ANAEROBIC METABOLISM IN SUBLITTORAL LIVING MYTILUS-GALLOPROVINCIALIS IN THE MEDITERRANEAN .4. ROLE OF AMINO-ACIDS IN ADAPTATION TO LOW SALINITIES DURING ANAEROBIOSIS AND AEROBIOSIS

1. When Mytilus galloprovincialis were transferred from 38 to 19 parts per thousand sea water (S), the metabolism became anaerobic for at least 8 hr. After 24 hr the animals were entirely aerobic again. 2. Upon transfer to 19 parts per thousand S, the total free amino acid concentration in haemolymph doubled within 4 hr, remaining nearly constant thereafter, up to 48 hr. 3. In the posterior adductor muscle a strong decrease of alanine and glycine occurred at 48 hr exposure to 19 parts per thousand S, and a smaller decrease of glutamate; taurine remained relatively constant. When transferred again to 38 parts per thousand S after 14 days, a strong overcompensation occurred in the concentrations of alanine and proline, and a smaller overcompensation in those of threonine and serine. 4. In the gill no distinct change in the amino acid pool occurred during 14 days of exposure, with the exception of a decrease in serine. When transferred again to 38 parts per thousand S, a strong overcompensation occurred in alanine, proline, glycine and serine, and a smaller in glutamate and threonine. 5. No evidence for anaerobic metabolism in the decrease of the amino acid pool was found. 6. M. galloprovincialis is less able to adapt to low salinities than the more euryhaline M. edulis.