Hemolymph ammonia and urea and nitrogenous excretions of Scylla serrata at different temperature and salinity levels

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 degrees C combined with 10, 25 and 40 parts per thousand 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 (mu g g(-1) h(-1)) increased with a decrease in salinity, whereas urea-N excretion increased with an increase in salinity. At 25 degrees C, ammonia-N excretion accounted for 82.0, 79.2 and 56.2 % of total nitrogen excreted by the crabs at 10, 25 and 40 parts per thousand S, whereas urea-N excretion accounted for 4.3, 9.1 and 30.1 % respectively. It is concluded that the S. serrata at 40 parts per thousand S shifts its excretory pattern from ammoniotelism to ureotelism.