RAPD-SCAR marker and genetic relationship analysis of three Demodex species (Acari: Demodicidae).

For a long time, classification of Demodex mites has been mainly based on their hosts and phenotype characteristics. The study was the first to conduct molecular identification and genetic relationship analysis for six isolates of three Demodex species by random amplified polymorphic DNA (RAPD) and sequence-characterized amplified region (SCAR) marker. Totally, 239 DNA fragments were amplified from six Demodex isolates with 10 random primers in RAPD, of which 165 were polymorphic. Using a single primer, at least five fragments and at most 40 in the six isolates were amplified, whereas within a single isolate, a range of 35-49 fragments were amplified. DNA fingerprints of primers CZ 1-9 revealed intra- and interspecies difference in six Demodex isolates, whereas primer CZ 10 only revealed interspecies difference. The genetic distance and dendrogram showed the intraspecific genetic distances were closer than the interspecific genetic distances. The interspecific genetic distances of Demodex folliculorum and Demodex canis (0.7931-0.8140) were shorter than that of Demodex brevis and D. canis (0.8182-0.8987). The RAPD-SCAR marker displayed primer CZ 10 could be applied to identify the three Demodex species. The 479-bp fragment was specific for D. brevis, and the 261-bp fragment was specific for D. canis. The conclusion was that the RAPD-SCAR multi-marker was effective in molecular identification of three Demodex species. The genetic relationship between D. folliculorum and D. canis was nearer than that between D. folliculorum and D. brevis.