Comparative Analysis of Complete Mitochondrial Genomes of Five Chromodorididae Species (Nudibranchia:Doridina).

Mitochondrial genome is an important molecular marker for exploring the phylogenetic relationships of species and revealing molecular evolution. In the present study, 5 mitogenomes of Chromodorididae (Chromodoris lochi, Chromodoris colemani, Chromodoris elisabethina, Chromodoris annae and Hypselodoris whitei) were systemically investigated. The lengths of the mitogenomes sequences were 14248 bp, 14257 bp, 14252 bp, 14254 bp and 14856 bp, respectively. Most protein-coding genes (PCGs) were initiated with the common ATG codon and terminated with the TAA and TAG. We calculated Ka/Ks values for all 13 PCGs of Chromodorididae species, all ratios were less than 1, indicating selection by purification. Phylogenetic relationships were constructed by Bayesian inference (BI) and maximum likelihood (ML) methods based on all complete genomes of 50 species, primarily from the family Chromodorididae (Doridina) and 2 outgroups. This phylogenetic tree provided further additional references for the classification of the suborder Doridina. Gene rearrangement suggested a more conserved pattern of gene sequences in the superfamily Chromodoridoidea. These results and newly sequenced will contribute to a better understanding of Chromodorididae and provide reference for further phylogenetic studies.