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Biochemical and molecular traits underlying hypoxia tolerance in sculpins

University of British Columbia

Variation in environmental conditions can sometimes impose severe limitations on organismal survival and reproductive success and organisms that live in variable environments have evolved complex traits to cope with or buffer against the environmental conditions. In my dissertation I examined how adaptive evolution and phenotypic plasticity play a role in the ability of nearshore species of sculpin to tolerate low levels of O₂ or hypoxia. I showed that constitutively expressed biochemical traits in the brain correlated with hypoxia tolerance among the different species independent of phylogenetic relationships, suggesting that these traits may have evolved via natural selection in response to hypoxia. A similar correlation was not seen in either the liver or the white muscle. Next, I showed that transcriptionally mediated phenotypic plasticity is likely associated with the difference in hypoxia tolerance between two species of sculpin. The hypoxia-tolerant tidepool sculpin (Oligocottus maculosus) did not alter gene transcription during the ecologically relevant time-frames of hypoxia exposure (up to 8 hours), in contrast to the hypoxia-intolerant silverspotted sculpin (Blepsias cirrhosus). This suggests that the tolerant species may not rely on phenotypic plasticity during a typical environmental hypoxia exposure and instead may rely on constitutively expressed or fixed traits for survival. Only if hypoxia persists do the hypoxia tolerant tidepool sculpins alter gene transcription, for which a large set of genes showed transcriptional patterns that were divergent to the hypoxia intolerant silverspotted sculpin. Lastly, I examined if similar transcriptional responses occur among three species of sculpin all with the same measured hypoxia tolerance. While a high proportion (65%) of clones showed similar transcription patterns among the species, a majority of genes associated with metabolism and protein production showed differences in both short and long exposures to hypoxia. As metabolism and protein production both play a major role in hypoxic survival, transcriptional differences in genes belonging to these biological processes suggests that the species likely use different mechanism to achieve similar overall hypoxia tolerance phenotype. Combined, this work demonstrates how phenotypic plasticity and adaptive evolution play a role in the variation of hypoxia tolerance among species of sculpin living in the nearshore environment.

Text

2015-04-16

Attribution-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/52879

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nd/2.5/ca/