Studies On The Genetic And Reproductive Characteristics Of Artificial Hybrid Triploid Crucian Carp

A kind of hybrid triploid fish have been obtained by hybridization of female autotetraploid fish(4nRR,4n=200)and male goldfish(Carassius auratus var.,GF,2n=100),which was named artificial hybrid triploid crucian carp.The fertility of male and female artificial hybrid triploid crucian carp was different.Male artificial hybrid triploid crucian carp was fertile and the female was sterile.In this study,the ploidy,morphological traits,genetic and reproductive characteristics of this artificial hybrid triploid crucian carp were studied.The main research contents and results are as follows:1.The ploidy and the number of chromosomes of artificial hybrid triploid crucian carp were detected by flow cytometry DNA content and chromosome preparation with the peripheral blood lymphocyte.The results indicated that the mean of DNA content was 153.52,1.5 times that of the diploid goldfish,and the number of chromosomes was 150,indicating that it was a triploid fish.2.The results of morphological traits indicated that artificial hybrid triploid crucian carp was inclined to maternal autotetraploid fish in shape.Comparing with the maternal autotetraploid fish,except for the ratio of head height to head length and head height to body height,there was no significant difference in other measurable traits(P>0.05).Comparing with the goldfish,all the ratio of measurable traits showed significantdifferences(P<0.05).The major countable traits of artificial hybrid triploid crucian carp were between autotetraploid fish and goldfish,which showed hybrid characteristics.3.The fertility of one-year-old artificial hybrid triploid crucian carp was researched.It was found that ovarian development was normal and mature eggs could be produced during the breeding season.However,testis development was abnormal and sperm with normal function could not be produced.In-depth study on the characteristics of one-year-old sterile male artificial hybrid triploid crucian carp revealed that the testis contained spermatogonia,spermatocytes and sperm cells,but there was no mature sperm;a large number of apoptosis signals in the testis were located in sperm cells;The results of real time PCR showed that the expression levels of p53,the apoptotic gene,in the testis of one-year-old artificial hybrid triploid crucian carp was higher than that of other tissues.The meiosis-related genes,spo11,dmc1 and rad51,had normal expression levels in the ovary and higher expression levels in the testis than that of red crucian carp.spef2 and dnah3 had lower expression levels in testis of one-year-old artificial hybrid triploid crucian carp than that of red crucian carp.4.The structures of 5S rDNA and sox gene were analyzed.It was found that goldfish contained four different sizes of 5S rDNA structural units of 168 bp,203bp,340 bp and 490 bp.The maternal autotetraploid fishcontained three 5S rDNA structural units with 203 bp,340bp and 486 bp respectively.The artificial hybrid triploid crucian carp had three 5S rDNA structural units,the size of which was 203 bp,340bp and 495 bp respectively.During the hybridization process,the progeny inherited the partial 5S rDNA structural unit of the parents,and also lost the fragment of 168 bp that was paternal unique 5S rDNA structural unit,showing obvious recombination and variability.The genetic analysis of the sox genes showed that artificial hybrid triploid crucian carp had the same sox gene bands with its female parent that were 215 bp,616bp,918 bp and1959bp respectively.The goldfish had three bands that were 215 bp,616bp and 1953 bp respectively.In summary,the artificial hybrid triploid crucian carp had special reproductive characteristics that the female was fertile and the male was sterile.Therefore,in-depth study of the inheritance and reproduction characteristics of the artificial hybrid triploid crucian carp was of great significance in the evolution of fish reproduction.