Nitrogenous excretion in Macrobrachium rosenbergii at different pH levels

Abstract

Macrabrachium rosenbergii (31.1 +/- 1.9 g) were maintained individually in freshwater with pH levels of 4.15, 5.55, 7.10, 8.61 and 10.15 for 7 days, and then nitrogenous excretions from each animal for one day were measured. Ammonia-N excretion (mu g g(-1) h(-1)) and total nitrogen excretion (mu g g(-1) h(-1)) decreased with increased pH level, whereas urea-N excretion (mu g g(-1) h(-1)), nitrite-N excretion (mu g g(-1) h(-1)) and nitrate-N excretion (mu g g(-1) h(-1)) increased with increased pH level. Excretion of ammonia-N accounted for 78.90%, 73.63%, 68.66%, 55.06% and 45.45%, whereas excretion of organic-N accounted for 10.73%, 11.56%, 10.45%, 16.25% and 18.97% of total nitrogen excreted by the prawns at pH level of 4.15, 5.55, 7.10, 8.61 and 10.15, respectively. At high pH levels, excretions of urea-N, nitrite-N and nitrate-N may be related to the detoxification of ammonia.