Search

Molecular identification of acaroid mites is difficult because of the scarcity of molecular data in GenBank. Here, acaroid mites collected from ground flour dust in Xi'an, China, were preliminarily morphologically classified/grouped. Universal primers were then designed to amplify and screen suitable DNA barcodes for identifying these mites. Sixty mite samples were morphologically classified into six groups. Groups 1-2 were identified to Dermatophagoides farinae and Tyrophagus putrescentiae, while Groups 3-6 were not identified to the species level. ITS2 exhibited higher efficiency in molecular identification in comparison with COI, 12S, and 16S. Groups 1-6 were identified as D. farinae, T. putrescentiae, Suidasia nesbitti, Chortoglyphus arcuatus, Lepidoglyphus destructor, and Gohieria sp., respectively. The phylogenetic results were consistent with the morphological classification. Group [+ or -] was further identified as G. fusca according to the morphology of the reproductive foramen. We conclude that the use of ITS2 and the availability of universal primers provide an ideal DNA barcode for molecular identification of acaroid mites. The use of multiple target genetic markers in conjunction with morphological approaches will improve the accuracy of Acaridida identification. Key words: acaroid mites, taxonomy, universal primers, molecular identification, DNA barcode. L'identification moleculaire des acariens est difficile en raison de la faible disponibilite de donnees moleculaires dans GenBank. Dans ce travail, des acariens echantillonnes dans la poussiere de farine a Xi'an en Chine ont ete classifies/groupes de maniere preliminaire sur la base de leur morphologie. Des amorces universelles ont ensuite ete produites pour amplifier et examiner differents codes-barres a ADN pour identifier ces acariens. Soixante echantillons ont ete classifies en six groupes sur la base de leur morphologie. Les groupes 1 et 2 comprenaient des echantillons appartenant au Dermatophagoides farinae et au Tyrophagus putrescentiae, tandis que les echantillons des groupes 3 a [+ or -] n'ont pas ete identifies au niveau de l'espece. L'ITS2 a montre une plus grande efficacite dans l'identification moleculaire que les sequences COI, 12S et 16S. Les groupes 1-6 ont ete identifies comme etant composes respectivement de D. farinae, T. putrescentiea, Suidasia nesbitti, Chrotoglyphus arcuatus, Lepidoglyphus destructor et Goheria sp. Les resultats d'une analyse phylogenetique etaient conformes a la classification morphologique. Le groupe [+ or -] a ensuite ete identifie comme etant compose du G. fusca sur la base de la morphologie du foramen reproducteur. Les auteurs concluent que l'utilisation de l'ITS2 et la disponibilite d'amorces universelles fournissent un code-barre ideal pour l'identification moleculaire des acariens. Le recours a plusieurs marqueurs genetiques, en conjonction avec les approches morphologiques, permettront d'ameliorer l'exactitude de l'identification des Acaridides. [Traduit par la Redaction] Mots-cles : acariens, taxonomie, amorces universelles, identification moleculaire, code-barre a ADN., Introduction Acaroid mites, belonging to the suborder Acaridida and the order Acariformes, are a large group of harmful mites that are prevalent in the human living environment where they pose [...]

Whether ribosomal genes can be used as DNA barcodes for molecular identification of Demodex (Acariformes: Demodicidae) is unclear. To examine this, Demodex folliculorum, D. brevis, D. canis, and D. caprae were collected for DNA extraction, rDNA fragments amplification, sequencing, and analysis. The V2 and V4 regions of SSU rDNA; D5, D6, and D8 regions of LSU rDNA; and ITS region were obtained from the four morphospecies. BLAST analysis showed that the obtained sequences matched those of Demodex or Aplonobia (Acariformes: Tetranychidae) in Raphignathae. Phylogenetic trees derived from V2, V4, D5, D6, and D8 regions, but not from ITS region, showed that the four species of Demodex clustered independently. Sequence divergence analysis further demonstrated that D5, D6, and D8 regions had obvious barcoding gap between intraspecific and interspecific divergences, with the gap of D5 (16.91%) larger than that of D6 (11.82%) and D8 (4.66%). The V2 and V4 regions did not have a barcoding gap, as the intraspecific and interspecific divergences partially overlapped. For the ITS region, intraspecific and interspecific divergences completely overlapped. These results suggest that the D5, D6, and D8 regions of LSU rDNA, especially D5, are suitable DNA barcodes for Demodex. Key words: Demodex, rDNA fragments, sequence analysis, DNA barcode. Il demeure incertain si les genes ribosomiques peuvent servir de codes a barres de l'ADN pour l'identification moleculaire chez le genre Demodex (Acariformes : Demodicidae). A cette fin, des echantillons de Demodex folliculorum, D. brevis, D. canis et D. caprae ont ete collectes en vue de l'extraction d'ADN, d'amplification de fragments de l'ADNr, de sequencage et d'analyse. Les regions V2 et V4 de l'ADNr de la petite sous-unite, les regions D5, D6 et D8 de l'ADNr de la grande sous-unite, ainsi que l'ITS ont ete obtenues pour les quatre morpho-especes. Des analyses BLAST ont revele que les sequences obtenues correspondaient a celles des genres Demodex ou Aplonobia (Acariformes : Tetranychidae) au sein des Raphignathae. Les arbres phylogenetiques derives des regions V2, V4, D5, D6 et D8, mais non ITS, ont montre que les quatre especes de Demodex formaient des groupes distincts. Une analyse de la divergence des sequences a montre que les regions D5, D6 et D8 presentaient un fosse clair entre les degres de divergence rencontres aux niveaux intra- et interspecifiques, cet ecart etant plus grand chez D5 (a 16,91 %) que chez D6 (11,82 %) et D8 (4,66 %). Les regions V2 et V4 n'ont pas produit de tel fosse du fait que les divergences intra- et interspecifiques se chevauchaient completement. Ces resultats suggerent que les regions D5, D6 et D8 de l'ADNr de la grande sous-unite, particulierement D5, sont aptes a servir de codes a barres chez le genre Demodex. [Traduit par la Redaction] Mots-cles : Demodex, fragments d'ADNr, analyse de sequences, code a barres de l'ADN., Introduction Mites of the genus Demodex are important pathogens that cause demodicidosis, such as rosacea, blepharitis, and acne in humans, laipi disease in dogs, and skin nodules in goats (Hsu [...]

There has been no widely accepted DNA barcode for species identification of Demodex. In this study, we attempted to solve this issue. First, mitochondrial cox1-5′ and 12S gene fragments of Demodex folloculorum, D. brevis, D. canis, and D. caprae were amplified, cloned, and sequenced for the first time; intra/interspecific divergences were computed and phylogenetic trees were reconstructed. Then, divergence frequency distribution plots of those two gene fragments were drawn together with mtDNA cox1-middle region and 16S obtained in previous studies. Finally, their identification efficiency was evaluated by comparing barcoding gap. Results indicated that 12S had the higher identification efficiency. Specifically, for cox1-5′ region of the four Demodex species, intraspecific divergences were less than 2.0%, and interspecific divergences were 21.1-31.0%; for 12S, intraspecific divergences were less than 1.4%, and interspecific divergences were 20.8-26.9%. The phylogenetic trees demonstrated that the four Demodex species clustered separately, and divergence frequency distribution plot showed that the largest intraspecific divergence of 12S (1.4%) was less than cox1-5′ region (2.0%), cox1-middle region (3.1%), and 16S (2.8%). The barcoding gap of 12S was 19.4%, larger than cox1-5′ region (19.1%), cox1-middle region (11.3%), and 16S (13.0%); the interspecific divergence span of 12S was 6.2%, smaller than cox1-5′ region (10.0%), cox1-middle region (14.1%), and 16S (11.4%). Moreover, 12S has a moderate length (517 bp) for sequencing at once. Therefore, we proposed mtDNA 12S was more suitable than cox1 and 16S to be a DNA barcode for classification and identification of Demodex at lower category level. [ABSTRACT FROM AUTHOR]