A new species of the genus Dysommina (Teleostei: Anguilliformes: Synaphobranchidae: Ilyophinae) from the Western Pacific.

Dysommina orientalis, a new species of Ilyophine eel from off Taiwan and Japan is described and illustrated. The species had long been recognized as Dysommina rugosa in the western Pacific and is distinguished from D. rugosa by a lower number of predorsal vertebrae, a higher number of total vertebrae, shorter head length, smaller eye size, reduced vomerine dentition, and an increased number of both mandibular and maxillary teeth, as well as significant differences in DNA sequence in COI and 16S.

Deep-ocean origin of the freshwater eels.

Of more than 800 species of eels of the order Anguilliformes, only freshwater eels (genus Anguilla with 16 species plus three subspecies) spend most of their lives in freshwater during their catadromous life cycle. Nevertheless, because their spawning areas are located offshore in the open ocean, they migrate back to their specific breeding places in the ocean, often located thousands of kilometres away. The evolutionary origin of such enigmatic behaviour, however, remains elusive because of the uncertain phylogenetic position of freshwater eels within the principally marine anguilliforms.