The mitochondrial genomes of five spring and groundwater amphipods of the family Crangonyctidae (Crustacea: Amphipoda) from eastern North America

We sequenced the mitochondrial genomes of one spring-dwelling (Crangonyx forbesi) and four groundwater amphipods (Bactrurus brachycaudus, Stygobromus allegheniensis, S. pizzinii, and S. t. potomacus) from eastern North America using a shotgun sequencing approach on an Illumina HiSeq 4000 (Illumina, San Diego, CA). All five mitochondrial genomes encoded 13 protein-coding genes, 22 transfer RNAs (tRNAs), and two ribosomal RNAs (rRNAs) representative of subphylum Crustacea. Although the four groundwater species exhibited gene orders nearly identical to the ancestral pancrustacean gene order, the spring-dwelling species, C. forbesi, possessed a transposition of the trnH–nad4–nad4l loci downstream after nad6–cytb–trnS2. Moreover, a long nad5 locus, longer rrnL, and rrnS loci, and unconventional start codons distinguished C. forbesi from the four groundwater amphipods. Overall, our five amphipod mitogenomes add to the increasing publicly available mitogenome resources for amphipods that are not only valuable for studying the evolutionary relationships of this diverse group of crustaceans but for exploring the evolution of mitochondrial genomes in general.