Ontogenetic Development of Digestive Tract and Enzymes Activity in Hatchery-reared Pink Ear Emperor, Lethrinus lentjan Larvae

Ontogenetic development of the digestive tract and associated organs of Lethrinus lentjan larvae were learned by observing changes in external morphology, histology, and enzymatic changes from hatchling to 40-day post-hatching (dph). Ontogenetic development of the L. lentjan digestive system can be divided into three major stages; the first stage from hatching of larvae to complete absorption of yolk-sac, which ends on 2 dph, the second stage from 3 to 15 dph i.e., from exogenous feeding to the formation of the gastric gland and third stage till completion of metamorphosis (35 dph). Pyloric caeca were developed after 20 dph, which was formed entirely by 27 dph. Enzymatic activities of amylase, lipase, trypsin and chymotrypsin were detected before the onset of exogenous feeding and pepsin was detected from 19 dph onwards in L. lentjan. So considering both histology of digestive tract and enzyme development, weaning of L. lentjan larvae to artificial diet can be practiced after 19-20 dph coinciding with the formation of pyloric caeca and production of pepsin enzyme for better digestibility and consequently better growth and survival. The present study can be expended as a reference guide to understand the digestive tract development and successful hatchery rearing of other economically important marine fishes.