| Hybrids, Chlamys farreri♀×Patinopecten yessoensis♂were studied on fertilization, genetic analysis and growth in D-shaped stages with the cytobiological method and experimental ecology. We applied hydrostatic pressure to induce allotriploidy (Chlamys farreri♀×Patinopecten yessoensis♂) and allotetraploidy (Chlamys farreri♀×Argopecten irradiants♂). The suitable inducing factors, genetic analysis, ploidy investigation and growth were discussed in this study. All information would be the foundation for scallop Chlamys farreri breeding.Zhikong scallop is one of the most important cultured mollusks in the north of China, which had brought great income. Recently, its output is reducing because of its weak resistance to environment. So, we try to induce allopolyploidy to improve its quality. Results showed that sperms from Patinopecten yessoensis penetrated into eggs of C. farreri and played a part in zygotes development. Karyotypes and GISH approved that larvae we got were hybrids. However, hybrid larvae's fertilized percentage, hatchery rates and survivorship were lower than those of control group (C. farreri♀×C. farreri♂). Based on results above, zygotes, crossing between female C. farreri and male Patinopecten yessoensis were treated with hydrostatic pressure to induce allotriploidy through inhibiting polar body I or II. Hydrostatic pressure does no harm to environment and human beings, which was the crucial advantage against chemical methods. Inhibiting polar body II, we got about 50% triploidy and 29% aneuploidy at the same time. It is better than those through inhibiting polar body I, from which we just got about 43% triploidy. In later D-shaped stage, triploid percentage reduced from 50% to about 30%. Some larvae did not settle or metamorphose with unknown reason. So the research was broken off. It is hard to evaluate whether allotriploidy would be grow fast as we expected. Tetraploidy mating diploidy is the best method to gain triploids, which would be 100%...
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