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‰) 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‰. In the freshwater juveniles, a different response was observed, as mean k_s was significantly higher at 14‰ compared with 0‰, 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 °C) had a direct effect on k_s in juveniles held at 0‰. 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‰ and 30 °C which corresponds to the optimal salinity and temperature recommended for the growth and culture of M. rosenbergii.