Hemocyanin oxygen affinity, and the fractionation of oxyhemocyanin and deoxyhemocyanin for Penaeus monodon exposed to elevated nitrite

Hemocyanin oxygen affinity and the fractionation of oxyhemocyanin and deoxyhemocyanin in the hemolymph of Penaeus monodon were studied for individual shrimps exposed to 0.001 (control), 0.07, 0.36, 0.72 and 1.44 mmol l(-1) nitrite for 3 h up to 48 h in a salinity of 30 ppt at 25 degrees C. The hemolymph P-50 increased (indicating reduced affinity) and the hemolymph pO(2) increased directly with ambient nitrite and exposure time. Hemolymph pH. oxyhemocyanin and hemolymph protein were inversely related to ambient nitrite and exposure time. P. monodon, following 6 h exposure to ambient nitrite at 0.36 mmol l(-1), decreased significantly the fraction of oxyhemocyanin and increased that of deoxyhemocyanin. The increase of P,, and the increased fraction of deoxyhemocyanin suggests that hemocyanin) oxygen binding decreases with a concomitant decrease of hemolymph pH, when P. illoimonodon subjected to nitrite. (C) 1999 Elsevier Science B.V. All rights reserved.