Complete Mitogenome of Cruznema tripartitum Confirms Highly Conserved Gene Arrangement within Family Rhabditidae

Mitochondrial genomes have widely been used as molecular markers in understanding the patterns and processes of nematode evolution. The species in genus Cruznema are free-living bacterivores as well as parasites of crickets and mollusks. The complete mitochondrial genome of C. tripartitum was determined through high-throughput sequencing as the first sequenced representative of the genus Cruznema. The genome is comprised of 14,067 bp nucleotides, and includes 12 protein-coding, two rRNA, and 22 tRNA genes. Phylogenetic analyses based on amino acid data support C. tripartitum as a sister to the clade containing Caenorhabditis elegans and Oscheius chongmingensis. The analysis of gene arrangement suggested that C. tripartitum shares the same gene order with O. chongmingensis, Litoditis marina, Diplocapter coronatus, genus Caenorhabditis, and Pristionchus pacificus. Thus, the mitochondrial gene arrangement is highly conserved in the family Rhabditidae as well as some species in Diplogasteridae.