Scientists Tell Octopus Species Apart by Counting Their Warts

As kids, we were taught that it’s impolite to stare. It’s a good thing not everybody listened. Researchers peering at adorable, pudgy deep-sea octopuses say the placement and number of their warts could be a way of differentiating two very similar-looking species. They published their findings in the journal Marine Biology Research.

Graneledone verrucosa, pictured above, and Graneledone pacifica, pictured below, have an awful lot in common.

They live deep in the sea, sometimes chilling as far down as 9500 feet into the blackness. They’re My Little Pony–colored, big-eyed, and cute as dumplings. And they’re warty as heck.

Previous studies have suggested that these lumps could help distinguish one Graneledone species from another, but deep-sea critters are tricky and expensive to find and collect. The scarcity of specimens has made the wart hypothesis difficult to confirm.

And that’s where museum collections come in. Lead author Janet Voight is associate curator of invertebrates at The Field Museum in Chicago. She and her co-author, Jessica Kurth of Pennsylvania State University, examined 72 different squishy specimens, carefully noting the placement, size, and quantity of each animal’s warts.

“Nobody has sat down with dozens of these octopuses and compared them,” Voight said in a statement. “There are so many things like that in museum collections, just waiting for the right scientist to come along and use the information they offer."

The researchers’ octopus ogling paid off: They found clear, if subtle, differences in the two species’ lump-scapes. G. pacifica was wartier, with more bumps running down its arms and mantle than its cousin has.

The study shows the importance of having multiple specimens to compare, Voight says. "If you only have two individuals, you don't know what's important and what's not—it'd be like meeting a person with blonde hair and a person with brown hair and concluding that they must be different species."

It also illustrates how little we know about animals in the deep sea. "This study should make future octopus analysis easier and more rigorous," Voight says. "I’d be happy if that happened.”