Study on population hybridization of two shell color strains of Manila clam Ruditapes philippinarum

The population hybridization was conducted by using clams of two shell color strains " ocean red" (R), " zebra" (Z) strains in October of 2007. The experiments was consisted of RR (R♀×R♂), ZZ (Z♀×Z♂), RZ(R♀×Z♂), ZR (Z♀×R♂) groups. The results showed that difference of shell length, weight and fecundity of parents were significant between two shell color strains (P < 0.05). There were no difference on egg-diameter, fertilized rate and size of D larvae among each experimental groups (P > 0.05).The hatching rates in hybrid groups were higher than in control groups (P < 0.05).At the planktonic stage, survival heterosis was obvious instead of growth heterosis for larvae tested. Survival heterosis were(10.30±1.92)%and(16.30±1.04)%, respectively for RZ and ZR, and growth heterosis for RZ, ZR were(1.63±0.81)%and(2.58±0.67)%.Growth rates for RZ, ZR were (8.64±0.32) and (8.67±0.31) μm · d^-1, respectively (P < 0.05).At indoor rearing stage, obvious growth and survival heterosis were found. The growth heterosis of RZ, ZR were(11.25±2.98)%and(20.31±2.10)%, the growth rates were (9.88±1.45) and (10.79±1.32) μm · d^-1, and the survival heterosis were(40.85±9.90)%and(57.08±11.98)%, respectively. There was no significant difference of survival heterosis between RR and ZZ (P < 0.05).