用团头鲂精子诱导金鱼雌核发育研究

INDUCTION OF GYNOGENESIS IN GOLDFISH USING SPERMATOZOA OF BLUNT SNOUT BREAM

用紫外灭活的团头鲂(Megalobrama amblycephala)精子激活金鱼(Carassius auratus Goldfish)卵子,用0—4℃冷水冷休克处理卵子使其染色体加倍,得到成活的雌核发育金鱼。使用与金鱼不同亚科的团头鲂精子作为激活源能极大提高雌核发育后代的鉴定效率,只需依据外形特征、染色体数目和性腺发育程度,就能容易地将雌核发育金鱼和与团头鲂杂交后代区分开。雌核发育金鱼有两种体色不同的后代,但都为双尾,体形似金鱼,染色体数目为2n=100,全雌,性腺发育正常;而杂交后代为单尾,体形似鲫鱼,染色体数目为3n=124,性腺发育滞后。本实验为证明金鱼的性别决定方式为XX/XY型提供了细胞遗传学证据。得到两种体色皆不同于母本体色的后代,可能是基因座位纯化导致后代性状分化,也可能是异精效应导致。

Our previous studies reported that a new triploid fish was produced by crossing the females of goldfish （ Caras- sius auratus Goldfish） with the males of allotetraploid hybrids of red crucian carp （ ♀ ） × common carp （ ♂ ）. Compared this new triploid fish with Xiangyun crucian carp （Japanese crucian carp （ ♀ ） × allotetraploid hybrids （♂ ）, the new type of triploid crucian carp not only presented some advantages which the Xiangyun crucian carp had, such as faster growth rate, wider adaptability, sterility and stronger anti-disease ability, but also got some new good performances like the high ratio of the width to the length of the body and sweet flesh. Goldfish is a kind of the most important species of ornamental fish in China that has centuries-old feeding history, but it has poor capacity of disease resistance and adaptability and so on. As the female parent of the new type triploid hybrids, goldfish was highly expected to be genetically improved. In order to reach the aims, we used sperm from blunt snout bream （Megalobrama amblycephala） which were genetically inactivated by an appropriate UV dosage to activate the development of the egg of goldfish to artificial gynogenesis. In this paper, gynogenetic diploid was induced in goldfish eggs to gynogene- sis using UV-irradiated spermatozoa from blunt snout bream, then the maternal DNA was duplicated with cold shock in the 0--4℃ cold water for 51--58 min to retain the second polar body. The experiment could obtain survivable individuals, and the fertilization rate, hatching rate and survival at the first feeding were （62.7 ± 2.7） % , （30. 1 ± 4.3） % and （6.2 ± 1. 1 ） % , respectively. In this paper, we checked the individuals by morphological characteristics, chromosome number and the degree of gonadal development. Because blunt snout bream and goldfish belong to different subfamilies in zootaxy, using UV-irradiated spermatozoa of blunt snout bream not only can make the evaluation of gynogenetic status more easily, but also more easily to distinguish gynogenetic goldfish from the control hybrids just according to the chromosome number, the morphological characteristics and the degree of gonadal development. The successful gynogenetic goldfish generated offspring with 100 chromosomes, all of which were female that had double tails,looked like the goldfish and ha,t normal gonadal. However, the individuals with 124 chromosomes were generated by hybrids of goldfish x blunt snout bream. They had single tail looked like the crucian, and the gonadal development was delayed. In the present study, it suggested that the spermatozoa of blunt snout bream were an effective activation source for inducing gynogenesis in crucian carp, and we could avoid exploring the genetic markers at the biochemic or molecular levels. This research obtained gynogenetic goldfish that no male was found in all gynogenetic goldfish examined randomly, and the presence of all female gynogenetic diploids matured at one year old provided cell genetics evidence to the goldfish＇s sex determination mode-XX/XY. Furthermore, the gynogenetic individuals had two types of offspring which had two kinds of color that were different from their female parent, and it might be conduced by allele homologizing or by allogynogenesis.