EFFECT OF DIETARY L-ASCORBYL-2-PHOSPHATE MAGNESIUM ON GONADAL MATURATION OF PENAEUS-JAPONICUS

P. japonicus (mean weight: female, 22.69 +/- 1.36 g; male, 20.51 +/- 1 .50 g) were fed semi-purified diets containing either 0, 500, 1000, or 1500 mg L-ascorbyl-2-phosphate magnesium (APM) as an ascorbic acid (A sA) source per kg dry diet for 170 days to investigate their effects o n growth, survival, and gonadosomatic index (GSI). Female prawns were unilaterally eyestalk-ablated on the 126th day of the experiment. The female prawns fed with an APM deficient diet had reduced resistance to changes which incurred through eyestalk ablation. Before eyestalk abl ation, the survival of females fed with an APM deficient diet was 100% ; however, after ablation, high mortalities were observed. The GSI of ablated females receiving 500 or 1000 mg APM/kg diet were significantl y higher (P<0.05) than those fed with 1500 mg. A level of 500 mg APM/k g diet was sufficient to promote good growth and survival in male praw ns. The GSI of males fed with an APM-deficient diet was not significan tly different from those fed with 500 or 1000 mg APM/kg diets. Prawn t issue AsA concentrations increased linearly with dietary levels of APM . AsA concentrations of female ovaries were higher than those of the m ale gonad.