New Records and Mitochondrial DNA Markers of Two Deep-sea eels Collected from the Western Pacific Ocean

Abstract Two deep-sea eels collected from the western Pacific Ocean are described in this study. Based on their morphological characteristics, the two deep-sea eel specimens were assumed to belong to the cusk-eel family Ophidiidae and the cutthroat eel family Synaphobranchidae. To accurately identify the species of the deep-sea eel specimens, we sequenced the mitochondrial genes (cytochrome c oxidase subunit 1 (CO1) and 16S ribosomal RNA (16S rRNA)). Through molecular phylogenetic analysis based on mtDNA CO1 and 16S rRNA gene sequences, these species clustered with the genera Bassozetus and Synaphobranchus, suggesting that the deep-sea eel specimens collected are two species from the genera Bassozetus and Synaphobranchus in the western Pacific Ocean, respectively. This is the first study to report new records of the genera Bassozetus and Synaphobranchus from the western Pacific Ocean based on mitochondrial DNA markers.