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Dryad

Rapid hyperthyroidism-induced adaptation of Salmonid fish in response to environmental pollution

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Jul 17, 2023 version files 7.82 KB

Abstract

The streams draining volcanic landscapes are often characterized by a complex of factors that negatively affect hydrobionts and lead to a decline of their populations. However, in a number of cases, hydrobionts ensure the resilience of populations througth a range of rapid adaptive changes. Here, we present both field and experimental data shedding light on the physiological basis of adaptation in populations of Dolly Varden charr (Salvelinus malma) differing in the duration of isolation in volcanic streams contaminated with heavy metals. The study reveals that isolated populations have a physiological phenotype that distinguishes them from the populations inhabiting clean waters. They are characterized by a hyperthyroid status accompanied by an increased metabolic rate, elevated activity of antioxidant enzymes, decreased ionic conductivity of tissues and reduced stored energetic reserves. The experimental data elucidate that hyperthyroidism is an adaptive characteristic enhancing the resistance to heavy metal contamination and shaping the evolution of these populations. The similarity of physiological, developmental and morphological changes in isolated populations suggests a common source and mechanisms underpinning their “evolutionary rescue”. Thus, populations of S. malma trapped in volcanic streams represent a genuine case of a rapid neuroendocrine-driven adaptation to changing environmental stimuli.