Studies On Parthenogenesis In Four Marine Bivalves

Parthenogenesis includes gynogenesis and androgenesis. Gynogenesis refers to the development of eggs fertilized by genetically inactivated sperm, and androgenesis is defined as all-paternal inheritance. Viable gynogenetic diploids can be generated by suppressing polar body or inhibiting the first cleavage to double paternally derived chromosomes, after fertilization of genetically inactivated sperm with normal eggs. Similarly androgenetic diploids can be generated by inhibiting the first cleavage to double paternally derived chromosomes, after fertilization of genetically inactivated eggs with normal sperm. Therefore germ plasm in gynogenesis or androgenesis comes from female or male without the other's join. Compared with classical genetic methods, parthenogenesis is a technique that could facilitate the production of homozygous isogenic lines, mono-sexual broods or clones, examination of sex determination, and protection of endangered species. It will provide a new way for genetic improvement of marine mollusks.In this study, optimum inductive parameters in the four marine mollusks, Atrina pectinata, Scapharca broughtonii, Chlamys farreri and Patinopecten yessoensis were tested and cytological processes in induction were observed. And gynogenetic diploids of Chlamys farreri were induced. The main results of this study are as followings:1. Karyotype and chromosome numbers of Atrina pectinata were studied. The karyotype calculated from chromosome lengths and arms ratios of cells was shown with: 2n=32, 8m+5sm+2st+1t, NF=29. The results provided basic data for heredity, taxology and breeding.2. Effects of ultraviolet irradiation on genetic inactivation of sperm and eggs were examined in Atrina pectinata, Scapharca broughtonii and Patinopecten yessoensis. UV irradiation of sperm for 40s and 45s respectively at a UV (254nm) intensity of 2561μW/(cm~2·s) were optimum doses to achieve haploid gynogenesis of Atrina pectinata and Scapharca broughtonii. And UV irradiation of eggs for 50s and 60s respectively at a UV (254nm) intensity of 1698μW/(cm~2·s) were optimum doses to achieve haploid androgenesis of Patinopecten yessoensis and Scapharca broughtonii. All the results were on the basis of observations on the fertilization and development rates and chromosome constitutions. The...