Abstract
Thermoregulation in ectothermic animals is influenced by the ability to effectively respond to thermal variations. While it is known that ectotherms are affected by thermal changes, it remains unknown whether physiological and/or metabolic traits are impacted by modifications to the thermal environment. Our research provides key evidence that fish ectotherms are highly influenced by thermal variability during development, which leads to important modifications at several metabolic levels (e.g., growth trajectories, microstructural alterations, muscle injuries, and molecular mechanisms). In Atlantic salmon (Salmo salar), a wide thermal range (ΔT 6.4°C) during development (posthatch larvae to juveniles) was associated with increases in key thermal performance measures for survival and growth trajectory. Other metabolic traits were also significantly influenced, such as size, muscle cellularity, and molecular growth regulators possibly affected by adaptive processes. In contrast, a restricted thermal range (ΔT 1.4°C) was detrimental to growth, survival, and cellular microstructure as muscle growth could not keep pace with increased metabolic demands. These findings provide a possible basic explanation for the effects of thermal environment during growth. In conclusion, our results highlight the key role of thermal range amplitude on survival and on interactions with major metabolism‐regulating processes that have positive adaptive effects for organisms.
Highlights
Temperature variations diversely affect fish species, and while information is growing regarding the effects of thermal variation on aquatic systems, limited knowledge is available on impacts to the metabolic and physiological traits of fish
The mechanisms underlying the impacts of thermal environments are unknown, reports do exist for functional advantages in terms of physiology (Killen, 2014) and infection responses (Boltaña et al, 2013)
The present report is the first to provide evidence that the adaptive value of thermal behavior may depend on (1) temperature range amplitude, (2) the ability of the fish to choose a preferred temperature according to needs, and (3) the interaction thereof with metabolic mechanisms that, in turn, influence systemic regulatory systems during development
Summary
Temperature variations diversely affect fish species, and while information is growing regarding the effects of thermal variation on aquatic systems, limited knowledge is available on impacts to the metabolic and physiological traits of fish. Fish are exposed to spatial and temporal variations in temperature that significantly affect individual physiological traits (i.e., growth and metabolic condition), genetic structure (Bradbury et al, 2010), and/or survival (Houde, 2008). Atlantic salmon (Salmo salar), an anadromous fish species, live in streams, rivers, and open-ocean marine environments, experiencing spatial and temporal temperature fluctuations that influence survival and growth (Crozier, Zabel, & Hamlet, 2008). Farmed fish are more-or-less restricted to spatially constant temperature conditions within the containment unit This contrasts with wild fish, which are freely mobile and can choose different conditions according to physiological needs, the search for food, to escape predators, and other factors.
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