Ontogenetic variation in digestive enzyme activities within embryos and newly-hatched larvae of the tropical spiny lobster, Panulirus ornatus

Abstract

While there is considerable interest in aquaculture of spiny lobsters (Palinuridae), limited knowledge of nutritional requirements during early life stages remains a major impediment to successful hatchery culture. To better determine endogenous nutrient utilisation during the early life stages of the tropical spiny lobster, Panulirus ornatus, we examined ontogenetic variation in digestive enzyme activities within developing embryos and newly-hatched phyllosoma in the absence of an exogenous food source. Specifically, α-amylase, non-specific esterase, and trypsin-like protease activities were quantified to indicate the relative importance of macronutrients (i.e., carbohydrate, lipid, and protein) and gauge the digestive potential of newly-hatched phyllosoma during transition from endogenous to exogenous nutrient sources. Ontogenetic variation in digestive enzyme activities indicated that lipid, protein, and carbohydrate were sequentially utilised by embryos. Early increase in non-specific esterase activity suggests that lipid is the most critical macronutrient for early embryonic development, with protein and carbohydrate becoming increasingly utilised shortly before and after hatching. The observed peak in trypsin-like protease activity during the first day post-hatch presumably allows phyllosoma to make best use of dietary items that are high in protein at first-feeding. In the absence of an exogenous food source after hatching, changes in digestive enzyme activities suggest that a metabolic shift from protein to lipid occurred, coinciding with the timing of the ‘point-of-no-return’ for Stage I phyllosoma of P. ornatus. Our results highlight the importance of providing an exogenous protein-rich food source to phyllosoma soon after hatch and provide a foundation for further study into broodstock nutrition and egg quality of this species.