An eyeless catfish with translucent skin, never before seen in the U.S., was identified in Texas this May.

The finding of the endangered fish, which was previously only seen in Mexico, supports the theory that water-filled tunnels and pores connect Mexico and Texas portions of the Edwards-Trinity Aquifer.

Dean Hendrickson, curator of ichthyology at The University of Texas at Austin, said the tunnel system within the aquifers allowed the fish to travel from Mexico to the U.S. underground. 

“As a result of the connection, it is the first time that a foreign endangered species has turned up naturally occurring in the U.S., then immediately had legal endangered species protection under the U.S. government,” said Hendrickson. 

Hendrickson identified the fish as the Mexican blindcat (Prietella phreatophila). The fish was discovered in the deep waters of a limestone cave at Amistad National Recreation Area near Del Rio, Texas. Previously, the blindcat has only been spotted in caves and springs in the northern Mexican state of Coahuila. 

To locate a living blindcat in Texas, Hendrickson worked with the National Park Service and Zara Environmental, an environmental consulting company. The blindcat was captured after five separate expeditions involving hiking through the desert, rappelling down narrow caves and free diving underground water holes. 

Sporting a pale pinkish color due to the visibility of blood through its translucent skin, the Mexican blindcat grows no more than four inches in length. It is now one of three blind catfish species found within the United States.  

“The blindcat has the peculiar quality of floating like a dead fish near the surface in order to conserve energy,” Hendrickson said. “They are fascinating creatures that point clues to evolutionary pressures of underwater cavernous systems.” 

Jean Krejca, owner of Zara Environmental, helped oversee the expeditions to find the catfish. 

“The blindcat is difficult to detect because it’s only by chance that it may swim into a cave accessible to humans,” Krejca said. “Ninety-five percent of its habitat is in tiny holes of rock formations deep within the earth.” 

Although Krejca was part of the team leading the expeditions, it was Peter Sprouse, vice president of Zara Environmental, and Jack Johnson, the National Park Service resource manager at Amistad, who captured the fish. Johnson first spotted the fish during a routine cave inventory in spring 2015, and he proceeded to work with Hendrickson and Zara Environmental to officially document the catfish. 

“Any conservation efforts for cave dwelling species is in our self interest because their livelihood is a good indicator of water quality in various areas,” Sprouse said.  “The important steps are now to determine where the species thrive.” 

Hendrickson hopes to develop a program for extensive water sampling using a DNA technique called eDNA to detect the extent of Mexican blindcat populations. eDNA is a newly developed procedure that identifies DNA of target species using water, dirt or feces samples. 

“Finding DNA fragments from the blind catfish in caves where we cannot physically see them will confirm their presence and identify their locational reach,”
Hendrickson said.

The specimens collected in May have been relocated to a facility in the San Antonio Zoo’s Department of Conservation and Research designed to care for cave-dwelling
aquifer organisms. 

“Steps moving forward include gene seqmuencing to verify their scientific name,” said Krejca. “I was stoked when we found it, but research and conservation efforts are now key objectives ahead that may provide more surprises.”