367 Effect of vitamin C on the survival, moulting and whole body ascorbic acid content of Macrobrachium rosenbergii (de Man) juveniles GIJO ITTOOP* AND SUSHEELA JOSE College of Fisheries, Panangad, Kochi -682506, India * Present address : CMFRI, Cochin ABSTRACT An experiment was conducted to find out the influence of dietary vitamin C on the survival, moulting rate and tissue ascorbic acid content of Macrobrachium rosenbergii juveniles. Vitamin C was fed in a semi purified diet at eight levels @ 0, 45, 67.5, 90, 112.5, 135, 180 and 450 mg AAE (ascorbic acid equivalent)/kg to the experimental animals for 56 days. The results showed that below a level of 67.5 mg AAE/kg diet, the survival rate was very poor mainly due to incomplete moulting. Black lesions were observed at the tip of the appendages of dead animals. Above 90 mg AAE/kg diet, survival and moulting rates were satisfactory. The whole body ascorbic acid content reached a steady state only at 135 mg AAE/kg diet and hence the minimum amount of ascorbic acid recommended in the diet of M. rosenbergii is 135 mg AAE/ kg. Indian J. Fish., 53(4) : 367-372, Oct.-Dec., 2006 Introduction Vitamin C or ascorbic acid is one of the most important micronutrients studied because of the high mortality caused by its deficiency both in fin fish and shell fish (Halver, 1989). It is required for normal collagen synthesis and therefore its deficiency leads to mortality associated with incomplete moulting in crustaceans (Hunter et al., 1979; Lightner et al., 1979; Magarelli et al., 1979; He and Lawrence, 1993). It also plays an important role in disease resistance (Felix and Sivakumar, 2003). It is highly significant in the present day aquaculture scenario vested with problems of disease and associated mortality. Deshimaru and Kuroki (1976) who made the first step towards defining specific vitamin requirement of prawns found that in Marsupenaeus japonicus, survival was the most important parameter affected by ascorbic acid deficiency. Moreover, it is also reported that the optimum dietary concentration of vitamin C is equivalent to the amount that maintains a steady state tissue vitamin C concentration (Dabrowski, 1990). Since Macrobrachium rosenbergii is an important candidate species in aquaculture of both tropical and temperate climates, the present study was conducted with a view to determine the influence of dietary vitamin C on survival, moulting rate and whole body ascorbic acid content in juvenile prawns.