Maternal deep-sea octopus tends its eggs for over four years

If someone were to create an award for "mother of the year" in the animal kingdom, a remarkably dedicated eight-limbed mum 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 about 1.5km below the sea surface spends about 4½ years brooding her eggs, protecting them vigilantly until they hatch while forgoing any food for herself.

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

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, recognisable by its distinctive scars, that clung to a vertical rock face near the floor of a canyon about 1,400 metres 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 eggs and was never seen eating anything. The octopus progressively lost weight and its skin became pale and loose. The researchers monitored the octopus during 18 dives over 53 months.

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