DNA barcodes identify medically important tick species in Canada.

Medically important ticks (Acari: Ixodidae) are often difficult to identify morphologically. A standardized, molecular approach using a 658 base pair DNA barcode sequence (from the 5' region of the mitochondrial cytochrome c oxidase subunit I gene) was evaluated for its effectiveness in discriminating ticks in North America, with an emphasis on Canadian ticks. DNA barcodes were generated for 96 of 154 specimens representing 26 ixodid species. A genetic cluster analysis was performed on the barcode sequences, which separated specimens into haplogroups closely corresponding with morphologically identified species. The tree topology was further supported by a BIN analysis. COI sequences generated were found to have a mean maximum intraspecific divergence of 1.59% and a mean nearest neighbour divergence of 12.8%, indicating a significant "barcode gap". This study also revealed possible cryptic diversity among specimens morphologically identified as Ixodes soricis and Ixodes texanus. A PCR-based test for Borrelia burgdorferi determined that 18.1% of Lyme-competent ticks in this study were positive. This study is also the first to record a B. burgdorferi-positive exoskeleton. In conclusion, DNA barcoding is a powerful tool that clinicians can use to determine the identification of tick specimens which can help them to suggest whether an attached tick is a potential health risk.

Dimethyldimethyl Hydantoin: An Alternative Fluid for Morphological and Genetic Preservation.

Modern taxonomy requires the preservation of biospecimens for both morphological and molecular applications. The utility of a previously identified preservative, dimethyldimethylhydantoin hydantoin (Dekafald®), to retain both physical diagnostic traits and the DNA integrity of biological specimens remains unknown. Using 439 eggs and 414 larvae from two North American fish species, we compared three hydantoin solutions at different concentrations (5%, 10%, and 20%) with gold standard preservatives (10% buffered formalin, 95% ethanol) to evaluate morphological trait retention up to 90 days, and DNA barcoding success up to 56 days. While the 5% hydantoin solution had the most sequencing success by 56 days, the 10% hydantoin solution was the best multipurpose preservative. Future work should assess the performance of ∼10% hydantoin solution over longer time periods, and its applicability to other taxa such as Arthropoda.