Geometric morphometrics of the scutum for differentiation of trombiculid mites within the genus Walchia (Acariformes: Prostigmata: Trombiculidae), a probable vector of scrub typhus.

摘要: The vectors of scrub typhus are the larval stage trombiculid mites, termed "chiggers". These very small - larvae approximately 0.2 mm in size and therefore their morphological identification is difficult. Trombiculid mites widely distributed across Asia they can be identified at genus level by shape, setae/sensilla distribution dorsal chitin plate (scutum = shield), while species requires more mite characteristics. We recently developed a methodology to ascertain paired matched genotype morphotype individual chiggers, based on autofluorescence brightfield microscopy with subsequent molecular using COI gene (approximately 640bp length). However, 20 chigger specimens characterised genotypic data consisting four [Walchia ewingi 2 subspecies]: Walchia lupella (n = 9), W. (n = 2), alpestris kritochaeta (n = 5) minuscuta (n = 2) we found evidence genetic polymorphism plasticity within Walchia. phylogenetic inference intra-genus relationships spp., (Blankaartia spp. served as outgroup), delineated five included an average interspecific divergence mean distance 0.218 (0.126 0.323). applied landmark-based outline-based geometric morphometric (GM) approaches differentiate scutum measurements. A total 261 images were examined GM (140 specimens) (121 techniques. All showed significant differences shape. smallest both largest was analysis, respectively. shapes clearly distinguished from other species. Cross-validated classification scores different depending digitizing techniques better than GM. conclude that morphologically closely-related further differentiated features alone, approaches. This technique promising tool for much-needed characterization studies chiggers needs evaluation genotyping genera trombiculids.