HANDLING-INDUCED CHANGES IN HEMOLYMPH AMMONIA CONCENTRATION AND AMMONIA EXCRETION RATE OF CRANGON-CRANGON (L)

Physical manipulation (capture and handling) was found to have a signi ficant effect on the haemolymph ammonia concentration and ammonia excr etion rate of freshly-caught and laboratory-held Crangon crangon (L.) (Crustacca, Decapoda). In a Danish population of C. crangon a rapid in crease of 40% (P < 0.05) in circulating ammonia during the first 7.5 m in after handling was followed by a sustained (ca. 6 h) decrease. The haemolymph ammonia concentration 6.3 h after handling was 56% (P < 0.0 05) below the in situ value estimated for this population. Twenty-five hours after handling the circulating ammonia concentration had return ed (P = N.S.) to the in situ value. In a British population of C crang on a more rapid (ca. 6 h) return of circulating ammonia concentration to the estimated in situ value was a function of the maintenance of in ternal/external NH3 and NH4+ gradients during exposure to a gradually increasing seawater ammonia concentration. A 60% (P < 0.001) drop in t he ammonia excretion rate of freshly-caught Danish C. crangon over the first 5.5 h after handling is attributed to a decrease in the release of ammonia from the tissues. These observations indicate that physica l manipulation can affect crustacean nitrogen metabolism.