Geometric morphometrics to distinguish the cryptic species Anopheles minimus and An. harrisoni in malaria hot spot villages, western Thailand.

Anopheles minimus Theobald 1901 and An. harrisoni Harbach & Manguin 2007 belong to the same species complex. They are morphologically similar and can exist in sympatry but have blood host preferences. The most accurate method for their identification is based on molecular techniques. Here, we measure the level of interspecific discrimination by geometric morphometry. Sixty-seven An. minimus and 22 An. harrisoni specimens were selected based on their morphological integrity and confirmed by identification polymerase chain reaction of internal transcribed spacer 2. These samples were used as reference data allowing for a morphometric identification based on geometric shape. Despite size overlap between the two species, there was a significant shape divergence allowing for differentiation of An. minimus and An. harrisoni with 90% accuracy. An intraspecific study of An. minimus showed a summer period associated to the reducing of wing size, which did not influence the shape-based differentiation of An. harrisoni. Wing venation geometry can be used to distinguish between these cryptic species mainly based on shaped divergence. This study suggests that geometric morphometrics represent a convenient low-cost method to complement morphological identification, especially concerning damaged specimens, i.e., insects having accidentally lost the anatomical features allowing a reliable morphological identification.

Species-specific primers for the detection of lymphatic filariasis vectors: Mansonia bonneae and Mansonia dives.

Lymphatic filariasis remains a public health problem in some areas of Thailand and Southeast Asia. The nocturnally subperiodic and periodic form of brugian filariasis is transmitted by the Mansonia species. It is difficult to distinguish especially wild caught specimens between certain species due to morphological similarities. In the present study, species-specific primers were designed for amplification of cytochrome oxidase subunit I (COI) markers to simplify the identification of two morphologically similar species: Ma. bonneae and Ma. dives by PCR detection method. The primer specificity was checked against associated Mansonia species as well as other species of mosquitoes. It was found that the developed species-specific primer sets have proved to be effective for reliable identifying the two morphologically similar species of Mansonia. We therefore recommend to use these primer sets as a tool for epidemiological investigations on lymphatic filariasis.