Complete Mitochondrial Genomes of Two Species of the Genus Loricaria (Loricariidae: Loricariinae) and Its Phylogenetic Implications

Loricaria, the type genus of the armored catfish family Loricariidae, is a species-depauperate lineage in the subfamily Loricariinae, with only 18 valid species formally recognized to date. However, the extremely high morphological homogeneity across congeners of this genus has long posed great obstacles to accurate taxonomic delimitation when relying solely on phenotypic traits. In this study, we newly sequenced and fully annotated the complete mitochondrial genomes (mitogenomes) of L. parnahybae and L. simillima. The two assembled mitogenomes are 16,581 bp and 16,371 bp in length respectively, both carrying the conserved vertebrate mitochondrial gene set consisting of 37 functional units (22 transfer RNA genes, 13 protein-coding genes (PCGs), 2 ribosomal RNA genes) and 1 non-coding control region. Among Protein Control Genes, only the Cox1 gene uses GTG as the start codon, whereas the remaining 12 PCGs initiate with ATG. The observed stop codons include TAA, as well as the incomplete stop codons TA and T. We reconstructed phylogenetic trees using both maximum likelihood and Bayesian inference methods, based on a dataset covering mitogenome sequences of 22 Loricariidae species and 2 outgroup taxa. Phylogenetic analyses consistently supported the monophyly of Loricariinae, Hypostominae, and Hypoptopomatinae. These results clarify the evolutionary position of L. simillima and L. parnahybae within Loricariidae and will contribute to elucidating the complex phylogenetic relationships among Loricariidae species.