Abstract
With six valid species, Luciobrotula is a small genus of the family Ophidiidae, commonly known as cusk-eels. They are benthopelagic fishes occurring at depths ranging from 115–2300 m in the Atlantic, Indian, and Pacific Oceans. Among them, Luciobrotula bartschi is the only known species in the West Pacific. Three specimens of Luciobrotula were collected from the Philippine Sea, Bismarck Sea, and Solomon Sea in the West Pacific during the AURORA, PAPUA NIUGINI, and MADEEP expeditions under the Tropical Deep-Sea Benthos program, and all of them were initially identified as L. bartschi. Subsequent examination with integrative taxonomy indicates that they belong to two distinct species, with the specimen collected from the Solomon Sea representing a new species, which is described here. In terms of morphology, Luciobrotula polylepis sp. nov. differs from its congeners by having a relatively longer lateral line (end of the lateral line below the 33rd dorsal-fin ray) and fewer vertebrae (abdominal vertebrae 13, total vertebrae 50). In the inferred COI gene tree, the two western Pacific species of Luciobrotula do not form a monophyletic group. The genetic K2P distance between the two species is 13.8% on average at the COI locus.
Highlights
Luciobrotula Smith & Radcliffe, 1913, a rare deep-sea fish genus, is currently classified in the subfamily Neobythitinae (Ophidiidae)
Advanced species delimitation analyses with Automatic Barcode Gap Discovery (ABGD) and based Poisson Tree Processes (bPTP) based on the same c oxidase subunit I (COI) dataset reveal a congruent result with a prediction of three Operational taxonomic units (OTUs), corroborating the phylogenetic finding (Fig. 2)
L. polylepis sp. nov., is grouped together with L. brasiliensis in having a lower precaudal vertebrae count. Another group with a higher precaudal vertebrae count consists of L. bartschi, L. coheni, L. corethromycter, L. lineata, and L. nolfi
Summary
Luciobrotula Smith & Radcliffe, 1913, a rare deep-sea fish genus, is currently classified in the subfamily Neobythitinae (Ophidiidae). All of them are benthic dwellers and can usually be found in the tropical deep waters of continental slopes worldwide (Cohen 1974; Nielsen 2009) They are probably carnivorous, though only a single study mentioned a partially digested caridean shrimp found in the gut of L. corethromycter (Cohen 1964). L. bartschi has the widest distribution in the IndoWest Pacific, ranging from the Gulf of Aden and South Africa, east to the Hawaiian Islands, and north to Japan It is the only species previously known from the West Pacific (Nielsen 2009)
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