Octopuses (or octopi, if you prefer) are cephalopods, invertebrates that also include squid and cuttlefish. They have bulbous heads, large eyes, and eight very useful arms. “Cephalopod” is Greek for “head-foot,” which makes sense, since their limbs are attached directly to their head.
Octopuses are highly intelligent animals, masters of camouflage that have evolved an array of tricks over tens of millions of years to avoid or thwart would-be attackers. They can match the colors and even textures of their surroundings, allowing them to hide in plain sight. If a predator gets too close octopuses can escape quickly, shooting themselves forward by expelling water from a muscular tube called a siphon. Octopuses can also release a cloud of black ink, which obscures them and dulls an encroacher’s sense of smell.
Their soft bodies mean octopuses can fit into impossibly small nooks and crannies, as long as the holes are not smaller than the only hard parts of their bodies: their beaks. If all else fails, octopuses can lose an arm to an attacker and regrow one later.
The octopus’s arms are lined with hundreds of suckers, each of which can be moved independently thanks to a complex bundle of neurons that acts as a brain, letting the animal touch, smell, and manipulate objects. Octopuses can open clamshells, maneuver rocks—even dismantle the filtration systems of an aquarium tank. They’ve also can develop opinions about people; one routinely squirted water down the back of a keeper it seemed to dislike. Another shot a jet of water at a light to cause a commotion.
Habitat and behavior
There are around 300 species of octopus and they are found in every ocean. Most live on the seafloor, but some, like the paper nautilus, drift nearer to the surface. Octopuses mostly feed on crabs, shrimp, and mollusks.
Solitary animals, they typically live alone, sometimes in dens they build from rocks, sometimes in shells they pull over on top of themselves. Some even make a door for themselves—a rock pulled into place once they’re safely tucked into their homes.