In the present study, intraspecific crossing experiments between Chinese (H) and Thai populations (T) of Babylonia areolata were conducted by using a complete diallel design (H, T, TH, and HT). A total of 45 pedigreed families were obtained and cultured under the same environmental conditions. Positive heterosis was observed for many developmental parameters and shell sizes for most stages from juvenile to adult. Hatching and metamorphosis occurred significantly earlier in the hybrid (HT) than in the parent groups and a crossed group (TH). Rate of metamorphosis was also higher in HT than in the other three groups. Heterosis in shell length and body weight of the crossed group (HT) from the nursery and grow-out stage to harvest time was high and significantly different from the H, T, and TH groups. For mortality rate from juvenile to adult, total and average heterosis of the crossed group (TH) was positive and significantly different from H, T, and HT. The results of the present study show that intraspecies crosses can be a potentially useful way to increase the economic traits for B. areolata and thus provide a promising method for genetic improvement of the species as a new aquaculture stock in southern China.
Twelve paternal half-sib families (or 36 full-sib families) of the pearl oyster, Pinctada fucata martensii (Dunker), were produced according to the requirements of hierarchical genetic mating design. A total of 4320 individuals, aged 15 months, were measured for seven growth-related traits. Predicated upon the additive-dominance genetic analysis model, varying genetic variance components and then heritabilities of the growth-related traits of interest were estimated using analysis of variance. Results showed that seven growth-related traits had larger additive genetic variances (Po0.05); the dominance genetic variance of shell weight (SW) was smaller (P40.05), the dominance genetic variances of other six traits were all larger (Po0.05). Narrow-and broad-sense heritabilities for the seven traits were, respectively, 0.64 AE 0.10 and 0.78 AE 0.12 for shell length, 0.49 AE 0.06 and 0.63 AE 0.09 for shell height, 0.38 AE 0.14 and 0.54 AE 0.16 for shell breadth, 0.41 AE 0.17 and 0.56 AE 0.11 for hinge length, 0.53 AE 0.11 and 0.68 AE 0.08 for body weight, 0.35 AE 0.07 and 0.55 AE 0.08 for tissue weight and 0.67 AE 0.10 and 0.75 AE 0.16 for SW. All heritability estimates were statistically signi¢cant (Po0.05). According to these results, the mass selection procedure is suggested for the breeding of P. martensii.Estimating the heritability for growth-related traits in the pearl oyster H Wang et al.
In this study, the joint effects of two important environmental factors, temperature and salinity, on the per cent fertilization (FR) and per cent hatching (HR) of noble scallop, Chlamys nobilis, was evaluated using the central composite design and the response surface methodology. The results showed that the linear effects of temperature on FR and HR were significant (P < 0.01), and the linear effects of salinity were non-significant (P > 0.05); the interactions between temperature and salinity were not significant (P > 0.05); the quadratic effects of temperature and salinity on the two responses were significant (P < 0.01); temperature was more important in influencing the reproductive success. The model equations of FR and HR towards temperature and salinity were established, with R 2 more than 98%, indicating that the models had excellent ability for goodness of fit and projection. Through simultaneously optimizing the two models derived, we found out that the optimum factor combination was 25.7°C/ 29 ppt and the greatest reproductive success was 89.93% for FR and 72.42% for HR. The desirability value of 97.30% showed the reliability of these optima. Our results provide some valuable guidelines for refining the reproductive efficiency of C. nobilis.
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