If recent octopus discoveries have taught us anything, it's that these eight-armed ocean dwellers are smart. They can use tools, change color in an instant, and commission their arms to solve problems. But they generally do all this as loners.
Now, new research into a surprisingly social octopus is shattering even the most expansive ideas of known octopus behavior. (Related: "Journey of Octopus Discovery Reveals Them to Be Playful, Curious, Smart.")
Panamanian biologist Aradio Rodaniche first reported the Pacific striped octopus in 1991 off the coast of Nicaragua, noting its strange behavior—living in groups of possibly up to 40, laying multiple egg clutches, and mating face-to-face and sucker-to-sucker. Most other octopus species, for instance, come together only to mate.
But scientists didn't see another one of these curious octopuses for another 20 years, when Richard Ross, a biologist at the California Academy of Sciences, came across one in 2012. Through a commercial collector, he acquired several wild specimens to study in the lab.
Ross is one of the few scientists who are studying and observing some of this octopus's truly bizarre—and sometimes anxiety-provoking—behavior, which he and his team will describe in an upcoming publication.
"Regular octopus mating, where the male is behind and on top of the [female]—or far away—that's scary enough to watch," said Ross. Females of many species, for instance, will sometimes kill and eat their mate, even if they are mating from a distance.
But "watching these guys come and interact with their beaks—wrapped up in a ball of limbs—are they fighting or mating?" he recalled wondering.
The larger Pacific striped octopus has a lot to teach scientists, but raising these invertebrates in captivity is a notoriously difficult endeavor. Aside from usually having to keep them in individual enclosures to prevent cannibalism, researchers have a real problem getting young octopus hatchlings to eat, often losing whole broods in a matter of days.
And what's most troubling for Ross is that he has not yet successfully raised hatchlings into adults—and his captive octopus population is dwindling, with his usual commercial collector unable to ship him any new adults, for unknown reasons.
For octopus researchers, "there seems to be an eternal quest for 'the social octopus,' " said Jennifer Mather, a biologist and octopus expert at the University of Lethbridge in Alberta, Canada.
Other scientists have pointed out that another type of octopus, Abdopus, lives in fairly close proximity. And decades ago Mather herself published work about Eledone, a group of octopuses "who hang around together," she said.
All these hints at social tolerance "suggest a good deal of diversity and plasticity" beyond what we thought we knew about octopuses, saidFrank Grasso, a biologist at Brooklyn College in New York. (Watch a video of an octopus hunting.)
In addition to this gregarious behavior, the larger Pacific striped octopus has challenged our views on octopus reproduction—beyond its lusty mating display.
Instead of laying all their eggs in one basket, so to speak, the females continuously lay broods of eggs, said biologist and octopus expert James Wood. The only other octopus known to reliably hatch more than one batch is the lesser Pacific striped octopus (Octopus chierchiae), a close relative.
This approach has advantages over one-time egg laying, noted Wood: "Why not live to fight another day and reproduce again?" But as a whole, it could also leave the species less able to adapt to changing environmental conditions.
There are hints that other species might be able to reproduce more than once. But the fact that we have few other examples of this reflects the overall lack of knowledge about these animals.
"There are a lot of unknown octopus species in the world," Grasso said. "That may be more common" than we think, he said.
What's more, for most octopuses, breeding seems to kick off what is known as senescence—a rapid wasting that leads to death.
Scientists have assumed that reproduction is tied to this change. But the larger Pacific striped octopus opens up the possibility that "the timing of reproduction is something that is just crammed in before senescence—and may just be coincidental," Grasso said.
Cradle to Grave
That's why the new Pacific species could be a window into this—and other—perplexing aspects of octopus biology.
"These octopuses do so many weird things that being able to study them over generations would be extremely interesting," Ross said. (Watch: "Sneaky Octopus Dismantles Camera.")
But first scientists need to study the animals throughout a single life cycle, from cradle to grave: As Mather points out, "We won't understand animals if we just know what they do as adults."
To that end, earlier this month, Ross and his colleague Roy Caldwell, a biologist at UC-Berkeley, found a food that baby larger Pacific striped octopuses seem to like: the tiny larvae of cleaner shrimps.
"We've suspected that some kind of crustacean larvae would be the way to go," Ross said. And after trying enough kinds, they have finally hit on one that shows promise.
Despite this initial success, Ross has still managed to keep the babies alive for only about 15 days. "It's a race against time now," he said.
"Expecting the Unexpected"
Grasso, of Brooklyn College, said, "If they succeed in doing this, it will be a great accomplishment."
Not only would figuring out how to raise octopuses in captivity help to decipher this new species, but it could also launch the species as a new laboratory model.
In many labs, cuttlefish have taken the place of octopuses because cuttlefish can live harmoniously together. This octopus's ability to share space with others is "a big plus" for research potential, Grasso said.
Overall, one thing that's certain about the larger Pacific striped octopus is that it has reminded us that with octopus behavior, "there may be no outer limits," Ross said.
"We should always be expecting the unexpected."
Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Read more about octopuses in her book Octopus! The Most Mysterious Creature in the Sea and on her blog Octopus Chronicles.