Molecular diversity of deep-sea fishes (Actinopterygii: Teleostei) in the western South Atlantic: A high diversity and new findings revealed by DNA barcoding.

The deep sea hosts approximately 15% of all fish species, but the difficulty of sampling limits our knowledge, causing large gaps in geographic distribution, and many deep-sea fish groups still require taxonomic revisions. Herein, the deep-sea fishes collected in the southern Brazil, western South Atlantic, are studied through DNA barcoding resulting in a better understanding of the biodiversity and genetic diversity of the region. The samples were obtained during oceanographic cruises aboard the Brazilian R/V Alpha Crucis, focusing on the continental slope off southern Brazil at depths of 200-1,500 meters. A total of 170 sequences of actinopterygian fishes from 102 different species of 49 families and 19 orders were generated. The DNA barcoding identified 84 sequences at the species level, with the remaining being identified at least to the genus level. A high level of genetic divergence between species was observed, ranging from 3.9% to 36.7%. We provided the first COI sequences for 13 species that, to date, were not represented in databases. Among the species already represented in online databases with COI sequences, we expanded the geographic coverage of existing data. As a result, we increased representation for 16 species in the Atlantic, 26 species in the South Atlantic, and 28 species in the western South Atlantic. Our efforts revealed a diverse deep-sea fish fauna in the region, highlighting new occurrences and demonstrating a high genetic divergence between some taxa.