Identification of octopus species and genetic structure of Octopus insularis in the western Atlantic

The identification of octopus species, particularly those in the genera Octopus and Pinnoctopus, has been challenging due to the species' morphological plasticity and the presence of cryptic species in the western Atlantic. The use of molecular tools like DNA barcoding is important for accurate taxonomic identification, especially in understudied regions like the Greater Caribbean. This study aimed to identify octopus species in the Mexican Caribbean and the southwestern Gulf of Mexico, and to evaluate the genetic structure of Octopus insularis using the mitochondrial COI gene. Here, the species Octopus insularis was recorded for the first time at Banco Chinchorro and Punta Herrero, Quintana Roo, Mexico. Similarly, both O. insularis and Pinnoctopus furvus were recorded for the first time in the Lobos-Tuxpan Reef System. Additionally, 93 new octopus DNA sequences were obtained for the study area. The genetic analysis revealed 31 haplotypes of O. insularis, with a haplotype diversity of 0.53, indicating moderate genetic diversity. Three genetically distinct populations were identified from Brazil to the Gulf of Mexico, with two populations in Brazil showing the highest pairwise Fst values, indicating significant genetic differentiation. Importantly, the study assessed the genetic structure of O. insularis in the Caribbean Sea and Gulf of Mexico for the first time, revealing that these sites form a population. This suggests that the octopus populations in the region, covering areas like Colombia, Panama, Mexican Caribbean (Quintana Roo), and the Gulf of Mexico (Veracruz Reef System and Lobos-Tuxpan Reef System), could be managed as a fishery stock, highlighting the need for a unified approach to the sustainable management of these fishery resources.