Studies On The Formation And Biological Characteristics Of Progeny Of Female Cyprinus Carpio×Male Xenocypris Davidi Bleeker

Distant hybridization refers to the hybridization between species,genera or even distantly related species,leading to changes in the genotype and phenotype of their offspring.Generally,distant hybridization is an important technique in fish genetic breeding.In this study,a new homodiploid red crucian carp(NRCC)was successfully obtained in the hybridization of common carp(Cyprinus carpio,2n=100)(♀)and Bleeker’s yellow tailed(Xenocypris Davidi Bleeker,2n=48)(♂).The studies of appearance characteristics,chromosome number,fluorescence in situ hybridization(FISH),and molecular genetics of offspring were investigated as follows.1.The morphological characteristics and reproductive characteristics of the offspring derived from the hybridization of female common carp and male Bleeker’s yellow tailed were studied.The phenotypes characterizes of NRCC were very similar to red crucian carp(Carassius carassius red var.,RCC,2n=100).In terms of reproductive characteristics,the gonadal tissues of 10-month-old NRCC were observed in paraffin sections.The ovaries of female NRCC developed normally,in which a large number of oocytes of stage III were found;and a large number of normal spermatid was found in spermatozoa of male NRCC.Regarding the reproductive traits,the gonad of NRCC developed normally.2.Biological characteristics including the chromosome number and DNA content of NRCC were investigated.The results of chromosomal preparations and flow cytometry showed that the chromosome number of the NRCC was 100,which was consistent with the chromosome number of the COC;and the average DNA content of NRCC was not statistically significantly different from that of COC(P > 0.05),and was significantly different from that of YT(P < 0.05).In summary,it can be determined that NRCC was diploid with 100 chromosomes.3.5S r DNA(340bp,GQ485556)was used as a probe for fluorescence in situ hybridization(FISH)of the chromosomal split phases of NRCC.The results showed two strong fluorescence signals and two fluorescence weak signals were stably labeled in chromosome of NRCC,which was consistent with the fluorescence signal of red crucian carp,while no fluorescence signal was detected in COC and YT.4.The structural variation of mitochondrial genome sequences of NRCC was analyzed.The results showed that the mitochondrial sequence of NRCC underwent large genetic variation,but meanwhile a large of insertions and deletions of base fragments of YT also were found in the mitochondrial DNA of NRCC,indicating the mitochondrial genes of NRCC occurred larger proportion of chimerism.5.The structural variation of the genomic DNA(5S r DNA,18 S r DNA and Hox genes)of COC,YT and NRCC were investigated.The results showed that the 18 S r DNA gene sequence structure of NRCC was more similar to COC,and differed significantly from YT,reflecting the maternal origin of NRCC.Meanwhile,the mutations were found in the5 S r DNA and Hox gene sequence structure in NRCC,and the gene sequence structure of NRCC derived from the COC and the YT was recombined,reflecting larger variation of NRCC at the level of genomic DNA.In this study,NRCC were successfully prepared from the cross of common carp(♀)and Bleeker’s yellow tail(♂),and its biological characteristics were systematically study,providing new experimental materials and important biological data for fish genetic breeding research and also providing important molecular biological evidence for the evolution of common carp into crucian carp through distant hybridization.