Ontogenetic variation in
digestive proteinase activity, RNA and DNA content of larval and postlarval
white shrimp Litopenaeus schmitti
D. Lemos, F.L. Garcia-Carreño, P. Hernández, A.
Navarrete del Toro-2002
Aquaculture, 214(1-4) :
363-380
Abstract:
Proteinase (endopeptidase), trypsin and chymotrypsin
activities, RNA, and DNA contents were examined throughout the ontogenetic
development of cultured Litopenaeus schmitti. Whole individuals from
larval and postlarval stages, and adult hepatopancreas were homogenized and
assayed for quantification of enzyme activity. Proteinase activity of
different life stages was characterized by substrate-SDS-PAGE. Specific
inhibitors for trypsin (TLCK) and serine proteinases (PMSF) were used to
identify activity zones of these enzymes in gels. Nucleic acids were also
quantified in larval and postlarval stages. Protein-specific activity of
total proteinases and trypsin presented higher values in nauplius IV (N IV),
protozoea I (PZ I), and PZ III, compared to the remaining stages, while
chymotrypsin activity peaked in N IV and PZ III. Enzyme activity was lower
in egg, early nauplius, mysis, and postlarval stages. Different proteinase
patterns were observed in SDS-PAGE during ontogenetic development. Active
bands of 15.5, 16.0, 19.9, 21.8, 24.0, 27.9, 30.3, 33.5, 35.5, 38.2, and
48.1 kDa were detected in the adult hepatopancreas. In the course of
development, proteolytic activity was detected in N IV, and intense bands of
17.3, 19.9, and 20.9 kDa were found up to mysis (M III). A band at 38.2 kDa
was present between N IV and M I, and between PL II and PL IV. Most bands
were serine proteinases, and only two bands in adult (15.5 and 15.9 kDa)
were inhibited by TLCK. Both RNA and DNA contents (µg mg-1 of
fresh weight) reduced with development from egg to PZ III, increasing
afterwards until PL IV. RNA/DNA ratios increased from egg, reaching a peak
in PZ I, and decreased in the following stages until a minimum was reached
in M II. A secondary peak was observed in PL III followed by reduction in PL
IV. The variation in enzyme activity indicates different strategies of
energy use throughout development. Higher enzyme activity combined with
increased RNA/DNA in protozoeal stages denotes intense food energy use and
accumulation into growth. The shift in energy strategy during the ontogeny
of L. schmitti is accompanied by variation in proteinase
characteristics as observed in other penaeid species.
(Instituto Oceanográfico, University of São Paulo,
C.P. 66149, São Paulo 05315-937, Brazil, e-mail: dellemos@usp.br)