Meeting Abstract
Extreme environments are characterized by harsh physiochemical stressors that push organisms to their physiological limits. Despite the challenges presented by these habitats, life can be found thriving in nearly every example of extreme environment. The question remains whether or not organisms inhabiting similar extreme conditions evolve in similar ways. To test for these, we investigated the mechanisms that facilitate adaptation to hydrogen-sulfide (H2S), a potent respiratory toxicant that directly interferes with mitochondrial function, in evolutionary independent lineages of poecilids, with special emphasis on populations of Poecilia mexicana. Analysis of gene expression across sulfide-tolerant and -intolerant poecilids shows that H2S tolerance is potentially mediated by convergent modification and expression of genes involved in H2S toxicity and detoxification. The primary pathways associated with H2S tolerance were oxidative phosphorylation (OxPhos) and H2S detoxificatiom initiated by the sulfide:quinone oxidoreductase (SQR) pathway. We assessed function of OxPhos enzymes and SQR in response to H2S in three lineages of P. mexicana and show that sulfide-tolerant populations maintain higher OxPhos activity and have higher SQR activity compared to sulfide-intolerant fish. We also found evidence for increased regulation of internal H2S concentrations in sulfide-tolerant fish. Together, these pathways appear to be responsible for the maintenance of mitochondrial respiration rates in sulfide fish even when H2S is present. Our results indicate that convergent adaptations in mitochondrial processes facilitate the colonization of extreme H2S-rich habitats.
