兔痒螨和水牛痒螨第二转录间隔区（ITS-2）基因序列分析

为了探讨水牛痒螨株和兔痒螨株的分类地位，采用 PCR 技术扩增了四川水牛痒螨株和四川兔痒螨株的第二内部转录间隔区（ITS-2）基因，并与 GenBank 中注册的 5 个国外痒螨株的同源基因进行了比较。序列分析发现：兔痒螨株和水牛痒螨株的序列长度分别为 277 bp 和 281 bp，两序列间存在多处转换、颠换和缺失。四川水牛痒螨株同四川兔痒螨株间及国外痒螨分离株间的 ITS-2 基因同源性较低（87.1%～88.0％）； 而四川兔痒螨株与国外痒螨分离株的同源性较高（95.5％～100.0％）。用痒螨 ITS-2 基因构建的 MP，NJ，ME 及 UPGM 树中，兔痒螨株和水牛痒螨株在不同的系统树中其位置比较固定，且两者相距均较远。根据痒螨 ITS-2 基因同源性分析和系统树构建结果以及其他已报道的相关证据，作者认为：兔痒螨株和水牛痒螨株可能为痒螨属 Psoroptes 中两个不同的种，兔痒螨分离株为马痒螨 P. equi ；而水牛痒螨株与来自兔、山羊、绵羊和黄牛等痒螨株亲缘关系较远，可能为痒螨属中的另一个独立有效种。

Nucleotide variation in rDNA ITS-2 differentiates Psoroptes isolates from rabbits and buffalo

To clarify the taxonomic status of Psoroptes isolates from rabbits and buffalo,the second internal transcribed spacer(ITS-2)of the rRNA gene was investigated for the first time based on specimens of two isolates collected from rabbit and buffalo in Sichuan province,S.W.China,and compared with the homologous genes of other five Psoroptes isolates from other countries deposited in GenBank.The results of sequence analysis indicated that the lengths of ITS-2 in rabbit and buffalo isolates were 277 bp and 281 bp,respectively.There were many transitions,transversions and deletions in nucleotide sequences.Homology analyses indicated that the identity levels of nucleotide of ITS-2 between the buffalo isolate from Sichuan and other isolates from abroad ranged from 87.1% to 88.8%,while the gene homology of ITS-2 between the rabbit isolate from Sichuan and other isolates from abroad ranged from 95.5% to 100.0%.The topology of the phylogenetic trees based on ITS-2 gene revealed that the position of Psoroptes isolates from rabbits and buffalo was relatively fixed whether parsimony distance or likelihood methods were used.The phylogenetic analysis showed that the distance between Psoroptes isolates from rabbit and buffalo was relatively far.The results combined with reported evidences suggest that Psoroptes isolates from rabbits and buffalo may be two different species,namely the Psoroptes isolate from rabbit should belong to P.equi,while the Psoroptes isolate from buffalo may be another valid species in Psoroptes.