INFLUENCE OF LIVE AND ARTIFICIAL DIETS ON TISSUE COMPOSITION AND TRYPSIN ACTIVITY IN PENAEUS-JAPONICUS LARVAE

Penaeus japonicus larvae were reared using live food, an artificial di et or an artificial diet plus C. gracilis. Larvae from all treatments were equivalent in weight and length at the third protozoeal stage, bu t mysis and postlarvae from both the live food and the artificial diet plus C gracilis treatments were significantly larger and reached meta morphosis earlier than those fed the artificial diet alone. There were significant increases in percentage nitrogen and carbon contents duri ng development in larvae fed the live food or the artificial diet plus C gracilis, but not of larvae fed the artificial diet alone. High gro wth and nitrogen and carbon retention in mysis larvae fed live food wa s accompanied by a drop in trypsin activity. Despite a strong trypsin response to the artificial diet, mysis larvae appear unable to assimil ate sufficient dietary protein to support growth equivalent to that ob served in larvae fed live food. Supplementing the artificial diet with a low density of C. gracilis produced postlarvae of the same size and tissue composition as those reared using live food. It is suggested t hat the algal co-feed contributes either extra digestible nutrients or some specific growth-enhancing factor(s).