1. an octopus can regenerate a lost tentacle, and octopuses with missing limbs are fairly common in nature.
2. two-thirds of an octopus’ nervous system is found its arms. this gives the arms a lot of local control, allowing a detached arm to continue to crawl, suction, and for the chromatophores to change color.
3. octopuses have a relatively short life expectancy. some species live for as little as six months, while larger species may live for up to five years under suitable circumstances.
4. most octopuses can eject a thick blackish ink in a large cloud to aid in escaping from predators. the main coloring agent of the ink is melanin, which is the same chemical that gives humans their hair and skin color. this ink cloud is thought to dull smell, which is particularly useful for evading predators that are dependent on smell for hunting, such as sharks. ink clouds of some species might serve as pseudomorphs, or decoys that the predator attacks instead.
5. they have three hearts; one that pumps blood throughout the body and two that pump blood to the gills.
6. octopus blood is blue in color because the oxygen-binding protein hemocyanin contains copper. their blood is a poor carrier of oxygen, which helps explain the animal’s sometimes apparent laziness.
7. although the octopus cannot hear, its vision is acute; its large, complex eyes are so advanced that camera manufacturers have used their eyes as a model to improve the camera lens. until recently, because of the curve of a camera’s lens, the picture often blurred at the edges. to correct this, nicer camera models often contained up to eight lenses, which was both bulky and expensive. by copying the structure of an octopus eye, which has several thin layers of multiple densities to bend and focus light, camera manufacturers were able to create a camera lens that can now produce a clear picture— and the camera is smaller and cheaper to produce.
8. receptors on each sucker allow the octopus to taste whatever it touches. each sucker has up to 10,000 neurons.
9. an octopus’ camouflage is aided by specialized skin cells which can change the apparent color, opacity, and reflectiveness of the epidermis. chromatophores contain yellow, orange, red, brown, or black pigments; most species have three of these colors, while some have two or four. this color-changing ability can also be used to communicate with or warn other octopuses. the very venomous blue-ringed octopus becomes bright yellow with blue rings when it is provoked.
10. octopuses are highly intelligent, likely more so than any other order of invertebrates. the exact extent of their intelligence and learning capability is much debated among biologists, but maze and problem-solving experiments have shown that they do have both short- and long-term memory. their short lifespans limit the amount they can ultimately learn.