Ontogenetic variation in digestive proteinase activity of larvae and postlarvae of the pink shrimp Farfantepenaeus paulensis (Crustacea: Decapoda: Penaeidae)

Proteinase (endopeptidase), trypsin-like and chymotrypsin-like activities were examined throughout the ontogenetic development of cultured Farfantepenaeus paulensis. Whole individuals from different larval and postlarval stages, and the hepatopancreas of adults were homogenized and assayed to quantify the enzyme activities of specific substrates. Proteinase activity was identified by substrate-SDS-polyacrylamide gel electrophoresis. Specific inhibitors for trypsin (TLCK), chymotrypsin (TPCK) and serine proteinases (PMSF) were used to identify activity zones of these enzymes in gels. Protein-specific activity of total proteinases, trypsin and chymotrypsin was negligible at the egg stage and at Nauplius III, increasing in the first protozoeal substage (PZ I), and reaching a peak at PZ III; it decreased again in the subsequent postlarval substages. Different patterns of proteinase activity were observed in SDS-PAGE zymograms during ontogenetic development. Active bands of 14.6, 16.4, 17.5, 19.5, 22.5, 23.9, 25.8, 28.9, 32.0, 34.4, 37.7, and 42.2 kdaltons were detected in the adult hepatopancreas. Proteolytic activity was detected on gels in PZ I, and intense activity zones of 16.4, 17.5 and 19.5 kdaltons were found up to Mysis I (M I). Intense bands of 39.1 and 53.5 kdaltons were observed only at PZ III and M I. Band-activity intensity decreased after metamorphosis to the postlarval stage (PL). The chymotrypsin inhibitor TPCK had no effect on the proteinase bands. Active zones in gel inhibited with both TLCK and PMSF were considered to represent trypsin. The inhibitory effect of PMSF alone on proteinase extracts indicated chymotrypsin activity. TLCK and PMSF inhibition also varied during ontogenetic development. The inhibition of bands recorded between 14.6 and 21.7 kdaltons suggested the presence of low molecular weight trypsin in F. paulensis. The 39.1 kdaltons band observed at PZ III and M I were trypsin-like. On the other hand, bands of 28.9, 32 and 37.7 kdaltons from the adult hepatopancreas seem to represent a chymotrypsin. We conclude that the recorded variation in enzyme activity may be associated with morphological and behavioral changes during penaeid ontogenetic development. The higher enzyme activity at PZ II, PZ III and M I may reflect the increased energy turnover associated with intense swimming behavior and food ingestion. Received: 24 September 1998 / Accepted: 20 August 1999