The mitochondrial genome of the Japanese skeleton shrimp Caprella mutica (Amphipoda: Caprellidea) reveals a unique gene order and shared apomorphic translocations with Gammaridea

Abstract

This study presents the complete mitochondrial (mt) genome of the amphipod Caprella mutica, an east-Asian species, which recently invaded the coastal regions of North America, Europe, and New Zealand. It is the first complete sequence of a member of the amphipod subclade Caprellidea. The mt genome has a total length of 15,427 bp and is organized in a circular double-strand molecule. All 37 mt genes are present, including the common set of 22 tRNAs. Particularly noticeable is the duplication of the control region (CR). The additional CR is located between nad6 and cob, and is almost identical to the original one. The most extensive changes in the gene order affect nad5 and a block consisting of trnH, nad4, nad4L, and trnP—all inserted near the original CR. The gene nad5 is also inverted. Furthermore, a comparison with the pancrustacean ground pattern reveals additional changes of individual tRNA genes. Some of these changes are also shared by Metacrangonyx longipes and Parhyale hawaiensis. These arrangements were found only in amphipods and might be considered as apomorphic by character states of Amphipoda. In all the three species, there is good evidence that trnG originated from a rare duplication/remolding event of the adjacent trnW gene. Nevertheless, each of the three available amphipod mitogenome sequences also bears unique rearrangements. C. mutica, however, shows the most extensive rearrangement in comparison with the pancrustacean ground pattern.

Keywords::

• Caprella mutica
• Amphipoda
• mitochondrial genome
• gene rearrangements
• phylogeny
• control region duplication

Acknowledgments

The authors wish to thank Prof. Thomas Bartolomaeus for his support all phases of this study at the FU Berlin as well as at the University of Bonn. The authors are grateful to Prof. Heinz-Dieter Franke (Biologische Anstalt Helgoland) and Dr Achim Meyer (Univ. Mainz) for sending specimens of C. mutica. They also thank Maria Orland (University of Bonn) for technical assistance in the molecular laboratory. FK did the laboratory work and wrote the manuscript. LP supervised the research and edited the manuscript.

Declaration of interest: This study was supported by a NaFöG Berlin grant to FK and by a German science foundation (DFG) grant (Po 765/2-1,2) to LP. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.