Morphology and DNA Barcoding highlights the presence of a cryptic skate species in the Southwest Atlantic Ocean

GABBANELLI, V.; CONCHA, F. J.; VAZQUEZ, D. M.; GONZÁLEZ CASTRO, M; DÍAZ DE ASTARLOA J. M.; MABRAGAÑA E.

Conferencia; Sharks International Conference; 2018

The yellownose skate, Zearaja chilensis, is a largeskate that has been reported from the coasts ofChile in the Southeastern Paci c to Southern Brazilin the Southwestern Atlantic. Due to its geographicalrange, biological traits, and levels of exploitation,this species was listed as vulnerable by the IUCN.Recent molecular studies have called into questionthe conspeci city between specimens from theseopposite coasts of South America, which can haveimplications for the conservation status of the species. e aim of this study is to verify the identityof specimens identi ed as Z. chilensis in Argentinawith respect to specimens from Chile. A total of 50specimens from Argentinean waters (AW) and 22from Chilean waters (CHW) were examined in orderto compare their external morphology, spinulationpattern, clasper, and egg capsules. Tissue samples(AW=12, CHW=2) were obtained and sequence datafor the Cytochrome Oxidase Subunit I (COI) genewere generated. Additionally, public sequenceswere obtained from BOLD (AW=25, CHW=8).Despite its external similarity, several traits wereconsistently different between specimens fromboth regions. Adults from AW presented longerpreorbital length and shorter distance between rstgill openings than those from CHW. AW specimenspresented 3-5 rows of caudal thorns, whereas mostspecimens from CHW had only one row. Dermaldenticles were restricted to the rostral area in AWskates, whereas in CHW skates most of the dorsalsurface of the disc was covered with denticles, witha smooth area in the centre of pectoral ns. Majordi erences in clasper morphology were also found.For instance: in AW specimens, terminal bridge (tb)is straight towards tip of dorsal terminal 2 cartilage(dt2) and sentinel (st) does not reach tb, whereasin CHW specimens tb is curved towards tip of dt2and st reach tb; ventral terminal cartilage of CHWhas a longer apophysis and the outer edge is widerthan those from AW. Egg capsules of AW skateshad wider lateral keels than these of their Chileancounterparts. Molecular analysis revealed two wellde ned cohesive clusters, corresponding to AW andCHW specimens, respectively. Average K2P distancebetween groups was 3.4%, a value substantiallyhigher than expected for intraspeci c di erences.Indeed, BINs analysis (algorithm that clusters barcodesequences into OTUs) assigned the sequencesto di erent BINs. ese integrative results stronglysupport that specimens from Argentinean watersknown as Z. chilensis correspond to a di erent nominalspecies than those from Chilean waters.