Abstract
BackgroundThe morphological and molecular identification of mites is challenging due to the large number of species, the microscopic size of the organisms, diverse phenotypes of the same species, similar morphology of different species and a shortage of molecular data.MethodsNine medically important mite species belonging to six families, i.e. Demodex folliculorum, D. brevis, D. canis, D. caprae, Sarcoptes scabiei canis, Psoroptes cuniculi, Dermatophagoides farinae, Cheyletus malaccensis and Ornithonyssus bacoti, were collected and subjected to DNA barcoding. Sequences of cox1, 16S and 12S mtDNA, as well as ITS, 18S and 28S rDNA from mites were retrieved from GenBank and used as candidate genes. Sequence alignment and analysis identified 28S rDNA as the suitable target gene. Subsequently, universal primers of divergent domains were designed for molecular identification of 125 mite samples. Finally, the universality of the divergent domains with high identification efficiency was evaluated in Acari to screen DNA barcodes for mites.ResultsDomains D5 (67.65%), D6 (62.71%) and D8 (77.59%) of the 28S rRNA gene had a significantly higher sequencing success rate, compared to domains D2 (19.20%), D3 (20.00%) and D7 (15.12%). The successful divergent domains all matched the closely-related species in GenBank with an identity of 74–100% and a coverage rate of 92–100%. Phylogenetic analysis also supported this result. Moreover, the three divergent domains had their own advantages. D5 had the lowest intraspecies divergence (0–1.26%), D6 had the maximum barcoding gap (10.54%) and the shortest sequence length (192–241 bp), and D8 had the longest indels (241 bp). Further universality analysis showed that the primers of the three divergent domains were suitable for identification across 225 species of 40 families in Acari.ConclusionsThis study confirmed that domains D5, D6 and D8 of 28S rDNA are universal DNA barcodes for molecular classification and identification of mites. 28S rDNA, as a powerful supplement for cox1 mtDNA 5’-end 648-bp fragment, recommended by the International Barcode of Life (IBOL), will provide great potential in molecular identification of mites in future studies because of its universality.
Highlights
The morphological and molecular identification of mites is challenging due to the large number of species, the microscopic size of the organisms, diverse phenotypes of the same species, similar morphology of differ‐ ent species and a shortage of molecular data
Some mites were directly classified according to their parasitic habitats and hosts, including Ornithonyssus bacoti from rat-lingering areas [10], Psoroptes cuniculi isolated from the external auditory canal of rabbits [36], Sarcoptes scabiei canis [26], Demodex canis [37] collected from dogs suffering from mange and demodicosis, and D. caprae isolated from skin nodules of goats [38]
Collection and morphological classification of mites A total of nine medically important mite species were obtained in this study, including D. farinae, P. cuniculi, S. canis, O. bacoti, C. malaccensis, and D. folliculorum, D. brevis, D. canis and D. caprae
Summary
The morphological and molecular identification of mites is challenging due to the large number of species, the microscopic size of the organisms, diverse phenotypes of the same species, similar morphology of differ‐ ent species and a shortage of molecular data. The classification of mites has mainly been dependent on morphological characteristics and/or parasitic hosts. This field has been facing challenges due to the large number of species, the microscopic size of the organisms, diverse phenotypes of the same species, similar morphology of different species, and a shortage of specialized taxonomists [1,2,3]. In order to take targeted measures to control mite-borne diseases, it is extremely important to distinguish medically important mites effectively
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