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Ontogenic development of enzymatic activity and digestive system in Jullien's golden carp (Probarbus jullieni Sauvage, 1880)

Limtipsuntorn, Ubonrat, Rungsin, Wikrom, Thongprajukaew, Karun, Boonyung, Wiwihthanon, Rangsin, Wannapa
Aquaculture research 2018 v.49 no.10 pp. 3362-3373
Carassius auratus, Moina, Probarbus jullieni, amylases, artificial diets, artificial insemination, body weight, chymotrypsin, endo-1,4-beta-glucanase, enzyme activity, fish larvae, hatching, histology, intestines, lipids, protein degradation, trypsin, weaning
Ontogenic development of the main enzymes and histological structure of digestive organs were studied in Jullien's golden carp (Probarbus jullieni) from hatching until 50 days after hatching (DAH). The larval fish were produced by artificial insemination and fed only Moina sp. till end of experiment. Body weight (mg) and total length (cm) of Jullien's golden carp increased exponentially and linearly. The results indicate the fish weight grew fast with increasing rate, while length increased at a constant rate over the studied period. Up‐regulation of acid protease was observed in newly hatched larvae and the specific activity gradually decreased with time. Trypsin specific activity was relatively stable within the first 35 DAH, while fluctuations in chymotrypsin were observed. Among these three proteolytic enzymes, acid proteases exihibited relatively high specific activity in newly hatched larvae, suggesting a role in yolk protein degradation. Alkaline proteases became more prominent with age and correlated with an abrupt decrease in acid proteases. Increased lipase‐specific activity appeared within 3 DAH and then gradually decreased with time, indicating the capacity to digest yolk lipid reserve. Amylase and cellulase‐specific activities changed in a similar manner, and the sensitivity to time was higher in amylase than in cellulase. The digestive organs and accessory organs developed around 3–5 DAH. However, intestinal histology was almost fully developed around 18 DAH. These findings should be useful for deciding the preferred timing for weaning, as well as on developing artificial diets referenced to the physiological changes of digestive enzymes.