Everybody knows what an octopus looks like, right? Big bulbous head, large eyes, and eight distinctive arms.
And other fascinating octopus facts…
There are around 300 species of octopi. (Also correct plurals are octopuses and octopodes.)
An octopus has blue blood! They have copper in their blood rather than iron like us.
They have three types of specialized skin cells that can quickly change color to blend in with their surroundings.
The largest identified species is the Giant Pacific Octopus, which can weigh up to 50 pounds and have 14-foot-long arms. (They are called arms because they have suckers down the entire length. If the suckers were only on the ends, they would be called tentacles.)
Octopuses collect shells and other objects to build fortresses around their lairs.
Their bodies are almost completely soft, with no internal skeleton. The only hard part is their beak-like jaws. This overall softness allows them to squeeze through narrow slits between underwater rocks, helpful when they are fleeing a predator.
And yes, an octopus has three hearts: one that pumps blood through its body (including its arms), and two that pump blood through its gills, so it can breathe under water.