Abstract

The Squalus genus is divided into three taxonomic categories that comprise various species, although their nomenclature is frequently inconsistent across different ichthyologists and taxonomies. In the South western Atlantic Ocean, there are three known species of spiny sharks, S. acanthias, S. cubensis, and S. mitsukurii, with discrepant classifications. During campaigns conducted by the INIDEP Chondrichthyan Fisheries Program, 27 Squalus specimens from the Argentine-Uruguayan Common Fishing Zone (ZCPAU) and Argentine coast were collected and morphologically identified onboard. We then coupled DNA COI Barcode technology with BLASTn and BOLD IDS tools to molecularly validate those taxonomic classifications. COI gene sequences were generated for those 27 specimens and compared to available reference sequences (FISHBOL database) from S. acanthias, S. cubensis, S. mitsukurii, S. suckleyi, S. blainville, and S. megalops from different oceanic regions. Genetic distances (K2P) and phylogenetic relationships (via neighbor-joining phylogenetic tree and Median-joining haplotype network) were also estimated for the COI data. A total of thirteen samples identified by the BOLD Identification System did not match the Squalus species identified using morphological evidence. Our analyses also indicated that S. mitsukurii, S. acanthias, and S. cubensis are three clearly distinct species, while S. lobularis is deemed equivalent to S. mitsukurii (K2P=0.35%). Our haplotype network also confirmed the existence of S. acanthias, S. cubensis, and S. mitsukurii in the studied area. The application of these molecular techniques and analyses have proved effective at accurately identifying Squalus species; hence we recommend their use to validate former morphology-based taxonomic identifications

Keywords

squalidae, sharks, COI, south western atlantic, barcode