Octopus species broods eggs for over four years

If someone were to create an award for the animal kingdom's mother of the year, a remarkably dedicated eight-limbed mom from the dark and frigid depths of the Pacific Ocean might be a strong contender.

Scientists described how the female of an octopus species that dwells almost a mile below the ocean's surface spends about four-and-a-half years protecting her eggs vigilantly until they hatch, forgoing any food for herself.

It is the longest known egg-brooding period for any animal, they wrote in the scientific journal PLOS ONE that was released on Wednesday.

The scientists used a remote-controlled submarine to monitor the deep-sea species, called Graneledone boreopacifica, off the coast of central California.

They tracked one female, recognizable by its distinctive scars, that clung to a vertical rock face near the floor of a canyon about 1,400 meters under the surface, keeping the roughly 160 translucent eggs free of debris and silt and chasing off predators.

This mother octopus never left the oblong-shaped eggs - which during the brooding period grew from about the size of a blueberry to the size of a grape - and was never seen eating anything. The octopus progressively lost weight and its skin became pale and loose. The researchers monitored the creature during 18 dives over 53 months from May 2007 to September 2011.

Bruce Robison, a deep-sea ecologist at the Monterey Bay Aquarium Research Institute in Moss Landing, California, said the species exhibits an extremely powerful maternal instinct.

"It's extraordinary. It's amazing. We're still astonished ourselves by what we saw," Robison said.

Most octopus females lay a single set of eggs in a lifetime and die shortly after their offspring hatch. The newborn of this species are not helpless babies.

The long brooding period enables the hatchlings to come out of their eggs uniquely capable of survival, emerging as fully developed miniature adults that can capture small prey.

At this tremendous depth, there is no sunlight - the only light comes from bioluminescent sea creatures - and it is very cold: 3 C.

"It may seem nasty to us, but it's home to them," Robison said.

During the brooding period, the mother octopus seemed to focus exclusively on the welfare of the eggs.

"She was protecting her eggs from predators, and they are abundant. There are fish and crabs and all sorts of critters that would love to get in there and eat those eggs. So she was pushing them away when they approached her," Robison said.

"She was also keeping the eggs free from sediment and was ventilating them by pushing water across them for oxygen exchange. She was taking care of them," Robison said.

An adult of this species measures about 40 centimeters in length and is a pale purple color with a mottled skin texture.

It eats crabs, shrimp and snails - "pretty near anything they can catch," Robison said.