Changes in Digestive Enzyme Activities of Larval and Early Crab Stages of Red Frog Crab Ranina ranina with Growth

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Developmental changes in digestive enzyme activities from zoeal to early crab stages in red frog crab (Ranina ranina) were investigated in the laboratory. Four thousands larvae were kept in 0.5 m3 tank at the temperature in ambient conditions (26.3±1.6°C). They were fed on Artemia nauplii from the first to fourth zoeal stages, thereafter frozen Japanese littlenecks, mysids, krills, and copepods were also given till early crab stage according to the developmental stages. The activities of trypsin-like enzyme and amylase were measured from one to 54 days after hatching (DAH). Both enzymes were clearly detected from the first zoeal stage (0 DAH), and they were elevated with growth, especially from the fifth zoeal stage (16 DAH). A marked increase of body weight was also observed from 16 DAH, and it was well synchronized with increases of digestive enzyme activities. Differentiation of functional midgut gland was clearly observed at 16 DAH suggesting that fundamental structure of the digestive systems were differentiated at this stage. The increase of trypsin-like enzyme and amylase activities coincided well with the differentiation and the development of midgut gland based on histological observation.
日本水産増殖学会の論文