MOSS LANDING, Calif. -

A deep-sea octopus brooded its eggs for 4.5 years - longer than any other known animal.

Researchers at the Monterey Bay Aquarium Research Institute observed the female octopus during that time as it kept the eggs clean and guarded them from predators.

Every few months for the last 25 years, a team of MBARI researchers led by Bruce Robison has performed surveys of deep-sea animals at a research site in the depths of Monterey Canyon that they call “Midwater 1.”

In May 2007, during one of these surveys, the researchers discovered a female octopus clinging to a rocky ledge just above the floor of the canyon, about 1,400 meters (4,600 feet) below the ocean surface. The octopus, a species known as Graneledone boreopacifica, had not been in this location during their previous dive at this site in April.

Over the next 4.5 years, the same octopus was at the site each of the 18 times the researchers dove there. They could identify the animal by its distinctive scars.

As the years passed, her translucent eggs grew larger and the researchers could see young octopuses developing inside. Over the same period, the female gradually lost weight and its skin became loose and pale. They never saw the octopus leave its eggs or eat anything - not even showing interest in the small crabs and shrimp that passed by.

The last time the researchers saw the brooding octopus was in September 2011. When they returned one month later, they found that it was gone and "the rock face she had occupied held the tattered remnants of empty egg capsules," researchers wrote in a recent paper in the Public Library of Science.

Most female octopuses lay only one set of eggs and die about the time that their eggs hatch. The eggs of Graneledone boreopacifica are tear-drop-shaped capsules the size of small olives.

After counting the remnants of the egg capsules, the researchers estimated that the female octopus had been brooding about 160 eggs.

Their research suggests that, in addition to setting records for the longest brooding time of any animal, Graneledone boreopacifica may be one of the longest lived cephalopods (a group that includes octopuses, squids, and their relatives.) Most shallow-water octopuses and squids live just a year or two.

More of their research can be read about at MBARI's website.