关键词: 肉食螨, 分子鉴定, COI基因, 18S rRNA基因

Abstract: Objective　To analyze the sequences of mitochondrial cytochrome C oxidase subunit I gene (COI) and 18S ribosomal RNA gene (18S rRNA), so as to identify the feasible DNA barcodes for 4 species of cheyletid mites and improve the DNA barcoding database for cheyletid mites. Methods　Cheyletid mite samples were collected from small?scale flour mills in Fuyang, Wuhu and Tongling cities of Anhui Province from May 2018 to July 2019, extracted and morphologically identified. Then, genomic DNA was extracted from a single cheyletid mite, and the COI and 18S rRNA gene sequences were obtained by PCR amplification, cloning and sequencing. The obtained sequences were aligned using the BLAST software. Multiple sequence alignment was done using the software ClustalX version 1.83 using the known gene sequences from cheyletid mites. The genetic distance was calculated using the software MEGA X, and the phylogenetic tree was created using the maximum likelihood method. Results　The DNA barcoding results of Cheyletus malaccensis, C. carnifex and Cheletomorpha lepidopterorum were consistent with the morphological identification, while no sequences pertaining to Eucheyletia reticulate were retrieved in the GenBank database. The proportions of A + T were 69.6% and 55.1% in the COI and 18S rRNA sequences of 4 cheyletid mites species, respectively, and the numbers of base substitutions were 137 and 46, respectively. There were 154 to 321 and 58 to 99 inter?species variation loci in the COI and 18S rRNA gene sequences of 4 cheyletid mites species, respectively, and the intra?species genetic distance was all 0.020 or less in the COI and 18S rRNA gene sequences of 4 cheyletid mites species, with inter?species genetic distance of 0.235 to 0.583 and 0.078 to 0.114, respectively. Phylogenetic analysis based on COI and 18S rRNA genes showed that all four species of cheyletid mites were clustered into a branch with a 100% supportive rate, which was consistent with the morphological identification. Conclusion　Mitochondrial COI gene is superior to 18S rRNA gene as DNA barcodes for 4 species of cheyletid mites, which is more suitable to be used to investigate the phylogenetic relationship of at genus and species levels.

Key words: Cheyletid mite, Molecular identification, COI gene, 18S rRNA gene