Octopus americanus:a cryptic species of theO. vulgarisspecies complex redescribed from the Caribbean

The common octopusOctopus vulgarisCuvier, 1797, once considered a cosmopolitan species, is a species complex composed by six species:O. tetricus,O. cftetricusandO. sinensisin the Pacific; type I and II, in the West Atlantic; and type III in the Indian Ocean around South Africa. The tropical western central Atlantic is an important octopus fishing ground targetingO. maya,O. insularis, and a cryptic species considered to beO. vulgaristype I. In order to clarify the identification of this octopod, phylogenetic analyses were carried out with mitochondrial (COI and 16S) and nuclear (rhodopsin) genes, together with morphological analyses of 16 specimens caught in the northeastern continental shelf of Yucatan (Mexico). The main morphological traits differing fromO.vulgariswere the presence, position and size of enlarged suckers and hectocotylus sucker number in males. Genetic distances and haplotype networks of the species complex were estimated using 285 COI sequences of nineOctopusspecies from 14 different locations around the world. The octopod sequences from Yucatan clustered within a monophyletic group that included sequences ofO. vulgaristype II for the three genes analyzed. Phylogenetic distances with other members of the complex ranged between 2.71 and 3.89% using COI data. These genetic results support the presence ofOctopus americanusMonfort, 1802 (formerly known asO. vulgaristype II) along the Yucatan continental shelf, a new octopod extending from the north of Argentina to the northwest coast of the USA.