Studies on Molecular Taxonomy and Morphological Characteristics of Haematobia irritans exigua (de Meijere, 1903); A New Range Extension in the Bargur Hills of Erode District in Tamil Nadu, India

The flies of the genus Haematobia (Diptera:Muscidae) are hematophagous ectoparasites of medical and veterinary importance. The morphological identification of these flies is often complicated due to their similarities. This was the first documentation of Haematobia irritans exigua in Tamil Nadu which affected free-ranging Bargur Cattle (Bos indicus) from Bargur Hills of Tamil Nadu. The aim of this research was to provide the details on the molecular characterization and molecular divergence of the cytochrome c oxidase subunit 1 gene (COI) and 28S Ribosomal RNA of Haematobia irritans exigua and to compare them with the morphological features. The results of this study showed that the nucleotide composition of the COI gene of Haematobia irritans exigua had a higher AT (69.5%) and a lower GC (30.4%). The rate of transition was higher than that of transversion. The intra-specific distance based on COI gene analysis did not exceed 1.1%, while the inter-specific distance between different species ranged from 0.9% to 14.1%. A neighbor-joining tree and an Unweighted Pair Group Method with Arithmetic Mean (UPGMA) tree were constructed using 1000 bootstrapped samples to analyze the phylogenetic relationship between different muscidae species based on the COI gene as an identification marker. The analysis of 28S Ribosomal RNA showed an intra-specific distance of 1.6% and an inter-specific distance ranging from 1.49% to 8.56%. The 28S rRNA revealed the presence of intra-specific variation among the species. Additionally, this study found notable color variations on the thorax of the flies in the same population, along with a minute phenotypical variation with minimum intraspecific distance among the flies in the same population. This taxonomic data of the hematophagous fly Haematobia irritans exigua would be well-intentioned for identification.