Influence of Food Density on Digestive Enzyme Activities in Newly Hatched Larvae of the Spiny Lobster, Panulirus ornatus

Abstract

There is considerable interest in developing hatchery techniques for the tropical spiny lobster, Panulirus ornatus. Although some progress has been made toward identifying effective foods and feeding protocols for this species, the density at which food is first provided to larvae varies greatly in practice. This study examined relationships between food density and the activities of major digestive enzymes in P. ornatus to evaluate larval feeding protocols from a nutrient utilization perspective. Specifically, activities of α-amylase, nonspecific esterase, and trypsin-like protease were quantified to determine the response of newly hatched larvae of P. ornatus to provision of Artemia nauplii at three different densities. Results showed that food density significantly (P < 0.01) influenced α-amylase and nonspecific esterase activities during the first 24 h of feeding, but had minimal effect (P ≥ 0.09) on trypsin-like protease activities. Based on enzyme activities, there is no advantage to increasing food densities above 2.5 Artemia mL–1, but when food density decreased to 0.5 Artemia mL–1, the availability of dietary nutrients became limiting. An optimal density at which to provide Artemia nauplii to newly hatched larvae of P. ornatus is likely between 0.5 and 2.5 Artemia mL–1. The comparative analyses of enzyme activities presented in this study represents an innovative approach to identify potentially excessive or insufficient food densities quickly (within 24 h) for larval crustaceans.