Genetic parameter estimates for growth traits at early stage of Pacific abalone,Haliotis discus hannai Ino

Heritability and genetic and phenotypic correlations were estimated for juvenile growth traits of Pacific abalone Haliotis discus hannai Ino. The estimates were calculated from shell length and shell width measurements on progeny resulting from 12 half-sib families and 36 full-sib families obtained using artificial fertilization of mating three females to each male. The measurements were taken at 10, 20 and 30 d after fertilization. It was found that heritability estimates based on sire component ranged from 0.23 to 0.36 for shell length and 0.21 to 0.32 for shell width. Heritability estimates from dam component were larger than those from sire component at three ages, indicating presence of maternal effects, non-additive genetic effects and common environmental effects. Phenotypic correlations were significant at three ages （P 〈 0.05）, with values of 0.92, 0.93 and 0.92, respectively. Genetic correlations from the paternal half-sib correlation analysis were highly positive at three ages, with values of 0.50, 0.78 and 0.81, respectively. The results suggest that selective breeding is an effective approach to improving growth traits of Pacific abalone stocks.

Heterosis and combining ability:a diallel cross of three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino

We conducted a complete diallel cross among three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino to determine the heterosis and the combining ability of growth traits at the spat stage.The three populations were collected from Qingdao(Q) and Dalian(D) in China,and Miyagi(M) in Japan.We measured the shell length,shell width,and total weight.The magnitude of the general combining ability(GCA) variance was more pronounced than the specific combining ability(SCA) variance,which is evidenced by both the ratio of the genetic component in total variation and the GCA/SCA values.The component variances of GCA and SCA were significant for all three traits(P<0.05),indicating the importance of additive and non-additive genetic effects in determining the expression of these traits.The reciprocal maternal effects(RE) were also significant for these traits(P<0.05).Our results suggest that population D was the best general combiner in breeding programs to improve growth traits.The DM cross had the highest heterosis values for all three traits.

Acclimation-dependent expression of heat shock protein 70 in Pacific abalone (Haliotis discus hannai Ino) and its acute response to thermal exposure

Heat shock protein 70 （Hsp70） is one important member of heat shock protein （Hsp） family that is responsible for various stresses, especially thermal stress. Here we examined the response of Hsp70 gene to both chronic and acute thermal exposure in Pacific abalone （Haliotis discus hannai Ino）. For the chronic exposure, abalones were maintained at 8, 12, 20, and 30∩ for four months and their mRNA levels were measured. The highest mRNA level of Hsp70 gene relative to actin gene was detected in the 30~C-acclimated group, followed by the 8~C-acclimated group and then the 12~C- and 20~C-acclimated groups. After the long-term acclimation, gills from each of the above acclimation groups were dissected and exposed to different temperatures between 8~C and 38~C for 30 min. Hsp70 expression in gills acclimated to different temperatures responded differentially to the same temperature exposure. The incubation temperature that induced maximum Hsp70 mRNA expression was higher in the higher temperature acclimation groups than lower temperature groups. Pacific abalones could alter the expression pattern of Hsp70 gene according to environmental thermal conditions, through which they deal with the stress of thermal variations.

Experimental evaluation of heterobeltiosis and heterosis between two populations of Pacific abalone Haliotis discus hannai Ino

A2 × 2 factorial cross between two populations of Pacific abalone Haliotis discus hannai Ino, collected separately from Dalian （D） in China and Miyagi （M） in Japan, was conducted to compare performances in fertilization rate, hatching rate, metamorphosis rate and growth at days 20, 43, 160 and 330 between purebreds （DD and MM） and crossbreds （DM and MD） and investigate the magnitude of heterobeltiosis （better parent） and heterosis （mid-parent）. Heterobeltiosis and heterosis for all the traits analyzed were evidently different between crossbreds DM and MD. Heterobeltiosis in the crossbred DM varied among traits, with values of 2.5% for the fertilization rate, 2.2% for the hatching rate, - 1.9% for the metamorphosis rate and 7.4% for the growth at the day 330. The crossbred DM displayed positive heterotic values for fertilization rate （5.4%）, hatching rate （7.4%）, metamorphosis rate （7.6%） and growth （ 12.0% ） at the day 330. However, both heterobeltiosis and heterosis for all the traits in the crossbred MD were negative except those for the growth at days 20 and 43. The results indicate the importance of selecting superior hybrid varieties if the exploitation of hybrid vigor is considered in the Pacific abalone breeding program.

Growth of eight Pacific abalone families at three temperatures

Growth rates, measured as shell length and body weight daily growth, were studied in the eight families of Pacific abalone, Haliotis discus hannai Ino, reared at 12, 16 and 20 ℃for 40 d respectively. The results show that J1Rh family grew the best at 12 ℃, with growth rates of (32.88±4.66) μm/d and (5.24±1.84) mg/d. C1Jm family had the highest growth rates of (58.00±2.00) μm/d and (9.71±1.21) mg/d at 16 ℃. J1Jm family ranked the first at 20 ℃, with growth rates of (66.00±1.76) μm/d and (10.99±0.34) mg/d. RjRh family had the slowest growth rates at all three temperatures. Shell length growth rates were 18.25, 33.00 and 43.13 μm/d respec- tively, while body weight growth rates were 2.47, 2.56 and 4.75 mg/d respectively. Both temperature and family had significant effect on growth rates (P< 0.05). At 16 and 20 ℃, maternal effects on growth rates were not significant (P> 0.05), but paternal effects on growth rates were significant (P< 0.05). Results of this study indicate genetic difference among the families and importance of select- ing male breeders in the commercial hatchery.