The word enigmatic may evoke images of mysterious individuals, things that lurk in the shadows, but not usually salamanders. However, if you ask members in the lab of David Hillis to describe the Eurycea salamanders of Central Texas, enigmatic is certainly appropriate.
These creatures are native to aqueous regions of the Edwards-Trinity aquifer. They live in the cavernous limestone rock inaccessible to human observation, except in caves large and safe enough to allow in researchers. These wet places absent of sunlight are a most suitable place for anything enigmatic!
This reality makes it very hard to do research on these salamanders. However, there is a way to detect them using environmental DNA, or eDNA, and this video below with graduate students Ruben Tovar and Thom Marshall, displays in detail how to do it.
Essentially, whenever these salamanders shed skin or poop, their DNA spreads into the environment. A researcher takes a water sample and there is a chance this DNA is present. Testing water for presences of eDNA allows researchers to track when salamanders are occupying the water source from which they sampled.
Importantly and unlike other amphibians, the Texas Eurycea salamanders spend their entire life in water and rely on the pristine aquifer for survival. If water quality is bad (pollution, drought, etc.) they are often the first to be affected. This is why they have earned the status as an indicator species. An indicator species is an organism whose presence, absence or abundance reflects a specific environmental condition.
Ruben explains: “We suspect salamander presences and absences will strongly correlate with temporal fluctuations in water quality. So we are establishing a long term eDNA sampling effort to better understand these trends.”
In past analysis, both positive and negative eDNA results have occurred at known salamander localities. “This has led biologists to believe water quality plays a significant role as a predictor of salamander eDNA,” Ruben says, “and by extension salamander presence at that locality.”
Since water is so crucial to both the salamanders and how researchers can study them, how do severe weather issues like drought affect things? Ruben answers: “Water levels are a parameter for water quality and they have been steadily decreasing across the salamander range. Tracking these trends requires long-term testing of both eDNA and environmental factors. For example, water level, chemistry, flow. This will help us better understand how Central Texas salamanders are responding over time to environmental disruptions like drought.”
Importantly, each sample acquired represents a time stamp for the environmental conditions, and presence or absence of aquifer organisms just like this enigmatic (and dynamic!) Central Texas salamander.
