Early ammonia release by a polychaete nereis virens and a crab carcinus maenas in diluted sea water

Abstract

1. Specimens of the polychaete Nereis virens that had been kept in sea water (SW) of 30–32% salinity were placed directly in diluted sea water of one-half that salinity (S/2), and the rates of release of ammonia (NH 3) and free amino acids (FAA) were determined by analyzing the water at 0·5, 1·0, 2·0, 3·5 and 5·0 hr. 2. Specimens of the shore crab Carcinus maenas were treated in a similar manner, and NH 3 and FAA of their media and blood were determined at 2, 4 and 6 hr. 3. The rate of NH 3 release by Nereis in S/2 was 1·34–3·40 times the release by animals in SW; no FAA release was detected. 4. The rate of NH 3 release by Carcinus in S/2 was the same as controls at 2 hr, but 1·75 and 1·65 times control rate at 4 and 6 hr; FAA release was less than 10% of the rate of NH 3 loss, and did not vary significantly with time or salinity; average blood concentrations of FAA were near 11 mM and blood NH 3 1·6 mM, and did not differ significantly in the two groups. 5. The results suggest that increased NH 3 excretion is part of the early response to hypo-osmotic stress in both species, that increased FAA release does not occur, and that movement of FAA from cells into body fluids is not part of the early response in the crab.