Octopus who nourished eggs for 4.5 years!

Scientists have discovered a deep-sea octopus that protected and tended her eggs until they hatched 4.5 years later - the longest egg-brooding period ever reported for any animal species.

Using a remotely operated vehicle to monitor the Monterey Submarine Canyon in central California, they discovered a deep-sea octopus in 2007 on the seafloor at around 1,400 metres deep.

When they returned at a later date in 2007, the same octopus was sighted up on the rock and guarding a clutch of attached eggs.

The scientists returned to the site 18 times over 53 months to monitor egg development and measure the length of her brooding period from its inception.

Each time the researchers returned, they found the same octopus clinging to the vertical rock face, arms covering her eggs.

Continuous growth of the eggs led scientists to conclude that it was the same clutch throughout.

About 160 eggs hatched sometime between September and October 2011 - 53 months (almost 4.5 years) after the initial May 2007 sighting.

"These results emphasise the importance of parental care in producing well-developed offspring that can cope with the rigours of the deep-sea habitat," said Bruce Robison from Monterey Bay Aquarium Research Institute in California.

The study appeared in the open-access journal PLOS ONE.