Extremely Rare and Weird Blind Fish Found in South China Cave

The extremely rare humpback golden line barbel, found in a south China cave Dante Fenolio/San Antonio Zoo

An international team of scientists has found a fish known to be among the most elusive and strangest in the world. This cave-dwelling creature, which has several oddities, is "the most bizarre freshwater fish, and one of the rarest in the world," said Yahui Zhao, a zoologist with the Chinese Academy of Sciences and member of the search team, in a statement. No ecological data exists and other records also are extremely sparse. Just two of these fish have been preserved in museum collections. Before now, the fish was found in just one cave. Scientists first described the fish in 1988, but it had not been documented since then.

The fish is known as the humpback golden line barbel, or Sinocyclocheilus cyphotergous if you are a scientist. Because it has barely any pigment, its skin is pearly white. Although it has vestigial eyes, the fish is nearly blind. Related to carp, koi and goldfish, this species also has a protrusion on its back that looks like a tiny horn, the function of which is entirely unknown. Scientists call the appearance of this fish "otherworldly."

China has a wealth of hidden cavefish. "There are likely dozens of undescribed species remaining to be discovered below China," Danté Felonio, vice president of conservation and research at the San Antonio Zoo, told Newsweek. Felonio says that The Chinese Cavefish Working Group—the team of scientists that found the fish—discovers new species "on every one of their expeditions." Still, this particular fish had evaded detection for decades. "This species has been something of a white whale," said Andy Gluesenkamp, director of conservation at the San Antonio Zoo, in a statement.

Close-up of this extremely rare blind fish Dante Fenolio/San Antonio Zoo

But numerous factors threaten the cave ecosystem in which the fish were found. Because this landscape is in peril, scientists also have been eager to identify problems, document its biological richness and find ways to conserve the environment.

The Chinese Cavefish Working Group includes conservation biologists and other specialists from the Chinese Academy of Sciences, the San Antonio Zoo, the New Jersey Institute of Technology, the University of Alabama-Huntsville, Universidade Federal de São Carolos and Louisana State University. After finding the fish, they brought a few specimens to their laboratory at the Chinese Academy of Sciences for further study. In particular, the researchers want to understand the horn. "This species has an extremely unusual morphology and is different from any other fish in its genus," says Fenolio.

Scientists do not understand the function of the horn on this strange fish Dante Fenolio/San Antonio Zoo

Finding the humpback golden line barbel was not easy. Relying on tips from local fishermen, the search involved steep descents and treacherous climbs. And the caves where the fish were finally found frequently flood in short bursts.

In addition to studying this fish, the Working Group is continuing its search for other rare species. "China has the greatest diversity of cavefishes on Earth," says Fenolio, "and unfortunately we know very little about them."

The pearlescent skin of the humpback golden line barbel Dante Fenolio/San Antonio Zoo
Dr Fenolio exploring a Chinese cave, image by Andy Gluesenkamp
Zoologist Dante Felonio on the expedition to find the cavefish Dante Fenolio/San Antonio Zoo