Meeting Abstract
Freshwater springs discharging water riched in toxic hydrogen sulfide (H2S) belong to the most inhospitable aquatic habitats, and few organisms have been able to persist in these extreme environments. Yet, over a dozen lineages of poeciliid fishes have colonized and thrive in sulfide springs, providing an opportunity to study mechanisms of adaptation and the role of convergent evolution in animal diversification. We used comparative transcriptome analyses in three sulfide spring lineages of Poecilia mexicana and matching reference populations from non-sulfidic habitats to test hypotheses about mechanisms mediating tolerance to H2S toxicity. Elevated tolerance to environmental H2S could be driven by three mechanisms: (1) Modification the integumentary system that reduce the flux of environmental H2S into the body. (2) Increased capability to maintain H2S homeostasis despite continuous flux from the environment through increased detoxification or decreased endogenous production. (3) Modification of toxicity targets that make individuals more inert to adverse consequences caused by elevated endogenous concentration. Results indicate that about 150 genes are consistently up- or down-regulated across all three population pairs. Functional annotation of shared differentially expressed genes indicate consistent up-regulation of genes associated with H2S detoxification and sulfur excretion. Consistent with H2S’ role in generating oxidative stress and interfering with mitochondrial function, we also found up-regulation of antioxidant pathways as well as differential expression of genes associated with energy metabolism.
