Effects of salinity on rates of protein synthesis and oxygen uptake in the post-larvae and juveniles of the tropical prawn Macrobrachium rosenbergii (de Man).

Protein synthesis is a major determinant of growth and yet little is known about the environmental factors that influence protein synthesis rates in farmed freshwater prawns. To this end, post-larvae and juveniles of Macrobrachium rosenbergii were exposed to various salinities (0, 14, 30 per thousand) to determine whole-animal rates of fractional protein synthesis (k(s)) and oxygen uptake. In the post-larvae that migrate upstream from brackish to freshwater areas, whole-animal k(s) was unaffected by salinity, but rates of oxygen uptake were significantly lower at 14 per thousand. In the freshwater juveniles, a different response was observed, as mean k(s) was significantly higher at 14 per thousand compared with 0 per thousand, but rates of oxygen uptake remained unchanged. Such differences are thought to be related to the energetic costs of osmoregulation and to the ability to maintain osmotic gradients in freshwater. In an additional experiment, acclimation temperature (20, 26, 30 degrees C) had a direct effect on k(s) in juveniles held at 0 per thousand. In all cases, changes in k(s) resulted from alterations in RNA activity at constant RNA capacity. In juveniles at least, whole-animal rates of protein synthesis were highest at 14 per thousand and 30 degrees C which corresponds to the optimal salinity and temperature recommended for the growth and culture of M. rosenbergii.