East Pacific red octopus

Octopus rubescens (Commonly the East Pacific red octopus, also known as the ruby octopus, a preferred common name due to the abundance of octopus species colloquially known as red octopus) is the most commonly occurring shallow-water octopus on much of the North American West Coast, and a ubiquitous benthic predator in these habitats. Its range extends from the southern Gulf of California at least to the Gulf of Alaska, but may also occur in the western Pacific Ocean. "O. rubescens" occurs intertidally to a depth of 300 m.
Taxonomy.
In the years prior to the description of this species in 1953, "O. rubescens" was widely considered to be a young "Enteroctopus dofleini". Many early descriptions were based on a combination of "O. rubescens" and "E. dofleini". To date, the taxonomy of this species remains somewhat unresolved. S.S. Berry’s 1953 description is in truth a brief diagnosis, and considering the exceptionally wide range of the species, the animals currently covered under "O. rubescens" may prove to represent several subspecies or a species complex.
Size and description.
"O. rubescens" generally grows to a mantle length of 8–10 cm (3.1 - 3.9 in), and arm length of 30–40 cm (11.8 - 15.7 in). Adult weight is generally 100–150 grams (3.5 - 5.3 Oz), but animals up to 400 grams (14.1 Oz) in weight have occasionally been observed.
Like all octopuses, "O. rubescens" can change its color and texture, making its appearance highly variable. Color can vary from a deep brick red, to brown, to white, or mottled mixtures of the three. It can be easily confused with small individuals of "Enteroctopus dofleini" in the northern end of this species' range. The two can be differentiated by the presence of three eyelash-like papillae below the eyes of "O. rubescens" that are absent in "E. dofleini".
Intelligence.
Like most octopuses, "O. rubescens" is thought to be among the most intelligent of invertebrates. The presence of individual personalities is a hallmark of intelligence, and "O. rubescens" was the first invertebrate in which individual personalities were demonstrated.
Diet and foraging behavior.
"O. rubescens" is a generalist predator and has been maintained on a wide variety of gastropods, bivalves, crabs and barnacles in the lab. So far, very little quantification of its diet in the wild has been made. The two studies on the subject determined diets in Puget Sound, Washington to be dominated by gastropods, particularly "Nucella lamellosa" and "Olivella baetica", but also composed of clams, scallops and crabs. The planktonic larvae of "O. rubescens" have also been observed in the wild to consume krill.
As part of its feeding behavior, "O. rubescens" will pounce on prey and display a stereotypical sequence of color changes at the moment of capture. Following the capture of bivalve prey, it will often drill a hole through the shell to deliver venom and more easily open the shell. The octopuses will often concentrate their drill holes near the adductor muscles of the bivalve prey.
A recent study has suggested "O. rubescens" may choose prey based on fat digestibility rather than on the amount of calories the octopuses is able to obtain from the food items. If this is true, the authors further argue, this would make "O. rubescens" a specialist predator by some measures, rather than a generalist, due to it specific nutrient requirements.