Complete mitochondrial genome sequence of Nannostomus eques and comparative analysis with Nannostomus beckfordi.

The brown pencilfish, Nannostomus eques is a lebiasinid harvested for ornamental purposes; however, its complete mitochondrial genome sequence is still unknown. To enrich the molecular genetic information pertaining to Nannostomus, we present here the first report of the complete mitochondrial genome sequence of Nannostomus eques and compare it with Nannostomus beckfordi. The total lengths of the N. eques and N. beckfordi mitochondrial genomes were 16,673 bp and 16,742 bp, respectively, and there was a double-stranded ring with a heavy chain and a light chain in the whole structures of both. We used PhyloSuite v1.2.1 to construct the maximum likelihood and Bayesian Analysis trees based on tRNAs, rRNAs, and protein-coding genes (PCGs) data and compared them with other Nannostomus species by referring to other studies. Our study found that N. beckfordi has a closer genetic relationship with N. eques than with Lebiasina astrigata, which belongs to the same family, and we discovered some similarities and even rules in Nannostomus species. Our study provides a molecular basis for the conservation and sustainable use of Nannostomus species.