In the cold, dark waters of the Gulf of California, a strange octopus has been discovered watching over its incubating young.
In the depths, far below the reach of sunlight, the remote-controlled vehicle spotted a type of cephalopod that few, if any, humans would see. She clutched a clutch of eggs tightly in her arms.
That would be unusual enough in itself; few octopuses lay their eggs this way. But these eggs were also unusually huge, twice the size of the eggs of other lecherous squids.
“The deep sea is the largest living space on Earth, and there is still much to discover,” says marine scientist Steven Haddock of the Monterey Bay Aquarium Research Institute (MBARI).
“Our unexpected encounter with giant egg-sucking squid caught the attention of everyone in the ship’s control room. This remarkable sighting underscores the diversity of ways animals adapt to the unique challenges of life in the deep.”
While the reproductive strategies of a number of squid species remain a mystery, those we do usually know something about they take a drop-and-run approach to parenting, where the eggs are left in giant, terrifying, gelatinous balls of slime or deposited directly on the sea floor.
But we know even less about the reproduction of squid in the deeper parts of the ocean, where our survey has barely penetrated.
We are starting to learn more with remote controlled vehicles. Researchers who operate these scientific vessels from a ship on the surface have now seen a line of deep-sea squid carrying hundreds of eggs bound together in a sail that allows the mother to watch over them as the precious young grow and hatch into paralarvae that can swim freely and nurse about yourself.
The recently reported sighting of this particular octopus and her young occurred on an expedition to the Gulf of California in 2015. On one of her dives, an ROV Doctor Ricketts came across the beast hanging out at a depth of 2,566 meters (8,419 ft), right in the middle of the bathypelagic zone.
Although the MBARI ROVs have spotted a total of 17 dying squid so far, most of them have sheets of smaller eggs that carry an estimated 3,000 at a time. This octopus was carrying only a few eggs—perhaps 30 or 40, the researchers estimated. And each egg was large, up to 11.7 millimeters (0.46 in) in diameter.
It probably belongs to the family Gonatidae, or arm octopus. And while she’s the first squid we know of with such large eggs, other squid species that lay large eggs give us an idea of ​​the advantages of bigger versus more numerous.
Of course, having more offspring increases the chance that some will survive to adulthood and produce their own baby squid. However, conditions in the bathypelagic region are more stable and predictable than in waters higher up, where food availability or predators might be more of a problem.
This means that larger eggs that hatch into larger, more robust paralarvae might be a better reproductive strategy. This is what scientists have seen in several other (non-living) deep-sea species.
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And carrying the eggs is probably an excellent strategy to keep them safe while the babies develop. Scientists estimate that embryos take one to four years to fully develop, which is a long time for them to be vulnerable. This newly discovered octopus takes the survival of its offspring seriously—so much so that it sacrifices its own.
“The strain takes a toll on the mother squid. She won’t eat while carrying the eggs and eventually dies after the eggs hatch. But her sacrifice increases the chances that her offspring will survive. It’s just one of many remarkable adaptations that can help cephalopods survive in the deep sea,” he explains marine biologist Henk-Jan Hoving, formerly of MBARI, now at GEOMAR-Helmholtz Center for Ocean Research Kiel, Germany.
“Squids play an important role in the ocean – they are wild predators and a vital food source for many animals, even humans – but we still have a lot to learn about the octopuses that live in the deep sea.”
The discovery was documented in a journal Ecology.