Evolutionary Hot Tub Provides Clues to Life's Diversity

A special watershed in northeastern Mexico may help explain how organisms adapt and evolve.

To Academy research associate Carol Tang, wading, swimming, and snorkeling in bathwater-warm waters under the hot Mexican sun is part of a good day's fieldwork. As relaxing as it sounds, her study site, a group of thermal springs in Mexico's Chihuahuan Desert, is far from a vacation hotspot. However, to Tang these isolated springs are a scientific hotspot. The water's salinity, pH, and temperature vary greatly over short distances, creating the perfect laboratory to study how animals adapt to extreme environments.

dead snails
Due to the seasonal, ephemeral nature of the shallow ponds, often dead snails can be found along the srtand lines which form when water levels drop. These snails are from the Rio Mesquites system.
Photo: Carol Tang

Tang and Roopnarine's work is part of a larger project with the NASA Astrobiology Institute to study all the organisms in this unique ecosystem, from the algae the snails eat to the fish that eat the snails. Examining extreme habitats such as this may one day explain how life originated and diversified on a young, less hospitable Earth or even what we might expect to find on other planets.

looking for snails
Carol Tang strains the mud from the bottom of Puente Orosco stream looking for live Mexipyrgus snails. Snails can be found within the mud, near gravelly substrates, and associated with the lily pads.
Photo: Evan Carson

Tang and Academy colleague Peter Roopnarine study snails of the genus Mexipyrgus, which are found only in this area and inhabit a gamut of diverse microhabitats. By documenting how the animals' shells vary from one location to another, they hope to see the influence environmental factors have on their development. This information will later be combined with genetic studies to investigate whether these adaptations have led to different snail species.

thermal spring
Thermal spring found near the central part of the Cuatro Cienegas basin surrounded by local mountains. The uplift of the mountians and presence of geothermal springs are related to local plate tectonic activity. Photo: Carol Tang