Study On The Morphology Of The First Generation Of Showa Koi And Longtail Goldfish Roe

Distant hybridization refers to the interspecific or interspecific hybridization of two or more species with each other.It can combine the genomes of different species so that the offspring of hybrids have significant changes in phenotype and genotype,forming offspring with heterosis.Through distant crosses of Showa koi(Cyprinus carpio haematopterus)and longtail goldfish(Carassius auratus Linnaeus),the crossed progeny of the orthogonal group(Longtail Gold female ♀)and crossed progeny of the reverse cross-group(Showa koi female ♀)were obtained.The main research contents of this paper include:(1)The morphological characteristics of the hybrid fish in the orthogonal group and the hybrid fish in the reverse cross-group were analyzed by statistics.The quality traits were skin markings(2 types: with markings,no markings);mouth position(2types: front Mouth position,lower mouth position);whiskers(3 species: no whiskers,one pair of whiskers,two pairs of whiskers);scale color(6 species: yellow,black,red,blue,white,mixed);fish belly color(4 types: yellow,white,red,hybrid);fin color(4types: yellow,red,black,mixed);sclera color(3 types: black,yellow,red);body size(2 types: spindle,Body shape variation);caudal fin traits(1 species: fork-shaped tail),quantifiable traits are body length,full length,tail length,body height,caudal peduncle length,caudal peduncle height,head height,head length,and the body length is obtained by calculation.Length/full length,tail length/total length,body height/body length,body height/head height,tail peduncle height/tail stalk length,head height/head length.The countable characters of the hybrid fish in the orthogonal group and the reverse cross-group were recorded: the number of dorsal fin rays,the number of analfin rays,the lateral line scale,the lateral line scale,and the lateral line below the scale.The results showed that most of the traits of the hybrid offspring were more similar to the female parent.The genetic material of the female parent was more influential in the development and growth of the offspring,regardless of the cross-breeding group or the cross-breeding group.In pattern body-color traits,the hybrid fish were more similar to the female parent.The ratio of quantifiable traits reflected that the backcross hybrid fish was more similar to the female parent.The whisker traits were highly similar to the female parent.However,the insertion of the male parent gene will also affect the traits of the hybrid offspring.For example,in the whisker traits,the orthogonal hybrid fish is closer to the male parent,and its body length/total length,head height/head length,and tail length/total length.The length ratio is also closer to the male parent,with a shorter head,longer body,and a body shape more similar to the male parent koi.The red sclera is considered a symbol of albinos in the sclera color,and changes in physiology,environment,and genetics can cause albinos.6,the number of red sclera traits in the reverse cross-group was twice that of the orthogonal group,indicating that the gene recombination in the reverse cross-group was much more severe.According to the observation results of paraffin sections made of part of the gonads of the hybrid fish in the orthogonal group and the reverse cross-group,most of the female fish in the orthogonal group had hermaphroditic ovaries,and some of the ovaries were retarded.Abortion or all abortions,the male fish did not appear in the testis of hermaphroditic chimera,and the semen could be squeezed out during the breeding period.The preliminary judgment was that the male was fertile.In the hybrid fish of the reverse cross-group,some females had hermaphroditic testis,and some had mature yolks.It was speculated that the females were partially fertile,and the males were partially fertile.(2)Using GBS(Genotyping-by-sequencing)sequencing technology,the single nucleus of 1 Showa koi,one longtail goldfish,six orthogonal group hybrid fish,and nine reverse cross-group hybrid fish were screened.Sequencing library construction and genotyping at single nucleotide polymorphism(SNP)sites,analysis of the genetic relationship between hybrid progeny and parents,and genetic diversity of hybrid progeny for the follow-up koi and goldfish molecules Marker-assisted breeding provides the basis for our study.The results showed that among the 17 samples,the constructed reference genome contained a total of 1,574,782 sequences.The average sequencing depth of all samples was 25.43×.After mutation site detection and filtering,686,540 SNP sites were obtained.According to the phylogenetic tree results,most of the hybrid fish in the orthogonal group are more inclined toward the female parent Goldfish.Most hybrid fish in the reverse cross-group are more inclined to the female parent Showa koi in the blood relationship.There are exceptions.The albino sample is closer to the male parent than the standard sample in orthogonal.In the reverse crosshybridization group,the body color was black,and the two pairs of whiskers were more closely related to the male parent.Conclusion:(1)Regardless of the cross-cross hybrid fish,most of the traits of the hybrid offspring are more inclined to the female parent,and the hybrid fish is closer to the female parent.(2)From the morphological point of view,the sample diversity of the hybrid fish in the reverse cross-group is stronger than that of the orthogonal hybrid fish.(3)The females of the orthotopic hybrid fish were all aborted or partially aborted,speculating that the males were fertile.The females were partially fertile among the hybrid fish in the reverse cross-group,and the males were completely or partially aborted.(4)It is verified that most traits of the hybrid offspring are more inclined to the female parent regardless of the orthogonal cross because the genetic material of the female parent is more influential in the development and growth of the offspring.