Characterization of the fragmented mitogenome of the European badger louse Trichodectes melis reveals conserved organization in non-coding regions

Abstract Mitochondrial genome fragmentation is widespread in lice but remains poorly understood, with molecular data still scarce for many ectoparasitic species, particularly those associated with wild hosts. Here, we characterize the complete mitochondrial genome of Trichodectes melis , a chewing louse parasitizing the European badger ( Meles meles ). By combining Illumina® sequencing with PCR amplification, followed by cloning and Sanger sequencing, we assembled and annotated the fragmented mitogenome of T. melis , which comprises 13 circular minichromosomes. Together, these molecules encode the canonical set of 37 mitochondrial genes (13 protein-coding genes, 22 transfer RNAs and 2 ribosomal RNAs). Gene content and organization are highly conserved relative to Trichodectes canis , although differences were observed among other Trichodectidae species. The high A + T content observed in both coding and non-coding regions is consistent with that of related species, except in the genus Bovicola , which exhibits comparatively lower values. Notably, the non-coding regions of the minichromosomes displayed substantial intra-individual heteroplasmy in both length and nucleotide composition. Despite this variability, these regions exhibited a conserved structural architecture comprising 3 conserved sequence blocks, microsatellite motifs and tandem repeats, suggesting an important functional role in mitochondrial replication and transcription. Phylogenetic analyses based on concatenated protein-coding genes and cox1 sequences recovered T. melis as the sister species of T. canis and supported the monophyly of the genus Trichodectes . These findings provide the first mitogenomic characterization of T. melis and contribute to a better understanding of mitochondrial genome evolution in insects with fragmented mitogenomes.