Snakes alive! New Mexico Highlands professors discover new species of anaconda

Feb. 21—Why study anacondas?

For Jesús Rivas, who chairs the biology department at New Mexico Highlands University and has been observing the massive snakes for more than 30 years, the answer to that question is simple: "Why not?"

Since 2007, Rivas and his wife, geneticist and fellow Highlands professor Sarah Corey-Rivas, have been collaborating on a project to better understand the famous and sometimes frightening reptiles, which can grow to be several meters long and more than 1,000 pounds.

Alongside a team of scientists from across South America, Europe and Australia, the duo made a surprising discovery: There are two different species of green anacondas — separated by millions of years of evolutionary distinction — slithering through marshy wetlands in much of South America, though researchers long assumed the snakes were all a single species.

Rivas, Corey-Rivas and their team recognized the northern green anaconda as a separate species that likely inhabits a strip of northern South America from the Ecuadorian Amazon to French Guiana.

The implications of the find are enormous, Rivas said: If researchers can discover a new species of creatures as well-studied as anacondas — a species steadily investigated by Western scientists for nearly 300 years — now, what don't we know about less-examined organisms?

"What does it tell us about the species of crickets and moths and butterflies and spiders and fungi and plants that no one is studying? ... The diversity that we might have boggles the mind," he said.

The discovery issues a "renewed call" for conservation, Rivas and Corey-Rivas agreed, to ensure scientists get the opportunity to study the northern green anaconda as well as the world's still-unidentified creatures.

Though their fieldwork has taken them all over South America, Rivas and Corey-Rivas have lived in Las Vegas, N.M., since 2010, when a job opening at Highlands brought the reptile researchers to New Mexico.

"We love it here," Rivas said.

They're fixtures on campus. Each of the scientists teaches three to four courses in biology and evolution per semester, sharing their knowledge with undergraduate and graduate students.

While balancing their teaching responsibilities, Rivas and Corey-Rivas have been slowly compiling evidence of the need to change the ways anacondas are scientifically classified.

For years, biologists believed there were four species of anacondas: green, yellow, dark spotted and Beni, a snake endemic to the Beni region of Bolivia.

But in reality, it's more complicated than that, Rivas and Corey-Rivas found: What scientists long assumed was a single type of green anaconda is actually two genetically distinct species.

Using samples from all over the world — including museum material and green anaconda scale clippings and blood samples collected in the wild — the researchers isolated the snakes' mitochondrial DNA in their lab at Highlands, Corey-Rivas said.

What they found was a 5.5% difference between three genes in the northern snakes' mitochondrial genome and the same three genes in the southern snakes.

That means the two snakes are "really, really different," Corey-Rivas said, with a variance of DNA between 3% and 5% typically indicating a difference in species. By some measures, the genetic difference between northern and southern green anacondas is wider than the genetic difference between humans and chimpanzees.

Additional analysis determined the two species of green anacondas diverged about 10 million years ago, even though the two species look the same.

"They are morphologically identical. The difference is all in the sequence of those genes," Rivas said.

The scientists named the new species of green anaconda Eunectes akayima, embracing a term roughly translating to "great snake" in the language of the Indigenous Carib people of modern-day Venezuela.

But the researchers didn't just sample and sequence DNA from green anacondas. They took DNA samples from the yellow, dark spotted and Beni anacondas, too.

Despite their external differences, the three seemingly distinct species' DNA was shockingly similar: within 1% of each other, Corey-Rivas said.

That level of genetic similarity seems to indicate all three are, in fact, the same species, Rivas said. The finding generates even more questions about the giant snakes' classification confusion.

Rivas and Corey-Rivas' discovery opens up a new line of inquiry about anacondas.

"There's a lot more to study, a lot more to be learned — because everything that we knew about green anacondas, apparently we only know about one of the green anacondas," Rivas said.

The same might be true for an untold number of creatures incorrectly lumped together as a single species, he added.

The find also makes way for conservation efforts targeted specifically toward the northern green anaconda, Corey-Rivas said. Now that scientists know there's a different species of anaconda restricted to northern South America, they can double-down on stewardship efforts in the region to safeguard the future of E. akayima.

Corey-Rivas said she hopes the project — which includes authors from across eight countries and consultation with the Indigenous Baihuaeri Waorani people of the Ecuadorian Amazon — will exemplify the spirit of scientific collaboration for her students, too.

"We're teachers," she said. "We're trying to behave the way we teach students they should be doing science, and I think the paper is a good example of that in giving credit to all of the knowledge that all the collaborators brought."