The Study On Skin Histology, Melanin-concentrating Hormone Receptor And Cytochrome B Gene In Different Body-color Of Carassius Auratus Var. Pingxiangnensis

Chromatophore of scale and skin from four phenotypes(complete black,half black,piebald,and whole red) of Pingxiang Red-transparent Crucian Carp (Carassius auratus var.pingxiangnensis) was observed through optical microscope, the histological structure of the skin was also studied.The partial fragments of MCH receptor gene were cloned,and their distribution and expression in tissues were studied by the method of fluorescence quantitative PCR.The Cyt b gene was cloned, and the phylogenetic position was also analyzed and compared.1.The scale and skin from four phenotypes of Pingxiang Red-transparent Crucian Carp were observed based on optical microscope,found to contain only three pigment cells in the scale which are melancphore,xanthophore and iridophore, while the skin contains only melanophore and xanthophore.The pigment cells' distribution of scale and skin from different phenotypes of the fish are different, especially in the form of melanocytes' distribution.The skin of complete red indivdual was observed by conventional paraffin section technique and found that the pigment cells not only exist between dermis and epidermis,dermis and subcutaneous layer,but also in the gland layer and subcutaneous layer.2.2 gene of the partial fragment of MCH receptor which contains a partial encoding region of 366 bp,and 122 amino acid residues was cloned.Fluorescence quantitative PCR was uesd to detect the distribution of MCHR2 gene in tissues of the complete red phenotype fish,as well as the distribution in four phenotypes of the fish's brain and skin tissues.The result indicated that there is a highest expression in liver,while lowest in the kidney,followed by eye,muscle,gill,brain, intestine and heart;There was no significant difference during the expression of MCHR2 in the brain tissues of four phenotypes,but significant differences in the skin tissues between whole red phenotype and complete black phenotype,while no significant difference between the whole red phenotype and the piebald and the half black phenotype.3.The partial fragment of MCHR1a gene and MCHR1b gene were cloned,and there is 96%of homology based on the biological software BALST,and the expression and distribution of them in tissues were found basically identical.Therefore,we think that the MCHR1a gene and MCHR1b gene is the same gene,renamed MCHR1,that is,there is no gene differentiation in MCHR1.The partial fragment of MCHR1 gene was obtained by the splicing,which contains a partial encoding region of 481 bp,and 160 amino acid residues.4.The entire coding sequence of mitochondrial cytochrome b gene of four phenotypes of Pingxiang Red-transparent Crucian Carp was cloned and found that its sequence exactly the same,including the length of 1140 bp and 380 amino acid residues.The result suggested that there is no change in the molecular level,and also no subspecies in the fish,despite the phenotype differences in some individual. The result of phylogenetic tree which was constructed by neighbor joining method indicated that there is the closest phylogenetic relationship between the Pingxiang Red-transparent Crucian Carp and the Common Crucian Carp.