A New Species of the Eel Genus Gnathophis (Congridae, Anguilliformes) from the Seamounts of the Emperor–Hawaiian Chain, Western and Central North Pacific

Gnathophis johnsoni sp. nov. is described on the basis of 15 specimens (138–380 mm TL) from the Emperor–Hawaiian Seamount Chain in the western and central North Pacific. The new species is most similar in morphology to G. bathytopos (Atlantic), G. cinctus (eastern Pacific), and G. smithi (Nazca and Salas-y-Gomez Seamounts in the southeastern Pacific) by the sensory pore configuration and vertebral count, but differs from these species in the following characters in combination: darkly pigmented pectoral fin, dorsal fin with black margin broadened caudally and extended onto the distal half of the caudal fin, relatively long head, jaws, gill slit and caudal fin, and on average a greater preanal distance. Although most of morphometrics overlap between the new species and its closest relatives, multivariate statistical analyses clearly discriminate this species. Molecular analysis shows sister relationships between the new species and G. cinctus, with 1.81% of genetic divergence, which significantly exceeds the differences between the haplotypes belonging to the same species (0.36 and 1.08% of divergence, usually not exceeding 0.9%) and confirms both species as close but distinct. The close relationship of G. johnsoni sp. nov. and G. cinctus represents a rare case of biogeographical relations between western and eastern Pacific demersal fish faunas. Molecular data suggest that some morphologically similar species may represent independently evolved lineages, though the group of Gnathophis possessing elevated lateral-line pores is likely monophyletic.