Frontiers in Marine Science (Nov 2015)
DNA Barcoding and Genetic Structure Analysis of Deep-Sea Notacanthiform Fishes
Abstract
Notacanthiformes Goodrich, 1909 is an order of deep-sea, benthopelagic or benthic fishes distributed from the continental slope to the abyssal plain, at a depth of between 125 and 4,900 m, but mostly occurring at depths of 450-2,500 m. They are characterized by an eel-like body, a snout projecting conspicuously beyond the mouth, large connective tissue nodules inserted between the pterygoid arch and maxilla and pelvic fin webs joined in the ventral midline. Fishes from this order were classified applying DNA barcoding. Cytochrome c oxidase subunit I (COI) sequences belonging to new North Atlantic specimens and already deposited BOLD public records were used. The specimens from the two families of the order, Halosauridae (halosaurs) and Notacanthidae (spiny eels), formed separated monophyletic clades in neighbor-joining trees and the sequences clustered as coherent species. Nine out of 16 species of Halosauridae and 9 out of 10 species of Notacanthidae were represented including 166 sequences of which 96% were successfully identified. The DNA barcode of the rare species Lipogenys gillii was obtained for the first time ever. The DNA barcode was further tested by exploring the genetic structure and historical demography of four species of notacanthiforms from five sample locations of the North Atlantic and South West Pacific. Neutrality tests, mismatch distribution and haplotype networks analyses pointed to a past bottleneck episode followed by a fast demographic expansion for all the samples. The genetic structure of the abyssal halosaur Halosauropsis macrochir showed no significant differences between the North Atlantic and South West Pacific samples. DNA barcoding was successful in validating field identifications and assigning species names to sequences of notacanthiforms worldwide. These results constitute a first example of high connectivity and gene flow in this group of deep-sea fish species. The historical demography suggests population variations that may be due to past glaciation events.
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