Free Amino-Acid Levels in the Coelomic Fluid and Body Wall of Polychaetes

Coelomic fluid amino-acid nitrogen (AAN) shows great variability among the fourteen polychaete species examined, ranging from about 1 to 5 mg./l00 ml. in subtidal species to more than 150 mg./l00 ml. (about 100 mM/1.) in an intertidal species. The concentration of ammonia nitrogen (NH3 N) in coelomic fluid is roughly about 5% of the AAN. 2. Individual variation in coelomic fluid AAN normally occurs intraspecifically and possible sources of variability are considered. 3. Axial gradients exist in all species examined for this. Amino-acid concentration always increases posteriorly, and pH usually decreases in the same direction. 4. Intracellular (body-wall) AAN is relatively less variable both within and between species, the range being from about 130 mM/kg. tissue water in Aphrodite to about 400 mM/kg. in two terebellids. Concentrations do not appear to correlate with habitat. Tissue NH3 N levels are slightly higher proportionately than in coelomic fluid, and are more variable.