Adaptation to hydrogen sulfide: A case study in sulfide spring fishes

Hydrogen sulfide (H2S) is a naturally occurring toxicant in some aquatic habitats. H2S readily invades the cells of animals and inhibits the function of mitochondria, curtailing aerobic ATP production. Livebearing fishes (Poeciliidae) that inhabit freshwater springs rich in H2S have been models to investigate how organisms adapt to such extreme environmental conditions. We summarize recent genomic, transcriptomic, and physiological studies that have documented how modification to the function of mitochondria—both in terms of limiting the toxic effects of H2S and an increased ability for detoxification—contribute to the evolution of H2S tolerance. We also discuss how H2S interacts with other environmental stressors to shape evolution of sulfide spring fishes.