Giant Pacific octopus

## Description

The giant Pacific octopus (Enteroctopus dofleini, formerly also Octopus apollyon ), also known as the 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, Japan, and Korean Peninsula. 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 the largest octopus species, based on a scientific record of a 71-kg (156-lb) individual weighed live.

## Appearance

E. dofleini is distinguished from other species by its large 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) American zoologist G.H. Parker found that the largest suckers on a giant Pacific octopus are about 6.4 cm (2.5 in) and can support 16 kg (35 lb) each. The alternative contender for the largest species of octopus 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, including a report of one up to 272 kg (600 lb) in weight with a 9-m (30-ft) arm span. 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 (9.8 ft).

## Diet

E. dofleini preys upon shrimp, crabs, scallop, abalone, cockles, snails, clams, lobsters, fish, squid, and other octopuses. Food is procured with its suckers and then bitten using its tough beak of chitin. It has also been observed to catch spiny dogfish (Squalus acanthias ) up to 1.2 m (4 ft) in length while in captivity. Additionally, consumed carcasses of this same shark species have been found in giant Pacific octopus middens in the wild, providing strong evidence of these octopuses preying on small sharks in their natural habitat. In May 2012, amateur photographer Ginger Morneau was widely reported to have photographed a wild giant Pacific octopus attacking and drowning a seagull, demonstrating that this species is not above eating any available source of food within its size range, even birds.

## Reproduction

The giant Pacific octopus is considered to be long-lived compared to other species, with lifespans typically 3–5 years in the wild. Many other octopuses go through a complete life cycle in one year, from egg to end of life. To make up for its relatively short lifespan, the octopus is extremely prolific. It can lay between 120,000 and 400,000 eggs which are coated in chorion, and attached to a hard surface by the female. The spawn is intensively cared for exclusively by the female, who continuously blows water over it and grooms it to remove algae and other growths. While she fulfills her duty of parental care the female stays close to her spawn, never leaving to feed, leading to her death soon after the young have hatched. The female's death is the result of starvation, as she subsists on her own body fats during this period of approximately 6 months. Hatchlings are about the size of a grain of rice, and very few survive to adulthood. Their growth rate is quite rapid: starting from 0.03 g and growing to 20–40 kg (44–88 lb) at adulthood, which is an increase of around 0.9% per day. Because they are cool-blooded, they are able to use most of their consumed energy for body mass, respiration, physical activity, and reproduction.

During reproduction, the male octopus deposits a spermatophore (or sperm packet) more than 1 m long using his hectocotylus (specialized arm) in the female's mantle. Large spermatophores are characteristic of octopuses in this genus. The female stores the spermatophore in her spermatheca until she is ready to fertilize her eggs. One female at the Seattle Aquarium was observed to retain a spermatophore for seven months before laying fertilized eggs.

Unlike males, only the female giant Pacific octopuses are semelparous, meaning they only breed a single time in their life. After reproduction, they enter a stage called senescence, which involves obvious changes in behavior and appearance, including a reduced appetite, retraction of skin around the eyes giving them a more pronounced appearance, increased activity in uncoordinated patterns, and white lesions all over the body. While the duration of this stage is variable, it typically lasts about one to two months. Death is typically attributed to starvation, as the females have stopped hunting in order to protect their eggs; males often spend more time in the open, making them more likely to be preyed upon.

Increased seawater temperatures also increase metabolic processes. The warmer the water, the faster octopus eggs develop and hatch. After hatching, the paralarvae swim to the surface to join other plankton, where they are often preyed upon by birds, fish, and other plankton feeders. Quicker hatching time may also affect critical timing for food availability. One study found that higher water temperatures accelerated all aspects of reproduction and even shortened lifespan by up to 20%. Other studies concur that warming climate scenarios should result in higher embryo and paralarvae mortalities.

## Population

### Conservation

Giant Pacific octopuses are not currently under the protection of Convention on International Trade in Endangered Species of Wild Fauna and Flora or evaluated in the IUCN Red List. The giant Pacific octopus has not been assessed by the Monterey Bay Aquarium Seafood Watch, although other octopus species are listed. Combined with lack of assessment and mislabeling, tracking the species's abundance is nearly impossible. Scientists have relied on catch numbers to estimate stock abundance, but the animals are solitary and difficult to find. DNA techniques have assisted in genetic and phylogenetic analysis of the species' evolutionary past. Following its DNA analysis, the giant Pacific octopus may actually prove to be three subspecies (one in Japan, another in Alaska, and a third in Puget Sound).

In Puget Sound, the Washington Fish and Wildlife Commission adopted rules for protecting the harvest of giant Pacific octopuses at seven sites, after a legal harvest caused a public outcry. Populations in Puget Sound are not considered threatened.

Regardless of these data gaps in abundance estimates, future climate change scenarios may affect these organisms in different ways. Climate change is complex, with predicted biotic and abiotic changes to multiple processes including oxygen limitation, reproduction, ocean acidification, toxins, effects on other trophic levels, and RNA editing.

## References

https://animalia.bio/giant-pacific-octopus