No abstract

In this study, heritability was estimated for growth-related traits of giant freshwater prawn (Macrobrachium rosenbergii) before and after morphological sexual differentiation. Estimation was made on data from16 fullsib and eight half-sib families. The variance estimation was performed using a univariate mixed linear animal model and variance components were analysed following an animal model using restricted maximum likelihood procedure using average information algorithm. Heritability estimates (h 2 ) varied considerably with ages. At 2 months old, h 2 for carapace length (CL; 0.35 AE 0.15) and body weight (BW; 0.26 AE 0.13) were higher than those estimated at 5 months old, based on mixed sex data. However, when data were sorted by sex, h 2 calculated from data of females were higher than those of males for CL (0.26 AE 0.16 vs. 0.10 AE 0.06), BW (0.28 AE 0.17 vs. 0.12 AE 0.08), body length (0.40 AE 0.17 vs. 0.11 AE 0.07), total length (0.47 AE 0.18 vs. 0.11 AE 0.07) and claw length (0.29 AE 0.16 vs. 0.03 AE 0.04). The same trend was observed for traits at 6 months old in both bulk and individual rearing.

No abstract

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.

No abstract