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Biodiversity Blog


Creatures of Halloween: Widemouth Blindcat (Satan eurystomus)

By Dean Hendrickson (Curator, Ichthyology Collection) and Nicole Elmer

 Satan eurystomus (Photo: Garold Sneegas)

In our last Halloween posting, the scorpionfly donned orange, black, and yellow. The species in this blog’s focus is pale and pink. This is Satan eurystomus, also known as the Widemouth Blindcat, a cave catfish, known only from deep below the city of San Antonio, Texas. As is the critter itself, the thought that it might be extinct, is equally scary, given Satan’s dependence on the same vital liquid that sustains all of us humans. 

Like any good scary tale, the star of this story is wrapped in mystery. The specimens that we do have in the Ichthyology Collection are rare, and the fish itself is near impossible to study. What is known about them is they have transparent skin, no eyes, and live in total darkness in the Edwards Aquifer below San Antonio. The transparent skin allows their blood to show through, giving them their pink appearance. What we also know is they are almost certainly like most deep-sea fishes, “vulnerable to disturbance because of late maturation, extreme longevity, low fecundity and slow growth." Aquifer mining and other forms of human intervention have almost surely impacted their habitat - the City of San Antonio for many years was the world’s largest city, wholly (and now still mostly) dependent on subterranean water - including that of Satan’s home, more than 1,000 feet below the city.

The only way to obtain specimens of this species is by netting them from the water wells which are almost all now pumped to supply water to San Antonio, and although there are thousands of wells in the Edwards Aquifer, this species is known only from a small number of those, all near, or a short distance south of, downtown. Most of the wells from which specimens were obtained are now plumbed directly into the city’s treatment plants and water distribution system, eliminating ways to sample, and water supply managers are rightfully protective of the integrity of that infrastructure that supplies water to their more than 1.8 million customers. Any proposals to divert water to nets or insert sampling devices into their plumbing would be very carefully assessed. Frankly, they also worry about allowing sampling for a species that might likely be determined to be endangered, with consequential impacts of that on their operations. Drilling of new wells more than 1,000 feet deep and large enough to allow passage of remotely operated submersible exploration equipment, such as that used in deep-sea science, would obviously be extremely costly, not to mention, unlikely to be permitted. 

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As Texas’ aquifer systems decline, the habitat of this and other cave fishes diminishes or changes. But, researching Satan, and other aquifer organisms can help us better understand and manage the invaluable underground water that supports both humans and amazingly diverse subterranean aquatic ecosystems. (See "Creatures of the Deep Karst" in American Scientist https://doi.org/10.1511/2019.107.5.260, and "Biology and ecology of the Edwards Aquifer" https://doi.org/10.1130/2019.1215(13)). Though the last collection of a specimen of Satan was 35 years ago, we remain hopeful that the species is still alive and thriving deep under San Antonio. However, the outlook is not good - biological monitoring efforts from 2008 through 2014 in and near wells that historically produced specimens, failed to yield even a single individual, whereas comparable surveys in the 1970s produced many.

Read more here about the amazing Edwards Aquifer blindcats (yes, Satan’s not alone down there). Texas also has the Mexican blindcat over by Del Rio. (https://sites.cns.utexas.edu/hendricksonlab/mexican-blindcat)

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