A new lernaeopodid genus (Copepoda, Siphonostomatoida) parasitizing Macrourus holotrachys (Gadiformes) from deep waters in the southeastern Pacific Ocean, based on molecular and morphological analyses.

A new genus and species of Clavella-like specimens parasitic on Macrourus holotrachys, previously reported as a host for Clavella adunca, clearly differ from the latter in the position and condition of the antennal sympod and rami, which are uniramous in C. adunca but biramous in the new species. Additional morphological traits, such as antennule armature, maxillary size, and the absence of basal swelling on the cephalothorax, support these differences. Molecular analyses corroborate these distinctions. The 28S rDNA sequences of Neoclavella holotrachia gen. nov. et sp. nov. show genetic divergence of 4.1-4.7% and 6.2-6.8% from those of C. adunca and Lernaeopodidae gen. sp., respectively, all of which cluster within a strongly supported clade. Clavellomimus macruri exhibits sequence divergence with Clavellotis girellae (15.3%) and with Clavellotis dilatata (15.5%), although the corresponding nodes in the phylogram are weakly supported. COI mtDNA sequences of Neoclavella holotrachia gen. nov. et sp. nov. grouped together with Clavella spp. in a strongly supported node, with genetic distances ranging from 17.3% to 18.2% between the new genus and the other species. These results suggest that Macrourus holotrachys and possibly other Macrourus species are not hosts for C. adunca, as previously reported. Alternatively, M. holotrachys may be parasitized by both C. adunca and the new species. These findings suggest that some previous records of C. adunca from fishes off Chile may have been misidentified.