Source: Wikimedia Commons

Most scientists who work directly with animals have no trouble telling different species of their favorite organisms apart. For example, you’d expect a primatologist to know the difference between a rhesus macaque and a proboscis monkey. In this case, the difference is obvious—even everyday people can pick out a proboscis monkey, with its giant schnozz.

But when it comes to some of the most evasive creatures of the deep—deep-sea octopuses, for instance—the trait differences between species aren’t so easy to pick out.

A new study in Marine Biology decided to tackle this problem by comparing two deep-sea octopus species on a range of physical characteristics. And when we say “deep sea,” we’re talking, like, the bottom of the ocean.

These two species can live as deep as 9,500 feet, or nearly 1.8 miles beneath the surface of the water. Both are actually rather adorable looking, and pink or purple in color—who knew these adorable creatures were lurking so far down? They do share one obvious difference, and that’s where they live. One of them lives in the Atlantic. The other lives in the Pacific. (You’d think the fact that these two oceans are kinda on opposite ends of the planet might help scientists tell them apart?)

Seems like they needed another way. And it just so happens that they found one. Their warts.

Source: Wikimedia Commons

Yep, you read that right. Both species have raised bumps on their heads (scientists call this part of the octopus the “mantle”) and tentacles. But one species—the Pacific deep-sea octopus—is the definite winner in the wart department. They have bumps that go further down their tentacles and mantles.

Just how big is this discovery for those deep into deep-sea research? Huge.

Janet Voight is the Associate Curator of Invertebrates at Chicago’s Field Museum. She claims that differentiating between species is the “basis” for understanding them. “You can really talk about a species if you can’t separate it from others like it,” she explained to Science Daily.

One of the paper’s co-authors, Pennsylvania State University’s Jessica Kurth, explained that this new knowledge that deep-sea octopus species can be differentiated according to their “skin texture”—nice euphemism—will help to advance the study deep-sea creatures.

Though the species already went by different names (Graneledone pacifica and Graneledone verrucosa), this is the first piece of research to actually pit them against each other wart for wart. The authors analyzed a total of 72 octopus specimens, most of which came from Voight’s museum collections. They devised a method to “quantify” the subtle differences in wart location that mark each species.

Source: Wikipedia

Sometimes, scientists use DNA analysis to pick out differences between species. But in this case, it wasn’t possible. The specimens were collected in the 1950s, and as a result their tissue isn’t suitable for DNA work.

Voight points out that we have a lot in common with these complex creatures, even if we’re only distant relatives. And, she adds, “[They’re] some of the smartest animals we know.” She admits it’s not “glamorous” research, but someone had to do it.

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