Utility of Mitochondrial and Ribosomal Genes for Differentiation and Phylogenesis of Species of Gastrointestinal Bot Flies

Abstract

Larvae of Gasterophilus spp. (Diptera: Oestridae) cause gastrointestinal myiasis of equids. However, their identification may be problematic due to morphological similarities between species infesting identical regions of the digestive tract. In this study, genes encoding for mitochondrial cytochrome oxidase I (COI) and for the 16S and 28S ribosomal subunits of the most commonly encountered Gasterophilinae subfamily species [i.e., Gasterophilus haemorrhoidalis (L.), Gasterophilus inermis (Brauer), Gasterophilus intestinalis (De Geer), Gasterophilus nasalis (L.), and Gasterophilus pecorum (F.)] were studied, together with Gyrostigma pavesii (Corti), a rhinoceros parasite, and Hypoderma lineatum (De Villers), as outgroup taxa. Analysis identified interspecific differences that allowed their unequivocal identification. The high genetic homology among the sequences of G. haemorrhoidalis and G. intestinalis (i.e., 100, 99.86, and 99.46% in the 28S, COI, and 16S genes, respectively) strongly support the hypothesis that they are morphotypes of the same species. Phylogenetic analyses (maximum-likelihood and parsimony) were performed using PAUP; all analyses supported monophyly of subfamily Gasterophilinae. This study confirms the utility of the COI and 16S and 28S rRNA genes to address diagnostic and phylogenetic questions in Gasterophilus species.

Taxonomic review of Gasterophilus (Oestridae, Gasterophilinae) of the world, with updated nomenclature, keys, biological notes, and distributions

“…They have adapted to a larval life in the alimentary tract of Equidae (Zumpt 1965; Grunin 1969; Colwell et al 2006), and their presence can lead to serious injuries or even death of the host (Hall and Wall 1995; Sequeira et al 2001; Colwell et al 2006; Bezdekova et al 2007; Getachew et al 2012). Because of their great veterinary importance, Gasterophilus species have received considerable attention since the early 1800s (Clark 1815; Dove 1918; Patton 1937; Zumpt and Paterson 1953; James 1974; Otranto et al 2005a, b; Colwell et al 2006, 2007; Zhang et al 2016; Liu et al 2016; Huang et al 2017; Li et al 2018). A total of more than 40 species-group names have been proposed for what is here recognized as nine valid species because of extensive intraspecific variation (Zumpt 1965; Grunin 1969; Pont 1980; Soós and Minář 1986; Cogley 1991a), and a series of misidentifications can be ascribed to their similar larval morphology (Colwell et al 2007; Li et al 2018).…”