The octopus already is an oddball of the ocean. Now biologists have rediscovered a species of that eight-arm sea creature that's even stranger.

With their shifting shapes and uncanny intelligence, octopuses "are one of the most mysterious and captivating species," said Rich Ross, a senior biologist at the California Academy of Sciences. "They're aliens alive on our planet and it feels like they have plans."

For Ross and colleagues, it got stranger when they got a batch of octopuses from Central America. The critters just didn't fit the loner denizen-of-the-deep profile that scientists had drawn for the rest of the 300 or so octopus species. Couples of this species can live together to mate for a few days in the same cramped den or shell. While other male octopuses mate from a distance to avoid being cannibalized, these octopuses mate entangled beak-to-beak.

They clean out food waste from their dens. They twirl their arms like an old-timey movie villain with a mustache. And they quickly learn that people mean food: when someone enters the room, they head to the top of the tank. "It's the most amazing octopus that I've ever gotten to work with," Ross said.

Associated Press