In the cold, dark waters of the Gulf of California, a strange squid was discovered watching over its nesting young.
At depths far below the reach of sunlight, a remotely piloted vehicle spotted a species of cephalopod that few humans – if any at all – would have seen. Clutched tightly in her arms was a clutch of eggs.
This in itself would be unusual enough; Very few squid hatch their eggs this way. But these eggs were also unusually huge, twice the size of the eggs of other breeding squids.
“The deep sea is the largest living space on Earth and there is still much to discover,” said marine scientist Steven Haddock of the Monterey Bay Aquarium Research Institute (MBARI).
“Our unexpected encounter with a squid hatching giant eggs captured the attention of everyone in the ship’s control room. This remarkable observation highlights the diversity of ways animals adapt to the unique challenges of life in the deep.”
Although the reproductive strategies of some squid species remain a mystery, we generally know something about the species have a drop-and-run approach to parenting, where eggs are left in giant, creepy, gelatinous slime balls, or deposited directly on the seabed.
But we know even less about squid reproduction in the deeper parts of the ocean, where our explorations have barely penetrated.
With remotely operated vehicles we are starting to learn more. Researchers who operate these scientific vessels from a ship on the surface have now spotted a number of deep-sea squid carrying hundreds of eggs, tied together in a sheet allowing the mother to watch over them while the precious babies grow and hatch into paralarvae that swim freely and for take care of themselves.
The recently announced sighting of this particular squid and its babies occurred during an expedition to the Gulf of California in 2015. During one of its dives, ROV Doctor Ricketts encountered the beast loitering at a depth of 2,566 meters (8,419 feet), right in the middle of the bathypelagic zone.
Although MBARI ROVs have seen a total of seventeen breeding squid so far, most of them have skins containing smaller eggs, which are estimated to carry as many as 3,000 at a time. This mama squid was carrying just a few eggs — perhaps 30 or 40, the researchers estimated. And each egg was large, up to 11.7 millimeters (0.46 inches) in diameter.
She probably belongs to the family Gonatidae, or arm hook squids. And although she is the first breeding squid we know of with such large eggs, other species of squid that lay large eggs give us an idea of the advantages of larger versus more numerous.
A greater number of offspring naturally increases the chance that some will survive into adulthood and create their own baby squid. But conditions in the bathypelagic region are more stable and predictable than the waters above, where food availability or predators could be a greater concern.
This means that larger eggs that hatch larger, more robust paralarvae could be a better reproductive strategy. This is what scientists have seen in a few other (non-breeding) deep-sea species.
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And carrying the eggs around is likely an excellent strategy for keeping them safe while the babies develop. The researchers estimate that it takes one to four years for the embryos to fully develop, which is a long time to be vulnerable. This newly discovered squid takes the survival of her offspring so seriously that she sacrifices her own life for it.
“Breeding takes a lot out of a mother squid. She doesn’t eat while she’s carrying her eggs and eventually dies after her eggs hatch. But her sacrifice increases the chances that her offspring will survive. It’s just one of many remarkable adaptations that may be possible. are.” help cephalopods survive in the deep sea,” explains marine biologist Henk-Jan Hoving, formerly of MBARI, now at the GEOMAR-Helmholtz Center for Ocean Research Kiel in Germany.
“Squids play an important role in the ocean – they are fierce predators and an essential food source for many animals, even humans – but we still have a lot to learn about the squids that live in the deep sea.”
The discovery is documented in the journal Ecology.