Ontogeny and induction of digestive enzymes in Scylla serrata larvae fed live or artificial feeds or their combination

Generally, the patterns of digestive enzyme activities during ontogeny and the digestivecapacities of most crab larvae are less understood. In the present study, ontogenetic patterns of enzymeactivities of amylase, trypsin and leucine aminopeptidase (LAP) were investigated for the first time indeveloping Scylla serrata larvae. Moreover, the influence of diet types (live feed, artificial feed orcombination of both feeds) on larval digestive enzyme activities was also examined. Results showed thatamylase activity were low at early larval stages zoea 1 (Z1) to zoea 3 (Z3), exhibited enzyme activitypeaks at stages zoea 4 (Z4) and zoea 5 (Z5) and declined gradually at megalopa to crab instar 1(C1)stage. Trypsin showed an elevated activity at Z2, remained low at later stages but enzyme activity roseagain from megalopa until reaching the highest activity at the C1 stage. In contrast, LAP enzymeactivities increased gradually from Z3, reaching a maximum at the C1 stage. Factorial ANOVA showedthat enzyme activities were influenced by the developmental stage, by the type of diet, and by theinteraction of these factors. Also, the use of Discriminant Analysis (DA) allowed us to show that therewas a significant effect of the diet as well as development stage on digestive enzyme activities.Furthermore, DA allowed us to rank the parameters that weighted mostly in the model:trypsin>LAP>amylase in discriminating between development stages while only LAP was the predictorvariable for discriminating between diets.