MOTHER SITS ON CHILDREN FOR OVER 4 YEARS

Says it's for their own protection.

It all started in April 2007 when a remotely operated vehicle descended 1,400 metres (4,600 ft) to a bunch of rocks sticking out of the ocean floor off the coast of California.

Video: MBARI

An octopus called Graneledone boreopacifica was spotted clinging to the rock. This is not at all surprising as it's quite a common species down there. This particular individual was a female brooding about 160 eggs, defending them from predators and ensuring they're kept clean and well-oxygenated. This again is not astonishing as such scenes have been witnessed many times before.

The surprise came months and years later... she was STILL at it!

Image: Robison et al

Octopus up in shallow waters only care for their eggs for a few months, but this deep sea super-parent looked after hers for 53 months, or 4 years 5 months. Not only is this longer than any other octopus, it's longer than any other pregnancy or egg-brooding known, beating the 42 month gestation period of the Frilled Shark and the 20 month brooding period of a certain giant, red shrimp from the deep sea.

Scientists returned to the spot 18 times over the next 4 and a half years, and recognised their subject by a small scar in one of her armpits. They watched as the youngsters developed and their little eyes became visible through the eggs. Conversely, they also watched as their mother wasted away, her eyes clouding over as she became increasingly pale and wrinkled.

Image: Robison et al
Empty eggs

They last saw her in September 2011. When they returned in October she was gone and all the eggs had hatched leaving their remnants attached to the rock. Octopods in shallow waters die shortly after their eggs hatch and it appears the same is true of their deep sea kin.

Egg-brooding is a lot of effort, but it really works. We saw recently that at least two species of deep sea squid also get in on the act and carry their eggs around in their tentacles rather than attach them to a rock and swim away like shallow water squid. A good, long brooding period protects the eggs from harm and allows the youngsters time to develop and emerge with all the strength they need to tackle prey and escape predators at an early age.

With regard to our octopus, two questions arise.

Image: Robison et al

Firstly, did she eat anything? At all?! Other octopods don't eat a thing while they brood their eggs but could she really fast for more than 4 years? The very shrimp and crabs that would usually serve as a meal were seen approaching her eggs, but she simply batted them away and made no effort to eat them. The scientists even offered her food from the robot arm of their vehicle, but she didn't show much interest.

It's possible that she withheld a few eggs within her body so she could reabsorb them for nourishment later. She may also feed on any eggs that become diseased or otherwise won't develop. Or maybe she just starves herself the entire time!

Secondly, there's the question of her lifespan. Most octopods spend an entire quarter of their lives sitting on their eggs and only live for a year or two in total. G. boreopacifica spends more time brooding than shallow-water octopods spend alive! If those 4 years looking after her eggs represent about a quarter of her lifespan, she may be among the most long-lived of any cephalopod!

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Check out the paper by Robison et al. on PLOS one.