The octopus is one of the coolest animals in the sea. For starters, they are invertebrates. That means they don’t have backbones like humans, lions, turtles, and birds. That may sound unusual, but ...

Brazilian reef octopuses, like other types of cephalopods, defend themselves against predators by inking and extending their mantles. Paul Asman and Jill Lenoble via Flickr under CC BY 2.0 Costello ...

Biologists investigated whether octopuses preferred certain arms over others when hunting, rather than using each arm equally. No matter what type of prey came by, each octopus attacked using the ...