Morphology And ITS-2 Sequences Study Of Mites Of The Genus Chorioptes From Different Host (Acari: Psoroptidae)

Chorioptes mites have a worldwide distribution and are the most common causative agents of mange in horses,cattle,goats,sheep,rabbits,giant panda and so on. As has been already extensively reviewed, Chorioptes mites should be divide into Chorioptes bovis and Chorioptes texanus according to detailed biological and morphological studies, but some scholar didn't agree with that. Because it is necessary to consider the knowledge of the taxonomy of the genus Chorioptes by reviewing the literature on various taxonomic criteria, including molecular biological data. Some questionable Chorioptes spp, such as C. crewei, C.mydaus and C.panda and so on, their validity is questionable.Five Chorioptes isolates from five host species in three places of the China (Chorioptes from Chinese Holstein cow,Simmental cow,Montbeliarde cow in Hongya,Chorioptes from Chinese cattle in Shuangliu and Chorioptes from giant panda in Wolong) was investigated to clarify the taxonomic status of mites of the genus Chorioptes. First, the morphology of Chorioptes mites from Chinese cattle and giant panda were observed by optical microscopy and scanning electron microscopy, Second, the rDNA second internal transcribed spacer(ITS-2) gene was characterized in 5 Chorioptes isolates. Morphology result shown: all of the 5 isolates male mites are provided with paired opisthosomal lobes, each consisting of a primary lobe with an outer, smaller secondary lobe. The lengths of spatulate setae and outer fine setae of those mites are about 168—255μm and 43—80μm. The body of mites from giant panda was larger than that of from Chinese cattle. The whole ITS-2 sequence of Chorioptes isolates from giant panda was 232bp (longer than that of C.bovis and C.texanus). The homology of those with AF123081 and AF123082 were 90.4% and 85.6%. The whole ITS-2 genes of Chorioptes isolates from Chinese Holstein cow,Montbeliarde cow in Hongya and Chinese cattle were 225bp and the whole ITS-2 genes of Chorioptes isolates from Simmental cow was 228bp. The homology of those four ITS-2 sequences with AF123082 were between 94.2% to 97.8%, but only 84.3% to 87.0% with AF123081.In addition to the five ITS-2 sequences, the ITS-2 sequences of Psoroptes cuniculi (AB105201), the ITS-2 sequences of C. texanus (AF123082) and the ITS-2 sequences of C. bovis (AF123081) were obtained from Genbank. The MEGA2.0 software was used to make cladogram and determine the genetic relationship among of 8 mites species using ITS-2 sequences. Result shown that the highest genetic relationship were found between C1 and C3 as well as between C2 and C. texanus (AF 123082). There was low genetic relationship between C5 and C.bovis (AF 123081) as well as between C5 and C.texanus.On the basis of morphological characterization and genetic relationship, the Chorioptes mites from giant panda (C5) should belong to neither C. texanus nor belong to C.bovis. Chorioptes panda should be a valid species in Chorioptes. C1,C2,C3 and C4 should be C.texanus.