Digestive Enzymes of the Developing Sepia pharaonis Ehrenberg 1831 Paralarvae

Abstract

In order to understand the digestive physiology of Sepia pharaonis Ehrenberg 1831 (Sepiidae) paralarvae, and to formulate appropriate feeding strategies, the activity patterns of major digestive enzymes in relation to larval development were investigated. Trypsin, leucine aminopeptidase, alkaline phosphatase, alpha-amylase, and lipase were analyzed for 25 days from hatching. Results revealed that all digestive enzymes were present even prior to exogenous feeding, and each enzyme exhibited a distinct activity pattern. Leucine aminopeptidase, an enzyme involved in intracellular digestion, was found to be dominant and highly active at early developmental stages and declined with larval maturation. Lipase activity, involved in lipid metabolism, increased in the early stages of development but declined 10 days after hatching (DAH). Secreted enzymes (trypsin and amylase) and alkaline phosphatase (an indicator of larval gut maturity) exhibited low activity prior to 10 DAH and 13 DAH, respectively. However, these enzymes became highly active in the late developmental stages. These findings suggest the gradual gut maturation of S. pharaonis based on intracellular and secreted enzyme activities. The findings also indicate that paralarvae after hatching are well-equipped with digestive enzymes necessary to digest complex food items, and that the larval gut matures 13 to 20 DAH.