The toothless blindcat is a troglobitic catfish of the family Ictaluridae. It was named Trogloglanis pattersoni by Eigenmann in 1919. It is considered to be the most highly specialized member of the family. It is unique in having no eyes, no pigment, no air bladder, and a sucker-type mouth. It is found only in southern Bexar County at depths of 1,350 to 2,000 feet below the surface, in the water-filled caverns of the Balcones Fault Zone Edwards Aquifer. It was discovered originally by George W. Brackenridge in one of his wells. Later a Belgian farmer, Josef Boecke, noticed the fish in the discharge from his artesian irrigation well near the site of the present Joe Freeman Coliseum in San Antonio. In 1977–78 a study of the Bexar County groundwater fauna was conducted by Glenn Longley and Henry Karnei. They collected twenty-six specimens of this species and gained much information regarding its ecosystem. The toothless blindcat apparently feeds on organic materials in the water-filled caverns of the aquifer. It is possibly dependent on having the anaerobic "bad water" nearby. It is suggested that the species is dependent on the sulfur bacteria-based food chain that develops in the saline, sulfurous zone found adjacent to the good-quality Edwards Aquifer. It is unable to withstand the absence of dissolved oxygen but may make short excursions into that area to feed. It is likely that there is a sharp division (halocline) between the good water and "bad water" of the aquifer in this area. Overpumping of the aquifer presents a threat to the species. In the 1990s the world's largest water well was drilled close to the known habitat of the fish. Drawing down the aquifer poses a threat to the toothless blindcat by possibly allowing the poor-quality "bad water" to replace good-quality water where the fish now resides.