Quantitative estimation of proteolytic enzyme and ultrastructural study ofanterior part of intestine of Indian major carp (Catla catla) larvae during ontogenesis

Specific proteolytic enzyme activity and ultrastructure of the anterior par t of the intestine of Catla catla larvae were studied during ontogenesis. S pecific proteolytic activity of larvae cultured under three feeding schemes of live-food, refrigerated-plankton food and starvation showed that the en zyme activity increased along with age regardless of feeding conditions. Th ere was no significant difference in enzyme activity between larvae fed liv e-plankton and refrigerated-plankton during the initial 9 days, but it beca me significantly (P < 0.001) higher in the former than the latter from day- 10 onwards. Highest activity was observed in the 26-day larvae of live-food treatment (0.987 +/- 0.02 mg of tyrosine/mg of protein/h). In the starvati on treatment, activity was significantly lower throughout the culture perio d. Ultrastructure study of the digestive system also supported the results of quantitative estimation. Microvilli, microfilament bundles and secretory granules showed progressive changes along with age. Age-related changes in the diversity and quantity of digestive enzymes appear to represent evolut ionary adaptations to the different natural diets and nutritional requireme nts of distinct life-history stages.