Digestive response and rates
of growth in pre-leptocephalus larvae of the Japanese eel Anguilla
japonica reared on artificial diets
B.H.
Pedersen, B. Ueberschär, T. Kurokawa-2003
Aquaculture, 215(1-4): 321-338
Abstract:
As food protein digestion is instrumental for
promoting growth, the main protease in young marine fish larvae, trypsin,
was studied in pre-leptocephalus larvae of Anguilla japonica. Tryptic
enzyme activity was monitored until day 24 and rates of growth until day 36
after hatch in larval A. japonica derived from artificially matured
parent fish. Tryptic activity increased with larval age and developmental
stage until day 16, after which tryptic levels stabilized. In start-feeding
larvae, tryptic activities increased after ingestion of an artificial diet,
but elevated tryptic activities could also be found in larvae with guts void
of prey, possibly due to intestinal retention of trypsin secreted in
response to ingestion of a previous meal. Gut retention time for trypsin was
estimated to be at least 15 h. The gut evacuation time for the artificial
diet depended on the meal size and was in the range of 1–5.5 h. Rates of
larval growth in length were ca. 5% day-1 during the yolk-sac
stage, declining to ca. 1% day-1 in older larvae. Vision was
highly important for initiation of feeding. Results provide the first
quantitative information on aspects of protein digestion in eel larvae.
(Marine Biological Laboratory, University of
Copenhagen, Strandpromenaden 5, DK-3000, Helsingør, Denmark, Tel.:
+45-49213344; fax: +45-49261165; email: benedikte.pedersen@privat.dk)