THREE WAY CROSSES BETWEEN PURPLE AND WHITE-ORANGE INNER-SHELL COLOR STRAINS OF MANILA CLAM RUDITAPES PHILIPPINARUM
菲律宾蛤仔(Ruditapes philippinarum)紫壳内面和白黄壳内面品系的三元杂交

In order to improve the phenotypic character of Manila clam Ruditapes philippinarum, three way crosses were conducted between the generation F2 of purple (metamorphic heterosis) and white-orange (growth and survival heterosis) inner-shell color of R. philippinarum in June 2010. The growth, heterosis of reciprocal crosses (PWO, WOP) was investigated in the study. The results showed that: (1) As to growth, WOP (generation of the three way crosses) was the fastest experimental group during the planktonic period, and two crosses showed their heterosis in different degrees (HgPWO = 4.90±4.17 and HgWOP = 2.12±1.77) . It was mainly affected by the interaction between egg origin and mating strategy, and the next one is egg origin effect during the planktonic stage. During the juvenile stage, WOP was still the fastest one in growth, remarkably different with other groups (P<0.05) and showed obvious heterosis (HgWOP = 14.87±4.04). (2) As to survival rate, PP (self-fertilized group) was the lowest, and PWO (generation of the three way crosses) showed survival heterosis (HsPWO = 7.26±6.93) during the planktonic period. It was mainly affected by egg origin in planktonic survival. During the juvenile stage, WOP have a higher survival ability, and showed a little heterosis (HsWOP = 2.09±3.42). (3) As to metamorphosis, PP showed the lowest metamorphic ratio, it was remarkably different with other groups (P<0.05). The other three groups made no remarkable difference each other (P>0.05) , and the heterosis of PWO was 9.80.