Comparative Studies On The Spermatogenesis And Its Mechanism Of "Triploidy" And Diploidy Crucian Carp

Carassius auratus gibelio Bloch belongs to Cyprinidae, Cyprininae, Carassius. The cruciancarp was a very popular breed in the fishery product market, because it tasted well and grewfast. Thus the crucian carp becoming a significant economical fish for aquaculture in China whichis not only in the natural waters but also in the fresh-water ponds. In 2005, the production of thecrucian carp is about 15％of the cultural production in the ponds. The crucian carp in Heilongjiangwaters was considered to be Carassius auratus gibelio Bloch. Which distribute in the rivers wasregarded as diploid has 100 chromosomes in somatic cells mostly, and it reproduces byamphigenesis has regular sex ratio in the population. The population distributed in the lakes andreservoirs was regarded as "triploid" with 150±chromosomes in somatic cells, and itreproduced by gynogenesis. There were only 5％～20％males in this population.Spermary histological structures and spermatogenesis of "triploid" and diploid in the Cruciancarp (Carassius auratus gibelio Bloch) were investigated by means of light microscope andtransmission electron microscope. The sex mechanism, the evolution of triploid and the role ofmales in the gynogenesis population were discussed thoroughly.The results indicated no abnormalities were found in spermatogenesis of the "triploid", and itsspermary which is similar to the diploid is lobular type which constituted by out membrane andparenchyma. The Seminiferous lobules are composed of several cysts and distribute inradiation. The spermatocyte and immature spermatid located in the spermatogenic cysts, afterspermatozoa have matured, the spermatozoa were released into lumen of seminiferous Iobula out ofthe spermatogenic cysts. The spermatogenesis was clear that Spermatogonium, primaryspermatocyte, secondary spermatocyte and Spermatid in each developmental stage were found in"triploid" and diploid in Crucian carp by both light microscope and transmission electronmicroscope. However, the volumes of germocytes with each developmental stage in "triploid"and diploid were different, its proportion was 2 : 3 in principle, because of the difference ofchromosome numbers. There was no distinction in the Spermiogenesis, but the volume of maturedspermatozoa in the diploid were less than those in the "tripioid"; the density of of maturedspermatozoa in the "triploid" were less than those in the diploid obviously.The results indicated that "triploid" population in the Crucian carp(Carassius auratus gibelio)had acertain ratio of males indeed, their chromosome number was similar with the females which reproduces by gynogenesis. The spermatogenesis of the males in the "triploid" and the biologicactivity of the spermatozoa were ordinary. Therefore, the "triploid" could produce normal maturespermatozoa after meiosis.The normal spermatogenesis in the "tripioid" proved that the Crucian carp has thecharacteristic of aniopioidy which has 150±chromosomes in somatic cells. Due to having maturespermatozoa, the males in the "triploid" play a very important role in the population thatreproduces by gynogenesis. The crucian carp may have reproduced gynogenetically beforediploidization but has now become diploid in behaviour. The change of reproductive form might bea long transition period. The males in the diploid was considered as tetraplont; The males in the"triploid" is fertile and could form mature spermatozoa after meiosis, which was regarded ashexaploid, they were undergoing the course of diploidization.