Molecular Biological Evidence For The Development Of Goldfish By Distant Hybridization Of Carp

Distant hybridization makes it possible to transfer the genome from one species to another,which results in changes of phenotypes and genotypes in hybrid progenies.In present study,Goldfish-like fish with twin tails?GF-L;2n=100?was produced by self-mating of Red crucian carp-like fish?RCC-L;2n=100?,which derived from the distant crossing of koi carp?Cyprinus carpio haematopterus,KOC;2n=100;??and blunt snout bream?Megalobrama amblycephala,BSB;2n=48;??.At present,GF-L had been steadily bred to the fourth generation?F₄?.By the survey of genetic and other biological characteristics in GF-L,We preliminarily explored that KOC evolved into GF through distant hybridization in this study.The specific research contents are as follows:1.In terms of phenotypes characteristics,the body color of GF-L is similar to that of KOC,but the twin tail of GF-L is significantly different from that of KOC,BSB and RCC-L.In terms of the measurable traits and the countable traits,the morphological characteristics of GF-L and parents showed significant difference?P<0.05?,but the morphological characteristics of GF-L showed no significant difference?P>0.05?to normal goldfish?GF?.2.In the ploidy level,through the analyses of blood cells,chromosomes and flow cytometry,it was found that there were no obvious dumbbell-type cell in the blood cells of GF-L,the number of chromosomes was 100,and the DNA content was 100.The results showed that the GF-L was a diploid fish3.In terms of genetic characteristics,the nucleotide sequences of 5S rDNA and ITS region of 45S rDNA in genomic DNA of GF-L,RCC-L and their parents were analyzed.The results showed significant sequence difference between RCC-L and GF-L.The sequence similarity between GF-L and GF is higher than that in GF-L and KOC or BSB.The 5S rDNA of GF-L and RCC-L were mapped to the genomes of CC and BSB,and the results revealed that the average similarities of GF-L and RCC-L to CC were higher than those to BSB,supporting that GF-L and RCC-L were homodiploids that were mainly derived from the genome of KOC.Comparative analysis regarding chordinA gene in GF-L and RCC-L revealed that the presence of a twin tail in GF-L may related to a base mutation,which presented G in RCC-L but T in GF-L.These results provided direct evidence of the KOC into the GF evolutionary pathway that was triggered by distant hybridization,the KOC into the GF.4.For the reproductive traits,the survival rate of GF-L was 76.3%,which was higher than that in RCC-L.The paraffin section of gonadal in GF-L showed that mature oocytes and mature sperm cells were found.so it could be inferred that in the process of transformation of carp into GF through distant hybridization,offspring GF-L had the characteristics of sexual fertility and steadily bred to the fourth generation?F₄?.This study proves that the hybridization between KOC and BSB is a way to obtain Goldfish,which had important significance in evolutionary biology and genetic breeding.