Octopus can grow back limbs.
There are cannibalistic octupus (for. ex.: Giant Pacific Octopus).
"They are about 90% muscle."
Octopus have blue blood, nine brains, and three hearts.
Use "octopus" when talking about a single octopus or multiple when they are from the same species. Only use "octopi" when talking about different species.
All octopus have venom.
The Alaskan Giant Pacific Octopus can lay more than 90,000 eggs.