The first mitochondrial genome from Mysida (Crustacea: Malacostraca) reveals an unusual gene arrangement.

This is the first report to present the Neomysis orientalis mitochondrial genome as a representative from the order Mysida. While mitochondrial protein-coding genes (PCGs) commonly use several alternatives to ATN as start codons, all 13 PCGs in N. orientalis mitochondrial genome initiate with ATG or ATA. Five PCGs (atp6. atp8. cob. nad4 and nad4L) start with ATG, while the other genes (cox1-3. nad1-3. nad5 and nad6) start with ATA. Only two PCGs (cox2 and nad2) in the N. orientalis mitochondrial genome end with incomplete stop codons (T- or TA-), and all the remaining ones have TAA or TAG stop codon. Only one PCG (nad4L) is encoded on the light strand and all other 12 PCGs are located at the heavy strand. Both rRNAs (srRNA and lrRNA) are encoded on the light strand. In common with 15 of the other 18 mitochondrial genomes from Peracarida, the major gene arrangement in the N. orientalis mitochondrial genome is different from the pancrustacean ground pattern. The largest conserved gene block in N. orientalis only contains two genes but those in the other 18 peracarid mitochondrial genomes contain more than five genes. Thus, the N. orientalis mitochondrial genome, as the first mitochondrial genome from the order Mysida, reveals an unusual gene arrangement that is unique compared with the other malacostracan mitochondrial genomes.