Analyses of the overlength control region in Metacarcinus magister (Decapoda: Brachyura) and phylogenetic study of Menippidae species

The complete mitochondrial genomes (mitogenomes) can provide important information for molecular evolution and phylogenetic relationships of marine invertebrates, especially in Brachyura. Menippidae species are representative of typical marine crabs, but only two Menippidae species mitogenomes were sequenced previously, and the phylogenetic relationships of the class Menippidae (Decapoda: Brachyura: Eriphioidea) remain to be resolved. In this research, the mitogenomic characteristics of Metacarcinus magister (Eriphioidea: Menippidae) has been newly studied. The length of M. magister was 48,820 bp, which contained the typical 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. We did a series of analyses surrounding the characteristics of Metacarcinus magister CR. Phylogenetic analysis, life circumstances and selective pressures were all tried to explain the formation of this length, which was emerged approximately three times compared with the normal length of Brachyuran mitogenomes. Phylogenetic analyses based on the dataset of 132 Decapodan mitogenomes indicated that all the Menippidae crabs clustered together as a group. In the clade, M. magister was related to all the other four Menippidae species, such as Pseudocarcinus gigas and Myomenippe fornasinii . Moreover, the rearrangement mechanism of these four species has been predicted to provide stronger evidence for phylogenetic analysis. In general, the results obtained in this study will contribute to a better understanding of the cause of the unusual length of M. magister , and provide new insights into the phylogeny of Brachyura.