Effects of Various Sodium and Potassium Concentrations Mediums on Na/K-Atpase Activity and Condition Indices at Different Larval Stages of Macrobrachium rosenbergii

Macrobrachium rosenbergii lifecycle is unique so that the adults thrive in freshwater and larval development requires brackish water environments near to estuaries as close as possible to larval body isosmotic for minimum Na/K-ATPase activity and maximum ATP storage. Osmoregulation system at early larval stages is not formed and larval osmoregulation is mainly attributed to Na/K-ATPase activity. The present study aimed to evaluate effects of various sodium and potassium concentrations on Na/K-ATPase activity, larval condition index (LCI) and survival rate of M. rosenbergii at 1st, 4th, 7th and 11th larval stages. Triplicate treatments of Sodium (2000, 3000, 4000 and 5000 ppm) and potassium (100, 150, 200 and 250 ppm) were prepared separately in tanks (100‑L) and initial larvae density was fixed 200 larvae L-1. The treatments were set up at 12 ppt salinity based on New artificial brackish water composition. To adjust desired concentrations of sodium and potassium for the treatments, their soluble salts, including NaCl and KCl, were used. The results indicated that evaluation of the freshwater prawn larval quality according to Na/K-ATPase activity is a better index than LCI and survival rate. The results also showed that isotonic condition and minimum Na/K-ATPase activity at 1st and 4th larval stages and 7th and 11th stages occurred respectively in 4000 and 3000 ppm sodium treatments but this index for potassium treatments was 150 ppm for the all larval stages.