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Extreme pinniped divers are extraordinary models to study adaptations to hypoxia/reoxygenation events derived from extreme fluctuations in oxygen levels during deep diving. We analyzed the evolutionary adaptations of the Weddell seal ( Leptonychotes weddellii) and the Northern and Southern elephant seals ( Mirounga angustirostris and M. leonina), which have exceptional diving abilities, reaching depths of over 1000 meters for extended periods up to 90 minutes. To understand the molecular mechanisms underpinning these remarkable adaptations, we conducted a comprehensive comparative genomic analysis of thirteen pinniped species. Our gene family evolution analyses revealed a significant loss of function in genes involved in the enzymatic degradation of glutathione, an endogenous antioxidant that our functional analysis have previously shown to increase rapidly in response to hypoxia exposure in primary cells derived from extreme divers, likely to protect cells against oxidative damage. We also detected adaptive signatures in pathways involved in the optimization of mitochondrial respiration, energy metabolism, DNA repair and cardiovascular regulation in these extreme divers. Notably the Weddell seal exhibited more genes under positive selection compared to the Elephant seals, possibly reflecting adaptations to extreme environmental pressures. Pathways enriched in Weddell seals include those related to fat metabolism, oxidative damage against hydrogen peroxide and membrane lipid remodeling. Our analysis sheds light on the remarkable genomic adaptations that enable extreme pinniped divers to tolerate oxygen fluctuations associated with deep diving while offering valuable insights into their unique physiological and biochemical strategies for overcoming the challenges posed by hypoxia and reperfusion damage. NSF OPP 2020664. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Santillan et al. (Wed,) studied this question.