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

The population hybridization was conducted by using clams Ruditapes plippinarum 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♂) and ZR (Z♀R♂) groups. 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-diameters, fertilization rates and sizes 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 (10.301.92)% and (16.301.04)%, respectively for RZ and ZR, and growth heterosis for RZ, ZR were (1.630.81)% and (2.580.67)%. Growth rates for RZ, ZR were (8.640.32) and (8.670.31) md-1, respectively (P＜0.05). At indoor rearing stage, obvious growth and survival heterosis were found. The growth heterosis of RZ, ZR were (11.252.98)% and (20.312.10)%, the growth rates were (9.881.45) and (10.791.32) md-1, and the survival heterosis were (40.859.90)% and (57.0811.98)%, respectively. There was no significant difference of survival heterosis between RR, and ZZ (P0.05).