Hemolymph oxyhemocyanin, protein, osmolality and electrolyte levels of Macrobrachium rosenbergii in relation to size and molt stage

Abstract

The giant river prawn, Macrobrachium rosenbergii (De Man), was examined for hemolymph oxyhemocyanin, protein, osmotic and ion concentrations in relation to sex, size and molt stage. No significant differences in hemolymph variables were observed between males and females with body weight in the range of 17–48 g. However, male prawns larger than 50 g had significantly lower levels of oxyhemocyanin, and a lower ratio of oxyhemocyanin to protein, Ca 2+ and Mg 2+. With regard to the molt cycle, hemolymph protein and oxyhemocyanin was highest (170.24 mg/ml and 2.01 mmol/l) at stage D 1, and lowest (110.18 mg/ml and 1.39 mmol/l) at stage A, respectively. Decreases in hemolymph protein, oxyhemocyanin, osmolality, Cl −, Na +, K +, Mg 2+, and Ca 2+ levels with size indicated that the prawns mature in the culture ponds. The fact that the hemolymph protein, osmolality, Cl −, Na + and K + levels were lower during the postmolt, and were higher during intermolt and early premolt, are considered to be associated with water uptake at molt.