[4][5][6] E. dofleini play an important role in maintaining the health and biodiversity of deep sea ecosystems, cognitive research, and the fishing industry.

The giant Pacific octopus was first described in 1910 by Gerhard Wülker of Leipzig University in Über Japanische Cephalopoden.

[7] The specific name dofleini was chosen by Gerhard Wülker in honor of German scientist Franz Theodor Doflein.

[3] 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.

[14][15] E. dofleini preys on shrimp, crabs, scallops, abalones, cockles, snails, clams, lobsters, fish, squid, and other octopuses.

Marine mammals, such as harbor seals, sea otters, and sperm whales depend upon the giant Pacific octopus as a source of food.

In the eastern Pacific waters off the coast of Japan, migration coincides with seasonal temperature changes in the winter and summer.

Dens range across depth and substratum type including caves, holes dug beneath rock, and even trash on the ocean floor such as bottles, tires, pipes, and barrels.

[29] However, over longer periods of time, E. dofleini relocate to new dens situated relatively nearby, within an average distance of 13.2 meters.

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.

[23] During reproduction, the male octopus deposits a spermatophore (or sperm packet) more than 1 m (3.3 ft) long using his hectocotylus (specialized arm) in the female's mantle.

Analysis of egg clutches has shown evidence of polygyny and polyandry in giant Pacific octopuses, where males and females mate with multiple partners.

Changes in sensitivity to touch are attributed to decreasing cellular density in nerve and epithelial cells as the nervous system degrades.

[42] 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.

[44] Giant Pacific octopuses are commonly kept on display at aquariums due to their size and interesting physiology, and have demonstrated the ability to recognize humans with whom they frequently come in contact.

These responses include jetting water, changing body texture, and other behaviors that are consistently demonstrated to specific individuals.

[23] The octopus brain has folded lobes (a distinct characteristic of complexity) and visual and tactile memory centers.

[47] 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.

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).

[citation needed] Regardless of these data gaps in abundance estimates, future climate change scenarios may affect these organisms in different ways.

Using tag and recapture methods, scientists found they move from den to den in response to decreased food availability, change in water quality, increase in predation, or increased population density (or decreased available habitat/den space)[52] Because their blue blood is copper-based (hemocyanin) and not an efficient oxygen carrier, octopuses favor and move toward cooler, oxygen-rich water.

Each fall in Washington's Hood Canal, a habitat for many octopuses, phytoplankton and macroalgae die and create a dead zone.

Warming seawater temperatures promote phytoplankton growth, and annual dead zones have been found to be increasing in size.

[56] The burning of fossil fuels, deforestation, industrialization, and other land-use changes cause increased carbon dioxide levels in the atmosphere.

[citation needed] Because octopuses have hemocyanin as copper-based blood, a small change in pH can reduce oxygen-carrying capacity.

[23] Researchers have found high concentrations of heavy metals and PCBs in tissues and digestive glands, which may have come from these octopus' preferred prey, the red rock crab (Cancer productus).

[3] What effects these toxins have on octopuses are unknown, but other exposed animals have been known to show liver damage, changes in immune systems, and death.