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

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 r..., Immediately after sampling, blood was sampled from the caudal vessel of fish using vacutainers with K2EDTA (Galen). Then, the blood was centrifuged for 3 min under 1900 g (velocity-6µ, Dynamica), and a supernatant (plasma) was collected and frozen for further hormonal (cortisol and total T3) content analysis. The left lateral body muscle, peeled from skin and blood, and a caudal fragment of the liver (both 0.10 ± 0.01 g) were sampled for the analysis of stored energetic resource by assessing of the triglycerides and glycogen concentrations, respectively (Schlenk et al., 2008). The remaining part of the body was gutted (removal of coelomic organs) and frozen at -50⁰C for further analysis of the activity of antioxidant enzymes and ATP-ase ion pumps.
The set of biochemical parameters was measured spectrophotometrically using the photometer StatFax 303 Plus (Awareness Technology). The fish tissues were homogenized using TissueLyser (Qiagen), centrifuged for 5 min at 1900 g (velocity-6µ, Dyn..., Kingsoft Spreadsheets, OpenOffice Calc, Google spreadsheets