Meeting Abstract
Extreme environments are characterized by physiochemical conditions that are stressful for most organisms, often resulting in modifications to organismal biology. Metabolism is critically important for an organism’s ability to respond to environmental stress, as it is directly tied to energy homeostasis. This may be especially important for organisms that inhabit hydrogen sulfide (H2S) environments. H2S directly binds to cytochrome c oxidase, disrupting electron transport and inhibiting aerobic ATP production. Theory suggests that this should result in modifications of metabolic physiology in organisms that persist in these toxic environments, however, few studies have addressed this hypothesis in natural systems. To test whether variation in metabolic physiology exists between sulfidic and non-sulfidic populations, we measured the metabolic rates of two population pairs of Poecilia mexicana. P. mexicana has repeatedly colonized H2S springs in Southern Mexico. These replicated colonization events allow for the comparison of physiological mechanisms used to cope with the extreme conditions imposed in these habitats. We used intermittent-flow respirometry to compare standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) under non-sulfidic conditions and closed-chamber respirometry to measure RMR under both sulfidic and non-sulfidic conditions. We found that SMR was significantly increased in one population of sulfide spring fish, but there were no differences in MMR or AS across all populations measured. Fish from sulfidic populations were able to maintain RMR upon exposure to H2S, while the non-sulfidic populations showed a significant decrease in metabolic rates. This study provides insight into the physiological mechanisms organisms use to maintain energy homeostasis under extreme environmental conditions.
