‘Large’-eyed river creature baffled experts — until now. See the new species (2025)

In a small river of central Africa, a “large”-eyed creature swam through the fast-flowing water — or tried to, at least, as something caught it and pulled it toward the surface.

Scientists looked at their catch. They didn’t know it at the time, but they were looking at a new species.

Biologists Tobit Liyandja and Melanie Stiassny set out to study a group of African fish known as Labeo, a type of carp, with a history of underestimated diversity and confusing classifications, they wrote in a study published April 20 in the peer-reviewed Journal of Fish Biology.

As part of the project, researchers encountered a “particularly problematic” group of fish from the Niari River in the Republic of the Congo, the study said. Scientists had known about these fish for years but had trouble identifying them.

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Liyandja and Stiassny took a closer look at a few of these Niari River fish, caught between 2010 and 2013. They did CT scans of the fish, tested their DNA and scrutinized their physical features. A pattern began to emerge: the Niari River fish were subtly but consistently different from other known species.

Researchers realized they’d discovered a new species — Labeo niariensis, or the Niari carp — and resolved a “longstanding case of repeated misidentification.”

Niari carp are considered “small-sized,” reaching just over 5 inches in length, the study said. They have “relatively large” heads with “large” eyes, moderately sized mouths and “prominent” snouts.

Photos show several Niari carp after being caught and preserved. Overall, their bodies are dull brown.

Niari carp were found in rivers “with a strong current” and are likely bottom-dwellers but much about their lifestyle remains unknown, the study said.

Researchers said they named the new species after the Niari Department where it was first discovered and, so far, the only place where it has been found. The department, which includes a river system with the same name, is in the southern Republic of the Congo and borders Angola, the Democratic Republic of the Congo and Gabon.

A 2020 YouTube video shared by Christian Mpea shows a river in the Niari Department.

The new species was identified by its DNA, skeleton, fin shape and other subtle physical features, the study said.