In late summer of 2015, biologist Dr. Kirk Zigler was up to his knees in the bone-cold water of a Northwest Georgia cave when he encountered a creature as bizarre as it was completely unexpected.
For months, Dr. Zigler and one of his students at Sewanee: The University of the South had been surveying the species living in the region’s vast network of caves. They were looking for everything from spiders to salamanders to beetles, but the last thing Dr. Zigler expected to see swimming past his boots in Catoosa County’s Crane Cave was a Southern Cavefish (Typhlichthys subterraneus).
Less than three inches long, the Southern Cavefish lacks eyes, and its internal organs and blood vessels peek like crimson ghosts through its milky-white, translucent body. Instead of sight, the Southern Cavefish navigates its environment using fluid-filled pores and canals along its body that react to vibrations in the water.
Scientists have documented Southern Cavefish throughout the Cumberland Plateau and in the Ozarks of Southern Missouri and Northern Arkansas, but they had never been seen in the Valley and Ridge Province, a geologic range stretching from Northwest Georgia, Northeast Alabama and Southeast Tennessee along the Appalachian Mountains to upstate New York.
Seeing one beneath the rolling hills of Catoosa County was the biological equivalent of a UFO sighting.
“We were just completely shocked to find them in that strange place,” Dr. Zigler said.
Dr. Zigler reached out to Dr. Bernie Kuhajda, an aquatic conservation biologist at the Tennessee Aquarium Conservation Institute. Dr. Kuhajda has studied various species of cavefish since the early 1990s. Together, the two planned a return trip to Crane Cave to try and recover the mysterious fish and definitively identify it.
Despite no historical record of Southern Cavefish sightings in the area, Dr. Kuhajda said he was confident of Dr. Zigler’s find.
“I thought he’d probably seen it,” Dr. Kuhajda said. “I knew from working in cave systems that you can’t take anything for granted.”
When they returned in November, Dr. Kuhajda donned a snorkel and wetsuit to brave the 55-degree water of the underground pool, also known as The Found Sea. As he swam, he managed to recover one Southern Cavefish and spot a second individual, which evaded him by swimming beneath a ledge.
Seeing any species of cavefish outside its documented range is exciting, Dr. Kuhajda said. The circumstances that lead to cavefish evolution tend to make it unlikely for them to appear at new, previously surveyed sites or for more than one species to be found in the same location.
“Every now and then, cave systems or aquifers that have been separated, whether due to a flood or more erosion of the limestone, become connected, and you can have transfer of a new fish into a new system,” Dr. Kuhajda said. “That’s what’s so cool about cave biology — you never know when you will find something new.”
After sending off a fin clipping of the recovered fish for a genetics study, Dr. Kuhajda and Dr. Zigler began documenting their discovery in a paper co-written with five other specialists. Their findings appear in the 2016 issue of Subterranean Biology, an annual, peer-reviewed journal published by the International Society of Subterranean Biology.
Based on the discovery in Crane Cave, Dr. Kuhajda said, scientists will need to resurvey caves throughout the Valley and Ridge Province to see if the Southern Cavefish’s range is even more widespread than previously thought.
Anywhere it is found, the Southern Cavefish will be good news, both for scientists and for the 150 million Americans whose principal drinking water comes from ground water sources, according to the National Institutes of Health.
“They are great indicators of water quality in those caves and, eventually, people who rely on well water,” Dr. Kuhajda said. “Finding these fishes here is good news for people as well as for the cavefish.”