The First Complete Mitochondrial Genome of Bdelloidea (trombidiformes, Eupodina) and Comparative Genomics Provide Insights into Gene Rearrangement and Evolution of Trombidiform Mites

In this study, we reported the first complete mitogenome of Bdelloidea, Spinibdella lignicola, and combined with other 26 trombidiform mitogenomes, we conducted gene order (GO) comparative analyses of trombidiform mites. The mitogenome of S. lignicola, having a full set of 37 coding genes, exhibits a novel gene cluster of ???trnA-trnQ-trnS1-trnR??? among trombidiform mites. Phylogenetic reconstruction revealed that S. lignicola is closely related to Riccardoella reaumuri, supporting its position within Eupodides. Like most previous studies, the monophyly of Trombidiformes is rejected for Eriophyoidea separates from Trombidiformes. Shared gene blocks and derived gene boundary analysis concluded that four blocks (cox1~cox3; nad6~trnS2; nad1-trnL2; trnM ~ trnC) are the dominant arrangements of trombidiform mite mitogenomes and evolution synapomorphies occurred in trombidiform mites have phylogenetic relatedness. Furthermore, we propose possible ancestral GO of Trombidiformes and provide GO evidence for eriophyoid mites evolving independently from non-eriophyoid trombidiform mites. Our study confirms that comparative analysis of GO is a valuable information tool that improves our understanding of mitogenome evolution and phylogeny of trombidiform mites.