A Pacific deep-sea octopus called Graneledone boreopacifica has been found to have an egg-brooding cycle of 53 months — the longest period that any animal is known to protect its eggs.

In April 2007, researchers observed a solitary female Graneledone in the Monterey Canyon, off the central coast of California. When they revisited the site a little more than a month later, they found the octopus guarding a newly formed clutch of eggs.