泥鳅雄核发育纯合二倍体的产生

THE BIRTH OF THE ANDROGENETIC HOMOZYGOUS DIPLOID LOACH (Misgurnus anguillicaudatus)

以机械方法挑去泥鳅(Misgurnus anguillicaudatus)×大鳞副泥鳅(Paramisgurnus dabryanus)(♀)属间杂交受精卵的雌核,得到泥鳅雄核发育单倍体胚胎。将这种单倍体胚胎的囊胚细胞核移植到大鳞副泥鳅去核卵中,获得了243个原肠胚胎,其染色体鉴定表明,29.6%的核移植体的染色体发生了加倍。在另一实验组中,从769个核移植卵得到了5尾2cm以上的个体。尾鳍染色体鉴定、肌肉LDH同工酶电泳和形态鉴别表明,这5尾核移植体为泥鳅雄核发育纯合二倍体。

Studies on unisexual development and homozygous diploid are important in fish genetics and breeding. It is an effective way to purify and improve breeds and to produce monosexual fish. Gynogenesis were successful in many fishes, and gynogenetic homozygous diploid adult fish were obtained. But the reports in relation to fish artificial androgenesis are still rare. Androgenetic haploid loach embryos were produced by mechanically removing female nuclei of Paramisgurnus dabryanus eggs which had been fertilized by loach milt. Transplanting these haploid blastula nuclei into P. dabryanus enucleated eggs resulted in 243 gastrula embryos. Chromosome examination of these nuclear transplants indicated that 29.6% of them had duplicate chromosome number. In another experimental group, 5 adults were obtained from 769 nuclear transplanted eggs. Tail fin chromosome examination, muscle lactate dehydrogenase isoenzyme electrophoresis and morphological character all showed that they were androgenetic homozygous diploid loach. On the basis of the characteristics of fish embryonic mitotic cycle, we are of the opinion that the doubling mechanism of the transplanted haploid nuclei is the presence of a DNA duplication in G2 nuclei after being transplanted into the eggs and then their first cleavage occurs. Due to the fact that the shape of pectoral fins indicated two of the five nuclear transplants being female, we are inclined to believe that the sex determination mechanism of loach is female homogamety and male heterogametry. Discussions concerning the reasons for the high mortality of fish haploid embryos and the possibility of applying the androgenetic homozygous diploid method to fish breeding are presented.