Study On The Genetic Property Of F₉-F₁₂ Allotetraploid And The Gynogenensis,Androgenesis Of Allotetraploid

The formation of the population of the allotetraploid hybrids of red crucian carp and common carp is the first case in the world which both the female and the male of allotetraploids are fertile, they are the good materials for studying the biological characteristic of tetraploid animals, this paper reports the hereditary characters of allotetraploids including the stability of hereditary gynogenesis and androgenesis.I.The chromosome number and gonadal structure of F₉-F₁2 a 11otetrapIo i d hybr i dsIn this paper, the chromosome number of of F₉-F₁2 of hybridis of Red crucian Carassius auratus () × common carp Cryprinus carpio () were examined by means of kidney cell-PHA culture. The results show that F9-F₁2 allotetraploida still possessed 200 chromosomes, with the karyotype formula 44m+68sm+44st+44t, which were the same as the data indicated in F₃-F₈ allotetraploids. The females and males of F₉-F₁2 possessed, respectively, the normal ovaries and testes that were able to produce the normal dipoid ova and sperm, respectively. With ultramicrotomy ,we observed the structure of the ovary and testis of allotetraploids, the mature testis are composed of lots of seminiferous tubules, which filled with spermatogoniunu spermatid and sperm, the diploid sperm consists of the head and the tail , the head is full of the dense chromatin, the central structure of tail is axial fiber with the "9+2" microtubules. There are lots of microvilli in the stage IVand V oocyte of the mature ovary, which stick into the zona pellucida, we concluded the function of the microvilli is exchanging the substance and singal. There aretwo yolksexist in the stage IVand Voocyte in two forms, one is the intravesicle yolk, the other is the extravesicle yolk. In nature conditions, without the injection of the extraneous hormone, the females and males of F₉-F₁2 could mate each other to produce new next generation of tetraploids. With the stable genetic tetraploidy and the fertility in the nature environments, this allotetraploid population possessed the key factors to form a new species with 200 chromosomes.2. The gynogenesis of allotetraploid hybridsWithout the treatment to double the chromosome number, the diploid eggs produced by the females of tetraploid hybrids of red crucian carpX common carp were able to develop to living diploid fish after subjecting to activation of the UV-irradiated sperm. With the cold shock, the diploid eggs also developed to diploid gynogens after the activation of the UV-irradiated sperm, no tetraploid gynogens being found, suggesting that it is difficult to double the chromosome from the diploid to tetraploid by means of cold shock treatment. The hatching rate of the gynogens with the cold shock was higher than that of the untreated gynogens. All the gyngens with and without cold shock were examined to be diploid females with 100 chromosomes, providing the evidence that the females of the tetraploid population are homogamety (xxx). The mature females were only found among the two-year old gynogens, not being found among the one-year old gynogens, indicating that the ovary in the gynogens developed slowlier than that in the normal diploids such as the red crucian carp. Thirty percent of the gynogens were fertile which possessed the normal ovary and produced normal mature eggs. The appearance of the gynogenetic fish was similar to that of F2 hybrids, the diploidgynogens were able to produce diploid eggs that were proved by the presence of the triploids with 150 chromosomes among the offspring produced by mating the diploid females of the gynogens with the diploid males of the red crucian carp. As the control group, the diploid eggs fertilized with the haploid sperm of the scatter scale carp developed to triploid hybrids. The possible sex-determining types of the tetraploid population were also discussed in the present study. 3. The androgenesis of a Ilotetraploid hybridsIn 2002, the goldfish' s female nucleus were inacted by using UV rays to irradiate the eggs, the diploid s...