Taxonomic status of deep-sea sharks Deania calceus and D. hystricosa (Centrophoridae)

The taxonomic status and identification of the deep-sea sharks of the genus Deania have been controversial mainly due to morphological similarities between some of its species. The aim of this work was to update the taxonomic status of Deania hystricosa (and other putative species, such as D. calceus and D. profundorum) and the validity as a true taxa using specimens from the Atlantic (East-Central and Southeast) and the North Atlantic (Cantabrian Sea) as determined by analysis of sequences of COI and 16 S rRNA genes and comparative analysis of meristics of skin on different body parts. Traditionally, individuals of the genus Deania, including D. hystricosa, D. quadrispinosa, D. calceus and D. profundorum, were classified according to the length of the denticle crown. In our study, this character was found to be significantly dependent on the sexual maturity stage or length of the individual and the area of the body where the denticles were taken. Here, 23 individuals of these species were caught during campaigns carried out in the Atlantic Ocean (East-Central and Southeast) and in the North Atlantic (Cantabrian Sea), in order to be analysed for the mitochondrial genes 16 S ribosomal RNA (16 S rRNA) and cytochrome oxidase subunit I (COI). Phylogenetic analysis of concatenated sequences showed two clearly differentiated groups: one consisting of the species D. profundorum, and the other one consisting of the species belonging to D. calceus and D. hystricosa. The genetic differences measured between D. profundorum group and calceus-hystricosa group (3.9%) were within the range of congeneric species, whereas those differences obtained between D. calceus and D. hystricosa (0.2%) were within the range of intraspecific variation of any of the 3 species analyzed. These results suggest that D. calceus and D. hystricosa are synonyms.

Automated summary

This study aimed to update the taxonomic status of deep-sea shark genus Deania, especially focusing on D. hystricosa, D. calceus, and D. profundorum. Genetic analysis showed that D. calceus and D. hystricosa are synonyms, with genetic differences within the range of intraspecific variations.