The complete mitochondrial genome and phylogenetic analysis of hydrozoan jellyfish <i>Eirene ceylonensis</i> (Cnidaria, Hydrozoa, Eirenidae) in the coastal sea of Qinhuangdao, China

<i>Eirene ceylonensis,</i> a hydrozoan jellyfish species with a complex polymorphic life cycle, is widely distributed in the Chinese coastal sea. In this study, we conducted sequencing and analysis of the first complete mitochondrial genome of <i>E. ceylonensis,</i> obtained from the coastal sea of Qinhuangdao, China. The linear mitochondrial genome is 14,997 bp in length with the overall AT content being 72.8%, encoding 13 protein-coding genes (PCGs), two transfer RNA (tRNA) genes (<i>tRNA-Met</i> and <i>tRNA-Trp</i>) and two ribosomal RNA (rRNA) genes (<i>rrnS</i> and <i>rrnL</i>). Phylogenetic analysis of 13 PCGs suggests that the <i>E. ceylonensis</i> is closely related to <i>Laomedea flexuosa</i>. The availability of the complete mitochondrial genome of <i>E. ceylonensis</i> will be useful for studying the evolutionary relationships of hydrozoan jellyfish species.