Two Complete Mitochondrial Genomes of Potamanthidae (Ephemeroptera): Genome Features and Phylogenetic Implications

The family Potamanthidae is widely distributed across the Holarctic and Oriental regions, with nymphs often utilized as bioindicators for water pollution and human-induced environmental disturbances. However, limited mitochondrial genomes (mitogenomes) have been reported for this family. This study presents the first complete mitochondrial genome sequences of two Potamanthidae species, Potamanthus longitibius and Rhoenanthus youi. The mitogenome sizes were 15,430 bp and 15,232 bp, with A + T contents of 68.79% and 66.75%, respectively. The most abundant amino acids were phenylalanine (Phe), isoleucine (Ile), glycine (Gly), and alanine (Ala), with leucine (Leu2) showing the highest relative synonymous codon usage (RSCU) value. The analysis of tRNA secondary structures revealed high conservation among the tRNAs encoded on the H-strand. Phylogenetic reconstruction, incorporating 40 species from 13 families of Ephemeroptera, confirmed the monophyly of all the families and supported a sister group relationship between Potamanthidae and Ephemeridae. Additionally, the sequence previously identified as Rhoenanthus sp. JZ-2021 was reassigned to the genus Potamanthus. This study provides valuable insights into the evolutionary relationships within Potamanthidae and lays a foundation for future phylogenetic and taxonomic research.