Meeting Abstract
Extreme environments are characterized by harsh physiochemical conditions, resulting in modifications of various facets organismal function in individuals exposed to them. Metabolic physiology is critically important for an organism’s ability to respond to environmental stress, as it is directly tied to maintenance costs and energy demand. This may be especially important for organisms that inhabit hydrogen sulfide (H2S) rich environments. The molecule’s ability to bind to cytochrome c oxidase (COX) effectively disrupts the electron transport chain and inhibits aerobic ATP production. Theory suggests that this effect should reduce metabolic scope in two potential ways either through direct inhibition of mitochondrial function in presence of H2S, or though adaptive modification of target proteins in the oxidative phosphorylation pathway. We measured the aerobic scope in Poecilia mexicana (Poeciliidae), a fish species that has successfully and repeatedly colonized H2S springs in Mexico. Aerobic scope of sulfidic populations with and without H2S-tolerant COX were compared to reference populations from adjacent nonsulfidic habitats. Using intermittent-flow respirometry and exhaustive chase trials, we compared standard metabolic rate, maximum metabolic rate, and aerobic scope between sulfidic and nonsulfidic populations. This allows the testing of how different physiological mechanisms used to cope with H2S impacts metabolic traits. The results of these experiments provide insight into the role metabolic physiology plays in allowing organisms to inhabit and thrive under extreme environmental conditions.
