The cave episode of the documentary "Life in Hell" can now be seen online. Among other caves, the documentary features the Cueva del Azufre system and some of our work.

Our lab has been awarded a grant from the National Science Foundation to study the evolution of fishes in extreme environments. Hydrogen sulfide is a highly toxic gas that is lethal for most animals, even at low concentrations. In southern Mexico, small livebearing fish have independently colonized multiple sulfidic springs, where hydrogen sulfide naturally occurs in high concentrations. These fish provide an opportunity to study how vertebrates have managed to survive in conditions that are lethal for most other organisms. Adaptation in sulfide springs also leads to reproductive isolation between sulfidic and non-sulfidic ecotypes, providing insights about how new species evolve. Understanding organisms’ responses to naturally occurring stressful environments can ultimately be used to better understand causes and consequences of organismal responses to human altered environments. The project fosters collaboration in research and education between scientists and students from the United States and Mexico. The project also establishes a public outreach platform for fish biologists to interact with fish hobbyist organizations as a means to disseminate research findings to the lay public.

Also see the coverage by the Stillwater News Press.

In 2010, we were fortunate to accompany a movie team from Mona Lisa Productions to shoot in the Cueva del Azufre system. That footage can soon be seen on TV in the episode "Creatures of the dark". The "Life in Hell" series will be presented at the International Science Film Festival in Paris in October 2011. The episodes will then air on French and German TV in November (dates for the US are not set yet). Until then, you can get a glimpse at the series through the trailer embbeded below.

Plants and other photoautotrophs are generally considered to be the base of food webs. Organisms in habitats that lack light, such as caves, usually rely nutrients washed in form surface ecosystems for survival. In a sulfur cave in southern Mexico (Cueva del Azufre), however, chemolithotrophic bacteria are using hydrogen sulfide and other sulfur species, instead of sunlight, to produce energy. A recent study published online first in Ecology now showed that these bacteria form the base of the food web, just as plant do in surface environments. Analysis of gut contents and stable isotope ratios of tissues indicated that sulfur-oxidizing bacteria are the predominant source of energy supporting the cavefish Poecilia mexicana. The results provide evidence of a vertebrate deriving its organic carbon and nitrogen from in situ chemoautotrophic production and highlight the importance of alternative energy production sources supporting animals in extreme environments.

Figure 1. A. Map of the study site near the village of Tapijualapa in southern Tabasco state, Mexico. Non-sulfidic surface habitats (AT: Arroyo Tacubaya; RO: Rio Oxolotan) are indicated in blue, sulfidic surface stream (EAI: El Azufre, cave resurgence; EAII: El Azufre, big spring) in yellow, the entrance to the sulfidic cave stream (CA: Cueva del Azufre) in red, and the entrance to the non-sulfidic cave stream (LA: Cueva Luna Azufre) in orange. B. View into the Cueva del Azufre. C. View of the sulfidic surface stream. D. Female cavefish from the Cueva del Azufre with reduced eye size and pigmentation. E. Male fish from the sulfidic surface stream. F. Colonies of purple and G. white sulfide bacteria growing in the sulfidic surface stream.