Review of the ecological aspects of sympatric species Octopus americanus and Octopus insularis (Cephalopoda: Octopodidae) in the Western Atlantic.

Due to similarities in morphology and overlapping distribution, Octopus americanus and O. insularis (both formerly designated as O. vulgaris) are now considered to be cryptic species inhabiting the western Atlantic, while O. vulgaris inhabits the eastern Atlantic and Mediterranean. The historical lack of distinction made between O. americanus and O. insularis in the scientific literature and fisheries statistics, and persisting confusion regarding the identity and basic biological traits of each species, has hindered proper management of octopus fisheries in the western Atlantic. We attempt to rectify this by identifying the habitat preferences (environmental and biological) of each species from published literature. To this purpose, we compiled 134 studies about O. americanus, O. insularis, and "O. vulgaris" from the western Atlantic and re-identified the species based on the geographic area of occurrence, size, and weight of mature individuals, and visually identifiable morphological and body pattern characteristics. Analysis revealed that O. americanus occurs in temperate waters (15-28 °C), from 0 to 200 m on rocky shores, as well as on sand or shell beds. By contrast, O. insularis occurs from 0 to 50 m in tropical waters with a mean temperature of 23-32 °C, mainly in rocky areas and on coral reefs, and generally targets a greater diversity of prey. The results show that these two species inhabit distinct habitats, which can aid in species identification and in the determination of priority areas for their conservation.