THE COMPLETE MITOCHONDRIAL GENOME OF GRAPSUS ALBOLINEATUS LATREILLE AND COMPARATIVE ANALYSIS OF GRAPSOIDEA

For a long time, the phylogeny of Grapsoidea (Decapoda: Brachyura) has been controversial. Complete mitochondrial genome (mitogenome) provides important information for better understanding of gene rearrangement, molecular evolution and phylogenetic analysis. However, only a few mitogenomes of Grapsidae species have been reported and the phylogenetic status of Grapsidae within Grapsoidea remains unresolved. In order clarify the phylogenetic relationship of Grapsoidea and further explore the correlation between phygeny and mitogenome rearangement, the complete mitogenome of Grapsus albolineatus, the representative species of Grapsidae was sequenced. The total length of this mitogenome is 15577 bp, containing 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and a control region. The nucleotide composition is shown as follows: 33.4% A, 12.0% G, 20.6% C, 34.0% T, respectively, with a high AT bias (67.4%). Majority protein-coding genes are initiated by the typical start codon ATN, with an exception GTG in ATP8 and ND1, most of them terminate with TAN, while two genes (COⅡ and Cyt b) use a single T as a stop codon. Leu (15.8%) and Cys (0.81%) are the most and least frequently used amino acid, respectively. Except fortRNA-Ser1, which lacks DHU arm, all tRNAs have the typical cloverleaf structure. The phylogenetic relationships among Grapsoidea were reconstructed based on nucleotide sequences of 13 PCGs using maximum likelihood (ML) and Bayesian (BI) methods. The phylogenetic trees obtained identical topological structures, which showed that all grapsid crabs clustered into a clade, and G. albolineatus shared the closest relationship with G. tenuicrustatus. Sesarmidae and Xenograpsidae clustered together, and then formed a sister group with Gecarcinidae, and finally form a sister group with Grapsidae. Varunidae formed a separate clade. A significant correlation between gene rearrangement and phylogeny was found in Grapsoidea for the first time. These findings will contribute to a better understanding of gene rearrangement and molecular evolution, as well as provide insights into the phylogenetic studies of Grapsoidea.