VITAMIN-C REQUIREMENT OF THE JUVENILE FRESH-WATER PRAWN, MACROBRACHIUM-ROSENBERGII

A quantitative dietary requirement of vitamin C has been determined fo r the juvenile freshwater prawn, Macrobrachium rosenbergii, using two water-stable sources of ascorbic acid, ascorbyl-2-monophosphate, calci um salt (AMP) and ascorbyl-6-palmitate (AP). Vitamin C was either not included or added to a semipurified diet at levels of vitamin C activi ty ranging from 10 to 200 mg/kg. A control diet contained 5000 mg of c rystalline L-ascorbic acid/kg of diet. Mortality in vitamin-C-deficien t diets (50 mg/kg) was observed within 21 days after initiation of two independent feeding trials conducted for 79 and 90 days and was gener ally associated with the lack of successful extrication from the old e xoskeleton. Survival increased as the level of vitamin C activity incr eased from 0 to 100 mg/kg of diet. AMP and AP showed equimolar vitamin C activity. A quantitative requirement equivalent to 104 mg of vitami n C/kg of diet was estimated by a quadratic surface analysis, using su rvival as the measured response to the different dietary levels. This estimated requirement is one to two orders of magnitude lower than tho se determined for species of penaeid shrimp using dietary sources of a scorbic acid that are more water-soluble and less stable.