Rare Social Octopuses Break All the (Mating) Rules [Video]
Larger Pacific Striped octopus; image courtesy of Richard Ross
Of the hundreds of known octopus species, most are anti-social, practice safe sex (to avoid getting eaten by a mate) and lay just one clutch of eggs before dying.
The poorly understood larger Pacific striped octopus, however, seems to break from these conventions: They are somewhat social, they mate face-to-face, and the females produce multiple batches of offspring.
The octopus is so rare that science has yet to even give it a formal Latin name. But two California researchers are getting intimately acquainted with this creature; one is even breeding them in a spare bedroom at home, the San Francisco Chronicle recently reported.
Not only are these octopuses unusual in their behavior, but they are also striking in their appearance. “The larger Pacific striped octopus is the most beautiful octopus I have ever seen,” Roy Caldwell, a professor of integrative biology at the University of California, Berkeley, who is studying the octopuses in a lab at the university, said in a prepared statement. These octopuses often show a bold black-and-white pattern—in stripes or spots—but can also put on various other displays, for mating or camouflage, for example.
Larger Pacific striped octopus; image courtesy of Richard Ross
The current moniker for these creatures alludes to the smaller but better-studied lesser Pacific striped octopus (Octopus chierchiae). Like the larger Pacific striped octopuses, which have arms spans of some eight to 10 inches, these pigmy octopuses live in intertidal areas in Nicaragua. The lesser Pacific striped octopus females have also been observed laying more than one small group of eggs in their lifespans, but they are not particularly social.
The larger Pacific striped octopuses seem not only to tolerate each other’s presence but also actually to occasionally seek it out. Richard Ross, a biologist for the California Academy of Sciences’ Steinhart Aquarium, has a 100-gallon tank at home; a male and female are currently cohabitating, and another male and two females are waiting in the wings.
“They can cohabitate in pairs,” Caldwell told the Chronicle. “Groups of them are reported to live in colonies of 40 or more individuals.” And, whereas most female octopuses die within weeks or months of laying eggs, “[these] females can lay clutches of eggs again and again,” Caldwell noted.
The larger Pacific striped octopus also takes a novel approach to sex. Many species mate from afar—to avoid being eaten—with the male reaching his specialized hectocotylus arm into a female’s mantel cavity. Some researchers have observed this move happening even while the two octopuses remained in their separate dens. In other species, a male will sidle up to a female or mount her to insert his arm tip.
Larger Pacific striped octopuses mating beak to beak in captivity; image courtesy of Richard Ross
But the larger Pacific striped octopus mates front-to-front, sucker-to-sucker, beak-to-beak. The male still makes use of his hectocotylus arm, but in this case, he does it from an otherwise risky position right near the female’s mouth. “They seem to be rather pretty sexy,” Caldwell told the Chronicle.
The recent scientific history of the larger Pacific striped octopus began in the 1970s, when Aradio Rodaniche, a biologist from Panama working at a Smithsonian Institute research station, observed these strange octopuses while scuba diving in Nicaragua. Rodaniche eventually wrote up some of his observations in a 1991 abstract for the Bulletin of Marine Science. But, Caldwell noted, what Rodaniche had described seemed so incongruous with other known octopus behaviors that his findings were pooh-poohed by researchers at the time, and the octopus passed, once again, into obscurity. Until last year, when Caldwell and Ross began working with the octopus again. “We are thrilled to confirm many of Rodaniche’s observations,” Ross said in a prepared statement.
The eggs laid in captivity have taken 20 to 50 days to hatch into small baby octopuses. The researchers are still experimenting with different food sources (hatchling octopuses are notoriously picky eaters, usually eschewing frozen foods that their adult parents would have happily devoured). “The really hard part is feeding them,” Ross told the Chronicle. “If we can crack that mystery, it will open up all kinds of doors to raising them.”
Rearing more familiar octopus species, such as the common octopus (Octopus vulgaris) and the giant Pacific octopus (Enteroctopus dolfeini), has also been tricky because they tend to eat one another, meaning if there are 50,000 octopus hatchlings, one would need 50,000 individual tanks to raise each baby octopus—or, say, 10 tanks to try to raise 10 chosen survivors. So, while trying accommodating this space demand and the young’s picky palates, sustainable captive breeding programs have faltered, leaving researchers to rely primarily on wild-caught specimens. But with these seemingly social octopuses, scientists may have hit upon a species that will be more amiable to lab—or at least bedroom—breeding.
Caldwell and Ross are working on a formal species description of this surprising cephalopod. The researchers are also planning an expedition to observe them in their natural habitat in Nicaragua, where the octopuses live in the murky waters near the mouths of rivers.
In the meantime, Ross hopes to contribute some of the progeny from his at-home efforts to the Steinhart Aquarium at the California Academy of Sciences, “so the public can see those rare animals, too,” he said.
About the Author: Katherine Harmon is a freelance writer and contributing editor for Scientific American. Her book Octopus! will be published October 31 from Current/Penguin USA. Follow on Twitter @katherineharmon.