino acid pool in the body wall. In eleocytes, glutamate and lysine in addition to beta-alanine and glycine were the dominant free amino acids. In the body wall, the concentrations of beta-alanine were closely correlated with the ambient salinity between 12 and 35 per thousand. The concentrations of glycine rose initially but remained unchanged at concentrations above 26 per thousand. In both body wall and eleocytes, the mean total primary amine concentrations were correlated with the ambient salinities between 12 and 35 per thousand. The sum of amino acids determined by HPLC showed the same correlation in both tissues, but accounted only for 60-85% of the concentrations of total primary amines. The total protein content of the body wall was slightly higher at 44 per thousand compared to the lower salinities indicating dehydration of the tissues. Eleocytes swell at 6 per thousand and showed irregular amino acid concentrations indicating a loss of metabolic integrity.