Giant Pacific Octopus

***Enteroctopus dofleini***, also known as the **giant Pacific octopus** or **North Pacific giant octopus**, is a large marine cephalopod belonging to the genus *Enteroctopus*. Its spatial distribution includes the coastal North Pacific, along California, Oregon, Washington, British Columbia, Alaska, Russia, northern Japan, and Korea. It can be found from the intertidal zone down to 2,000 m (6,600 ft), and is best adapted to cold, oxygen-rich water. It is arguably the largest octopus species, based on a scientific record of a 71-kg (156-lb) individual weighed live. The alternative contender is the seven-arm octopus (*Haliphron atlanticus*) based on a 61-kg (134-lb) incomplete carcass estimated to have a live mass of 75 kg (165 lb). However, a number of questionable size records would suggest *E. dofleini* is the largest of all octopus species by a considerable margin.

## Description

All cephalopods have bilateral symmetry, a shell gland, a mantle, and a well-developed head with sucker-covered arms. The octopus has eight arms, each of which has two rows of suckers. Many of the suckers are lined with papillae or hooks for adhesion. The web between the arms can be expanded to form a parachute-like structure to capture prey. In the center of the arms is a mouth, containing beak and radula (toothed-tongue).

Schematic lateral aspect of octopod features

Cephalopods have a paralytic and digestive toxin in two salivary glands to aid in opening prey. Water is pulled into the mantle and over gills or lamellae for oxygen uptake, and can be ejected forcefully through the siphon for jet propulsion. They are able to reach speeds up to 40 km/h (25 mph) for short sprints. They tend to use their arms as legs, and slowly crawl along the bottom. The siphon is also used to expel ink for escaping predators. The entire body of the octopus is compressible, so they are able to fit through any opening slightly bigger than the size of their beaks (the only hard part of their bodies). Their arms are muscular hydrostats, which lengthen, contract, and contort. Octopuses are poikilothermic or cool-blooded, and have three hearts and blue, copper-based blood.

The mantle of the octopus is spherical in shape and contains most of the animal's major organs. By contracting or expanding tiny pigment-containing sacs within cells known as chromatophores, an octopus can change the color of its skin, giving it the ability to blend into the environment. Subcategories of chromatophores include iridophores (reflective platelets) and leucophores (refractive platelets). Octopuses are also able to alter their skin texture, providing even better camouflage. Dermal muscles in the octopus's skin can create a heavily textured look through papillation, or cause skin to appear smooth. All of these abilities are under nervous system control.

*E. dofleini* is distinguished from other species by its sheer size. Adults usually weigh around 15 kg (33 lb), with an arm span up to 4.3 m (14 ft). The larger individuals have been measured at 50 kg (110 lb) and have a radial span of 6 m (20 ft). However, highly questionable records of specimens up to 272 kg (600 lb) in weight with a 9-m (30-ft) arm span have been reported. *Guinness World Records* lists the biggest as 136 kg (300 lb) with an arm span of 9.8 m (32 ft). A UN catalog of octopuses sizes *E. dofleini* at 180 kg (396 lb) with an arm length of 3 m. American zoologist G.H. Parker found that the largest suckers on a GPO are about 6.4 cm (2.5 in) and can support 16 kg (35 lb) each.

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