An octopus holds hands with a diver. Is this Cthulhu preaching?

Octopus is a general term for more than 300 species of mollusks under the order Octopoda of the class Cephalopoda. Their body structure looks simple, with an oval body that includes all the internal organs, and eight "long legs", each with 1-2 rows of suction cups. Their body is soft and has no bones, except for the keratin jaws for eating that are hard.

Although they may not seem to have high intelligence, they are actually the smartest invertebrates in the world. They are good at camouflage and hiding, spraying ink for cover, getting out of mazes, escaping from aquariums, opening bottle caps to get food, and even managing small cross-species teams for hunting. These survival skills are all impressive.

The largest octopus in the world

The Pacific octopus, Enteroctopus dofleini, whose official Chinese name is water octopus, is classified as an Enteroctopus of the Octopoda order. There are 6 species of octopus in this genus, each of which is a huge monster with a diameter of more than 3 meters when its arms are spread out. The arms of the Pacific octopus can reach a diameter of 6 meters and a weight of 75 kilograms, making it the largest octopus in the world. The smallest octopus, Octopus wolfi, is only 2.5 centimeters in length, which may not be as big as a suction cup on the legs of a Pacific octopus.

The Pacific octopus is widely distributed in the cold temperate coastal areas of the northern Pacific Ocean where the water temperature is lower, from the southern coast of California in the United States to the coasts of Alaska and Japan, so it is also called the North Pacific giant octopus; its habitat range is wide, from the intertidal zone to the deep sea of ​​2,000 meters; its blood rich in hemocyanin can help the Pacific octopus better obtain oxygen in an environment with lower water temperatures, helping them stay energetic.

Pacific octopus at the Monterey Bay Aquarium | Bill Abbott / Wikimedia Commons

Pacific octopuses particularly like to live in relatively secluded environments such as large kelp forests. Although they are active all day long, they usually hide in rock caves with multiple holes and constantly look for more comfortable bases with more food. They are most active in the second half of the night, and most of their moves and hunting occur in the second half of the night. Every time they go out, they remember the way home based on the terrain. Studies have found that Pacific octopuses have a large range of activities, with a range of activities of up to 50,000 square meters in 20 days and a moving distance of up to 4.8 kilometers.

Gentle and shy big guy

The giant Pacific octopus is often described as a demon in novels and movies, but in fact they are very shy and gentle big guys, spending more than 90% of the day fixing and hiding themselves. Similar to many other octopuses, the Pacific octopus has a powerful camouflage system. Relying on the pigment cells, skin folds and powerful nervous system of the epidermis, it can change the color and texture of its skin, blending in with the environment and hiding in the environment.

Imaginary image of a person being attacked by an octopus, from Monsters of the Sea: Legendary and Authentic | Wikimedia Commons

There have been reports of Pacific octopuses attacking divers and snatching their equipment, but these are accidental. The suction cups on the octopus's eight "long legs" have unique chemical receptors to search and distinguish the smell of prey. Octopuses need to rely on their arms and legs to feel around to sense prey or determine whether a moving object is prey. Of course, if you smell like their prey, you may be bitten, don't ask me how I know.

The Pacific octopus has a wide range of food sources. As long as the size and taste are suitable, it will basically not refuse small sharks, crabs, shellfish, and even seabirds. When hunting, the Pacific octopus will use its strong suction arms to hold the prey and bring it back to the cave to enjoy. It likes to place the leftovers at the entrance of the cave.

Apart from humans, large Pacific octopuses have almost no natural enemies in the wild. Every year, more than 30,000 tons of Pacific octopuses are caught for food and as bait in longline fisheries.

Octopus burger | Arnaud 25 / Wikimedia Commons

Waiting for new life

Pacific octopuses are solitary creatures that only come into contact with the opposite sex when they are adults and reproduce. In autumn, Pacific octopuses migrate from the deep sea to the nearshore and mate in the water layer about 100 meters deep. The male uses a stem-like arm (hectocotylus) of the arm to transport sperm to the female's oviduct. After mating, the male returns to the deep water area and dies a few months later, while the female continues to migrate to the shallow water area, and the sperm is stored in the female's oviduct gland. After mating, the female will eat a lot to store energy.

Stem-shaped arms of Argonauta bottgeri, from Cephalopoda of the Hawaiian Islands | Wikimedia Commons

After a few months of mating, the ovaries will mature. The female Pacific octopus will find a reef cave in shallow waters about 50 meters away, clean the reef, and lay rice-sized fertilized eggs on the reef in the form of "grape bunches". Then the female octopus will stop eating during the next 6-7 months of egg-laying, and will always guard these eggs, drive away predators that try to steal the eggs, and move and clean these hatching fertilized eggs to bring them oxygen to increase the hatching rate. Soon after the fertilized eggs hatch, the mission has been accomplished and the female Pacific octopus will die.

Newly hatched Pacific octopuses are only 1 cm in size and will float on the sea surface for the next few months. After 1-3 months, they return to the seabed and begin benthic life. Each female Pacific octopus lays 100,000 to hundreds of thousands of eggs, and only a few can grow up to adulthood and complete the alternation of new and old lives.