Growth and ontogenetic change in activities of digestive enzymes in Fennero Penaeus indicus postlarvae

Abstract

The growth and enzyme response of Fennero Penaeus indicus postlarvae (PL) was assessed with natural and artificial diets for the first 2 weeks of PL development to PL14 (14 days after metamorphosis to PL1). At PL14, postlarvae reared under similar conditions were separated into two size groups based on slow growth (9.57 ± 0.46 mm) and fast growth (13.90 ± 0.28 mm), and reared for a further 63 days. Growth among postlarvae PL1 and the smaller size group at PL14 fed on artificial diet was significantly slower than that of PLs fed on Artemia nauplii or fresh mussel. In contrast, the larger size group at PL14 did not show a significant difference in growth when fed artificial diet or fresh mussel. Trypsin and amylase response was significantly related to postlarval total length (P < 0.001); thus, digestive enzyme response increased with size and stage of development, but did not change significantly with diet fed. The amylase–protease ratio increased from PL1 and amylase activity became higher than the activity of trypsin for 2–3 weeks after metamorphosis. It appears that during the early stages of development postlarvae are unable to digest artificial diets efficiently because of low digestive capacity. Hence, poorly digestible feed delayed development and increased size variability. For smaller PL14, poor performance on artificial diets is possibly linked to a genetically regulated constraint, but not to digestive capacity since enzyme levels were similar to those found in larger PL14. During postlarval stages digestive enzyme production seems to be developmentally cued so that for postlarvae it appears that more digestible high-energy diets are required to reduce size variability during the nursery phase.