人工诱导雌核发育牙鲆的染色体及核型证明

CHROMOSOME AND KARYOTYPE EVIDENCE OF ARTIFICIAL-INDUCED GYNOGENESIS IN THE OLIVE FLOUNDER PARALICHTHYS OLIVACEUS(T.ET S.)

于1994-1996年，分别在威海海洋渔业捕捞公司（石岛）和鸿洋实业总公司龙须岛育苗场采集人工培育的3－5龄牙鲆亲鱼，采用紫外线照射法使牙鲆精子遗传物质失活，并用冷休克法抑制受精卵第二极体释放，从而获得雌核发育二倍体牙好。原肠期采用空气干燥法、Giemsa染色，得到雌核发育二倍体、正常二倍体及单倍体的染色体制片，进行染色体和核型的分析。结果表明，牙鲆的雌核发育二倍体和正常二倍体的染色体数均为2n=48，核型为48t，即48条端部着色点染色体，臂数NF=48，两者的核型设有明显差异；单倍体为24条端部着丝点染色体；在3个组别中，第一号染色体上都有一明显的次缢痕。雌核发育二倍体牙鲆的诱导率为98％。

Since there exist obvious growth differences between the male and female olive flounder,i. e., the female grows faster than the male, and the number of the female is smaller than the male,the production of the olive flounder is liwhted. Gynogenesis is considered to be an efficient methodto solve these problems. For this purpose, gynogenehc induchon of the olive flounder was canedout by cold shock 3at4min after activation of the eggs with sperm which had been inastivated withUV irradiation during 1994 to 1996. The normal diploidy, gynogenetic dip1oidy and haploidy oliveflounder were obtrined and cultured under normal condihons. Chrmosome samples of the taegroups were prepared by airidried method. Observahons and analyses of chromosome spreads showthat there are 48 acrocentric chromosomes in both normal and gynogenetic diploid. Their karyotypeformula were 48t NF = 48. In haploid there were 24 acrocentric chromosomes. A secondaryconstriction was observed in No. l chromosomes in all groups. There was no obvious difference inkaryotype between normal and gynogenetic diploids.The sex determination in olive flounder is of the female homogametic (XX) and maletieterogametic (XY) type. Manipulation of such a system using gynogenesis gives diploid fish thatare both genehcally and phenotypically female, because the homogamehc haploid gynogenetics isproduced when the irradiated sperm is used to fenilize eggs, and diploidisation of the gynogeneticgenome is achieved by temperature shocks. The present study also shows that the induction rate ofthe gynogenetic diploid in olive flounder was 98%; elsewhere, it was reported that a 1OO%preduchon of all-female gynogenesis was obtrined in the same species in Japan. The failure toproduce 100% gynogenesis might be due to the limited conditions of treatment of sperm. By theoptimization of inducing conditions, the results may be further improved.