Scientists discover an eyeless cavefish in Alabama and name it after ‘Stranger Things’ monster

Bobcat Cave near Huntsville is home to the endangered Alabama cave shrimp, two species of cave crayfish and the southern cavefish. Those were all Dr. Matthew Niemiller expected to find when he set out to survey the cave system last year.

Instead, he discovered a bizarre-looking fish, previously unknown to science. Niemiller said he believes this fish may be among the rarest in the world.

The newfound species is eyeless and features a hunchback, spiny rays and a snout shape unlike that of other cavefish species. What's more, the fish completely lacks pigment; beneath its translucent skin, you can see its brain.

This transparency isn't that uncommon, said Dr. Jonathan Armbruster, curator of fishes at the Auburn University Museum of Natural History in Auburn, Alabama, and a coauthor of a recent study on the discovery.

"You usually see it in the smaller fishes, things that live in open water," Armbruster said. "They'll often have a clear body so that they can be cryptic in the clear waters."

The creature resembles the stuff of sci-fi dramas — and, fittingly, it has been dubbed Demogorgonichthys arcanus, or demon cavefish, a name derived from the monster Demogorgon in the Netflix TV series "Stranger Things."

Initially, Niemiller, the new study's lead author, was uncertain whether the fish belonged to a previously discovered species: the southern cavefish.

"Over the years, I've seen how variable cavefish can be, and I've been fooled before by animals that looked different but were genetically very similar," said Niemiller, an associate professor of biological sciences at the University of Alabama in Huntsville. "But this one was different in ways that kept holding up."

Niemiller shared photos of the fish with Armbruster and Dr. Pamela Hart, an assistant professor of biology at the University of Alabama who is also a coauthor of the study.

Upon comparing the specimens with the southern cavefish, Armbruster said he started noticing the differences. The team performed CT scans, genetic tests and other analysis on the fish and discovered that these bizarre-looking creatures were skeletally different from other already identified animals in the cave.

Based on these results, the researchers described the fish as a newly identified genus and species.

It's unclear how many demon cavefish exist, but they may be among the rarest fish in the world, Niemiller said. "The species is known from a single site based on our best knowledge with presumably a very small population size," Niemiller wrote in a text message.

The team's findings were published July 6 in the journal Scientific Reports.

A name fit for a sci-fi creature

In the series "Stranger Things," a monster named Demogorgon stalks the fictional town of Hawkins, Indiana. The origins of the word Demogorgon are unclear; while scholars theorize that it has Greek roots, creators of the role-playing game Dungeons & Dragons, which debuted in the 1970s, adopted the name for a villain. Decades later, Netflix used it for the "Stranger Things" monster.

When the demon cavefish was discovered, "Stranger Things" was close to releasing another season. Armbruster, a longtime fan of the series, suggested naming the fish after the Demogorgon.

"What do you call a plain white, eyeless, rather nondescript thing? I mean, it's hard to come up with descriptive names for something like that, and so what you'll see is a lot of cave organisms have some kind of tie-in with underground creatures of some sort," Armbruster said.

Little is known about this cavefish. Researchers aren't able to tell male and female fish apart, and they have "zero clue" about its reproduction, Armbruster said.

As for what it feeds on, the demon cavefish likely eats whatever can fit in its mouth, Armbruster said.

A sign of more unidentified species

The discovery of the demon cavefish also suggests there could be other unidentified species, even in intensively studied areas, according to the study. These species may take refuge in access-restricted lands, such as military installations, the study said. Bobcat Cave, the site of the demon cavefish's discovery, is beneath the US Army's Redstone Arsenal.

Dr. Suzanne McGaugh, a professor at the University of Minnesota who studies the evolution of cavefish, described discoveries of new North American vertebrate species such as the demon cavefish as "exceedingly rare."

It's amazing that two cavefish species live in the same cave despite evolving through separate journeys from different ancestors, McGaugh said, referring to the demon cavefish and southern cavefish.

The last time he was in Bobcat Cave, Niemiller said he saw 27 demon cavefish, but this number likely isn't indicative of the entire population. Still, the recharge basin, which influences the amount and quality of groundwater entering the system, is "very small," Armbruster said, indicating the demon cavefish is likely critically endangered.

Because water quality protections are already in place near the cave, Armbruster said it's "pretty unlikely" the fish will go extinct.

Cave organisms can be like "canaries in a coal mine," Armbruster said. If populations fall, it is possible that the groundwater is contaminated.

Through identifying the demon cavefish, scientists are a step closer to solving the planet's biodiversity crisis, he added. "We need to understand what our planet is like in order to make sure that we survive into the future," Armbruster said. "It's great we can keep cave fish alive, but ultimately, it's about our own survival as well."

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