The complete mitochondrial genome of the stream loach (Schistura sikmaiensis) and its phylogenetic implications

Stream loaches belonging to the genus Schistura are important components of the aquarium trade as well as subsistence fishery in many Southeast Asian countries. Currently, these species are threatened by escalating habitat loss and therefore need instant conservation initiatives. Effective conservation measures, however, require meaningful taxonomic diagnoses of species groups within this genus. To provide an insight into the phylogeny, we sequenced the complete mitogenome of S. sikmaiensis for the first time and further studied its phylogenetic implication within Nemacheilidae. The full-length mtDNA of S. sikmaiensis was 16581 bp long and consisted of 22 transfer RNA (tRNA) genes, 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, and a major non-coding control region. All of the genes were encoded on the H-strand, except for eight tRNAs and ND6 gene. The gene order and composition observed in the mitochondrial genome of S. sikmaiensis corresponds to the presumed teleost ground pattern. Phylogenetic analyses based on 13 PCGs yielded a well-supported topology that confirmed the non-monophyletic state of the genus Schistura. Besides, it also revealed that S. sikmaiensis is genetically closer to S. reticulofasciata compared to other Schistura species. The results presented herein will further promote investigations on molecular taxonomy, genetic diversity, evolution and conservation strategies for Schistura and other Nemacheilidae fishes.