Crucian Carp F <sub> 1 </ Sub> And F <sub> 2 </ Sub> Self-fertilization, Cytology And Allotetraploid Origin,

This paper presents the studies of cytological behavior of autocopulation fertilization of F1 F2 hybrids of Red crucian( ) X Common carp() by means of light-inicroscope.The results are generalized as follows:The diameter of mature oocytes of F1 hybrid is between 1.0-1.25mm,which that of F2 hybrid is roughly divided into three types:1.3mm, 1.7mm,2.0nim.The mature eggs of F1,F2 hybrids stay at the metaphase of secondary maturation division before fertilization,with a micropyle through which usually only single sperm is allowed to penetrate.Normal spenn is available from the male and female F1 F2 hybrids which are partially fertile . F1,F2 hybrids comply with the pattern of monospermism,also with the normal process of fertilization.Firstly,the study on autocopulation fertilization of FI hybrid was conducted.ln the surroundings of 18-20C of the water temperature,the spennaster was appeared obviously and the elimination of the second polar body was accomplished at 5~15 minutes after fertilization.By the 15 minutespostinsemination,the male and female pronuclei were formed,and subsequently,they moved toward the center of blastodisc,then contacted with each other,lastly fused completely to be the zygotic nucleus.The first cleavage occurred at about 40 minutes after fertilization,when a tripolar spindle was found in a section of one zygote.Secondly, the study on autocopulation of F2 hybrid also was perfonned.In the same condition of water temperature,the appearance, of spcrmaster and the extrusion of the second polar body were observed at 18 minutes after insemination,By 28 minutes postinsemination,the formation of male and female pronuclei were found.At 53 minutes after feitilization,the male and female pronuclei were merged,then first segmentation occurred at 65 minutes postinsemination.the interval between the successive divisions is about 15~20minutes.All in all,the autocopulation fertilization of F1, F2 hybrids agrees with the general fertilization laws,it is concluded that allotetraploid fish (F3) was produced by the fertilization between diploid spermatozoa and diploid eggs produced by F2. In addition, the present paper discusses the reason why diploid gametes in F2 was produced, and why the allotetraploids can produced next generations steadily in gene and phenotype.