A white squid sat on the seabed, gently waving its short, stubby arms and peering beady-eyed into the camera of a deep-diving robot.
That was in 2016, in waters off Hawaii, at a depth of 4,290 meters (2.6 miles). No one had ever seen an octopus like it, and certainly not this deep. Based on its ghostly appearance, it was nicknamed Casper.
Until then, the only octopuses filmed at such depths were Dumbo octopuses, named after another cartoon character, seen swimming around as deep as 6,957 meters, with elegant, ear-like flaps on either side of their heads.
The ocean is one of the world’s last truly wild spaces. It abounds with fascinating species that sometimes seem to border on the absurd, from fish that look up through transparent heads to golden snails with iron armor. We know more about deep space than deep oceans, and science is only beginning to scratch the surface of the rich diversity of life in the deep.
As mining companies push to industrialize the seabed and global leaders continue to wrangle over how to protect the high seas, a new Guardian Seascape series will profile some of the most recently discovered weird, wonderful, majestic, ridiculous, hardcore and sensational creatures. They reveal how much there is still to learn about the least known environment on Earth – and how much there is to protect.
The sight of Casper was a striking moment for Janet Voight, assistant curator of invertebrate zoology at the Field Museum of Natural History in Chicago. “This is completely new and different,” she says, recalling the discovery.
The first glimpse of Casper threw up many intriguing mysteries. Why is it so pale? Most other squids have colorful chromatophores in their skin that change their appearance in an instant and act as camouflage to confuse predators.
Is this a breakthrough in squid evolution?
Janet Voight, octopus expert
Even in the deep sea, squids can be colorful, like the purple, warty one Graneledone. Some use a cloak of dark skin pigments, apparently to hide glowing, luminescent prey they grasp in their arms and thus avoid alerting other predators. Voight guesses that Casper’s paleness may come down to a lack of pigments in his food.
Another puzzle is the short arms, although Casper is not alone in having a limited reach. “The shallower and more tropical you are, the longer and thinner your arms,” says Voight.
This trend towards shorter arms in deep-dwelling cephalopods has no definite explanation. Voight believes that instead of reaching out to grab food, they developed an alternative tactic of twisting their bodies around so that their mouths, on the underside of their bodies, are directly above the food.
Scientists have learned more about Casper by sifting through five years of archived footage collected on deep-sea surveys across the Pacific Ocean. They discovered dozens like Casper sitting on the seabed, from two different species.
“They may be quite common,” says Voight. “It’s just an indicator of how little we know about what’s down there.”
For Voight, especially exciting were the Caspers with their arms wrapped around claws of eggs attached to tall sponges. Previously, she had theorized that bottom-dwelling octopuses need hard rocks to lay their eggs on. Further down, there may be fewer exposed rocks, limiting how deep they can go.
Related: Discovered in the deep: the snail with iron armor
“Casper showed there are ways to avoid that by finding a sponge stalk,” she says. “Is this a breakthrough in squid evolution?”
The sponges themselves are attached to rocky nodules that are scattered over areas of the abyssal plains and take millions of years to form.
If other deep-sea octopi are anything to go by, female Caspers probably spend a long time guarding her eggs. An octopus from another species (Graneledon boreopacifica) was spotted off the coast of California, on a steep slope in the Monterey Canyon, brooding her only clutch in the exact same spot for more than four years.
For now, the pale and mysterious Casper octopuses have yet to be officially named, because all we know about them comes from photos; no one has been able to collect a specimen to study in detail.
“With an octopus, you really need it in your hand,” says Voight.