First genetic validation and diagnosis of the short-finned squid species of the genus <Emphasis Type="Italic">Illex</Emphasis> (Cephalopoda: Ommastrephidae)

Squids of the genus Illex are representative of the family Ommastrephidae and account for 65% of the world’s cephalopod captures. Illex is formed by four taxa distributed throughout the Atlantic Ocean (I. argentinus, I. coindetii, I. illecebrosus and I. oxygonius), whose identification and phylogenetic relationships based on morphological characters remain controversial. Thirty-seven enzyme-coding loci were analysed in 230 individuals from seven populations of Illex and ten specimens of Todaropsis eblanae, which were used as the outgroup. Two to four enzyme loci (ALPDH*, IDHP-1*, MEP* and SOD*) were diagnostic among Illex species depending on the species-pair comparison. Individuals morphologically identified as I. oxygonius were also found genetically distinct, which proves the taxonomic validity of this species. No significant intraspecific genetic heterogeneity was detected within Illex argentinus, I. coindetii and I. illecebrosus (Mean G _ST= 0.011, 0.003, 0.017, respectively). I. illecebrosus and I. oxygonius were shown as sister species with a close relationship to I. argentinus, whereas I. coindetii formed a different lineage.