The larger Pacific striped octopus hunts shrimp using a strategy worthy of a schoolyard prank. And that’s not the only oddity about the species. It’s only the second octopus known with females that prolong motherhood, instead of dying after weeks of all-out coddling a single brood.
But what everyone wants to talk about, researchers who study the species have found, is beak-to-beak mating.
Before writhing, wrestling videos of the larger Pacific striped octopus (nicknamed LPSO), biologists knew of two forms of eight-armed sex. Some species mate at a distance, says Roy Caldwell of the University of California, Berkeley. The male extends one arm, always the same one, toward the female and up under her mantle. A travel-ready package of sperm emerges onto his skin and settles into a specialized groove on his mating arm. Waves of arm flexing resembling mammal intestinal motions nudge the packet toward one of two openings to her reproductive tracts.
Distance mating has other challenges. In an Indonesian octopus species, Caldwell’s former student Christine Huffard of the Monterey Bay Aquarium Research Institute discovered males hunkered in their dens sending an arm across the seafloor into the den of the female next door. On occasion, such females leave their dens on some octopus errand, dragging the male along by his mating arm.
In some small species, such as blue-ringed octopuses, a male positions himself against a female’s mantle while reaching around and underneath with the mating arm. But Caldwell, Huffard and colleagues report August 12 in PLOS ONE that LPSOs in the lab routinely coupled with arms spread back, mouth to mouth.
“They actually line up their arms,” Caldwell says. He’s seen LPSO pairs matched eight to eight. And it looks chancy. There’s grappling, and sometimes a female engulfs the male with her arms and web — both moves that octopuses make when they fight. Afterward, males show marks left by female suckers.
LPSOs have subtler moves when offered a shrimp. Unlike other octopuses, the LPSO doesn’t just pounce. It eases out one arm slowly, slowly, and then just taps the shrimp on the shoulder. The shrimp startles into flight — often directly into the octopus’s arms.
BEAK-TO-BEAK Watch two larger Pacific striped octopuses mate in their trademark style.
Credit: Caldwell et al. (video); Bensound (music).