| The noble scallop Chlamys nobilis Reeve has already become one of most important culturedshellfishes in Guangdong, Guangxi and Fujian provinces since late 1980s. With the developmentof breeding industry, however, problems like the germplasm degradation, value declining, and soon are becoming the bottleneck for the sustainable development of aquaculture industry. Newvariety with high-yield and high-value is urgently needed to promote the healthy development ofthe industry. For this, various bred stocks and families with orange, brown, and orange-purpleshell color were established by mass spawning and single mating on basis of a culture stock fromNan'ao, Guangdong Province. Meanwhile, genetics of the quantitative traits and shell color forthese breeding stocks and families were studied. Moreover, a new strain named"Nan'ao No.1"was bred. The main results are as follows.1 The quantitative traits including shell length, shell height, shell width, total weight, andadductor weight were compared by ANOVA and the genetic differences were analyzed by SSRamong scallops from the three shell colors of the culture stock.(1) Significant differences in the quantitative traits existed among the three shell colors, andthe individuals with orange were superior to those with the orange-purple or brown shell color.(2) Among the three shell colors, the observed heterozygosities were similar between0.56-0.57, and the Shannon's Indexs were all above 1.4, showing high polymorphism. Eventhough the variance among the shell colors was only 4.02%, there were still some geneticdifferentiations between the orange shell color and the others. Because The Fst between orange'sand brown's was 0.0588 and 0.0498 between orange's and orange-purple's, but it was 0.0220between brown's and orange-purple's. These results might due to the inheritance and theimbalance of ratio among the shell colors.2 Three bred stocks and lots of families with different shell colors were established, and thegrowth and survival among the stocks or families were compared at different stages.(1) The difference in larval survival was significant among the three stocks (P<0.05), but nosignificantly difference among families was tested during larvae except at days 10 (P<0.05).(2) During the larvae stage, the brown stock had significantly biggest shell length (SL) and shell height (SH) (P<0.05), and the orange stock had the smallest SL and SH at the same day(P<0.05); The orange families had significantly biggest SL and SH (P<0.05) at the 4 and 7 day(P<0.05), and the orange-purple families had the significantly smallest SL and SH (P<0.05).(3) The orange-purple bred stock and families both grew fastest during juvenile stage,whereas the orange bred stock and families both grew fastest during growup stage.3 The heritability of the quantitative traits in the early stage was estimated using thecorrelation method of full-sib and half-sib. The heritability ranged from 0.569 to 1.676 in SL andfrom 0.526 to 1.735 in SH. The heritability, which was 0.117 for hatching rate, was 0.260 and0.414 for larval survival rate at day 7 and day 10, respectively.4 Correlation and direct effects at the different levels of the culture stock, F1 bred stock, and F1families with orange shell color were studied by the path analysis. According to the results, shellheight should be the first selected trait in order to improve total weight if selection will be carriedout on the base of the culture stock or the F1 families, but shell length should be the first selectedtrait on the base of the F1 bred stock.5 The inheritance of shell color was preliminary studied by analyzing the data from differentshell color families. The shell color can be stably inherited. A simple dominant and recessivemodel can explain the genetic relationships among orange, purple, brown and orange-purpleshell colors. The orange was dominant to others and the brown was recessive to others, and adominant-epistasis effect from strong to weak was in order of orange, orange-purple, purple, andbrown.A effective method was established to induce spawning at all-weather conditions after severalexperiments, which can be applied indoors, outdoors, during the day and night, on sunny day orcloudy day. Within 30 mins, 95% female breeders were induced to spawn eggs and 100% malebreeders were induced to release sperms.Based on the theoretical and practical results mentioned above, after two continuousgenerations of families established, a new strain with high value and special features named"Nan'ao No.1"was bred. This new strain not only has orange shell color, orange mantle, andorange adductor, but also contains rich natural carotenoids in mantle and adductor.
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