Naked dragonfishes Gymnodraco acuticeps and G. victori (Bathydraconidae, Notothenioidei) off Terre Adélie are a single species
Taxonomists have generally considered the two bathydraconid species Gymnodraco acuticeps Boulenger, 1902 and Gymnodraco victori Hureau, 1963 as synonymous based on field experience or from personal communications. However, no study has been devoted to that question and here we address it using three lines of evidence: comparison of variable DNA sequences, morphology and cytogenetics. We sequenced four molecular markers for a large sampling to test the delimitation between the two species from individuals caught off Terre Adélie (type locality of G. victori); among them is the cytochrome oxidase I (COI) gene, for which a large reference database is available in the Barcode of Life project for many taxa. However it contains only two Gymnodraco acuticeps sequences and none from G. victori. The karyotype of G. victori was obtained and compared with the one from G. acuticeps. From specimens from the MNHN collections, we recorded the two external characters most commonly used in the field to assign individuals to these species. The maximum divergence recorded in the COI sequences between two Gymnodraco specimens is 0.005% (K2P,) or 0.03% (p-distance), and there are no distinct clusters separating the two morphological entities with any of the four markers: all sequences were identical or nearly identical. No difference was found between the karyotypes of the two species. When a large number of specimens are studied, the pattern of the anterior canine teeth of the lower jaw and the other most visible external features used to distinguish the species by Hureau (1963) are actually more variable than originally described. We place G. victori and G. acuticeps into synonymy, the former being a junior synonym of G. acuticeps.