ABSTRACT: Hemolymph ammonia and urea levels and nitrogenous excretions of Scylla serrata (Forskal) (202 ± 18 g) were measured when the crabs were exposed to 9 different temperature and salinity regimes (15, 25, 35°C combined with 10, 25 and 40o/oo S). Hemolymph ammonia increased with a decrease in salinity, whereas hemolymph urea increased with an increase in salinity. Nitrogenous excretion increased with temperature. Excretion of ammonia-N, organic-N, nitrite-N, and nitrate-N and total nitrogen excretion (µg g^-1 h^-1) increased with a decrease in salinity, whereas urea-N excretion increased with an increase in salinity. At 25°C, ammonia-N excretion accounted for 82.0, 79.2 and 56.2% of total nitrogen excreted by the crabs at 10, 25 and 40o/oo S, whereas urea-N excretion accounted for 4.3, 9.1 and 30.1% respectively. It is concluded that the S. serrata at 40o/oo S shifts its excretory pattern from ammoniotelism to ureotelism.

KEY WORDS: Scylla serrata · Temperature · Salinity · Hemolymph · Ammonia · Urea · Nitrogenous excretion · Metabolism

Published in MEPS Vol. 139 (1996) on August 29
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996