Today is World Octopus Day and we're excited to celebrate the 289 species of eight-armed cephalopods who roam the seas—from the minuscule to the gargantuan. Octopuses are incredible animals with even more incredible anatomy and physiological functions.
Here are the 7 things you need to know about one of the most alien-like creatures on planet Earth.
Octopuses are masters at contorting their bodies. Have you ever heard that an octopus can get past any opening they can fit their break through? It's true—just look at the guy in this video. The massive octopus easily fits through the tiny opening on the side of a boat, much to the astonishment (and denial) of one of the people on board.
Octopuses look alien on their exterior, but what about inside? Turns out, their innards are equally as strange. For instance, octopuses have three hearts: two serve the function of pumping blood to their gills while the third one pumps blood everywhere else. And speaking of blood, these guys have blue blood due to hemocyanin, a copper-based protein.
Octopuses have incredibly powerful arms and suckers which they use to grab and stick to things. Using a ring called an infundibulum, they create an insanely tight seal that produces that suctioned grip. These rings get used so frequently that the skin on them falls off every few weeks, similar to how snakes shed their skin.
When threatened, octopuses shoot ink in order to confuse their predators. But what makes up the ink and why is it dangerous? Octopus ink is comprised of mucus and melanin, which according to National Geographic, contains the enzyme tyrosinase, that can "impair sight, taste, and smell," or get stuck in a predator's gills causing death by suffocation. In fact, an octopus' ink can even kill the octopus if it inhales the ink for the same reason.
Perhaps the thing octopuses are most well-known for is their ability to camouflage themselves when hunting and when they're being hunted. In this clip, Heidi the octopus can be seen rapidly changing color—a feat made possible by cells that contain pigment called chromatophores.
Octopuses have the ability to change at will so that they can hide in plain sight. What's even wilder is that a lot of octopuses also have the ability to imitate textures by controlling the shape of the papillae on their skin in addition to colors, making them the ultimate masters of disguise.
Octopuses come in vastly different sizes. The smallest known octopus is the Wolfi, shown in the clip. Live Science reports that this little guy is "smaller than an inch long and weighs less than a gram." This is a huge contrast to the world's largest known eight-arrmed cephalopod: the Giant Pacific Octopus. This massive octopus can weigh anywhere between 22 and 110 pounds and has a longer lifespan than any other species of octopus.
Octopuses exhibit problem solving skills that set them apart from other animals, thanks to their nine—yes, nine—brains. Octopuses have a brain located in the anterior portion of their mantles in addition to the brains that independently operate each arm. This is also why these creatures are so dextrous; imagine having a brain controlling your arms and legs individually.
According to London's Natural History Museum, "the common octopus (Octopus vulgaris) has around 500 million [neurons]," similar to a dog's brain.