Common octopus

Cryptic species remain poorly studied in octopuses. Following the reinstatement of the cryptic species, Octopus americanus, suggestions that it should supplant two taxa, Octopus vulgaris types I & II, in the western central and southwestern Atlantic Ocean, respectively, had yet been investigated in southeast Florida. To delineate this species, an integrative approach including morphological assessments and phylogenetic analyses of mitochondrial (16S & COI) and nuclear (rhodopsin) genes was employed. The utility of swabbing as a minimally invasive alternative DNA sampling method to tissue was also investigated. This taxon displays similar morphological traits to O. americanus. Maximum Likelihood phylogenetic inference placed this taxon in a highly supported monophyletic group with O. americanus. Both sampling methods delineated this taxon, though tissue was more successful. These results indicate that southeast Florida’s O. vulgaris-like species represents O. americanus. Thorough species delineation approaches advance our understanding of biodiversity, evolution, and ecology, and inform management practices.

Octopus predation and species selection contribute to community structure in benthic habitats, where plastic pollution accumulates. This study investigated how the bioactive plastic additive oleamide alters trophic interactions and behaviors of the common octopus (Octopus vulgaris) and its prey. We quantified activity budgets and trophic interactions for octopuses and multiple prey types (hermit crabs, free-living crabs, bivalves, and gastropods) before and after exposure to oleamide. Our analysis suggested that some taxa (octopuses and hermit crabs) exhibit more active behaviors during oleamide exposure. Free living crabs responded primarily to the threat of octopus predation, while other taxa did not show clear behavioral responses. Exposure to oleamide increased trophic interactions and the probability of mobile prey taxa being observed on the same side of the aquarium as the octopus, thus increasing the opportunity for predation. Our results support previous research showing that plastic leachates can impair decision-making, making prey more susceptible to predation.