Abstract
ABSTRACTThermal acclimation causes the heart of some fish species to undergo significant remodelling. This includes changes in electrical activity, energy utilization and structural properties at the gross and molecular level of organization. The purpose of this Review is to summarize the current state of knowledge of temperature-induced structural remodelling in the fish ventricle across different levels of biological organization, and to examine how such changes result in the modification of the functional properties of the heart. The structural remodelling response is thought to be responsible for changes in cardiac stiffness, the Ca2+ sensitivity of force generation and the rate of force generation by the heart. Such changes to both active and passive properties help to compensate for the loss of cardiac function caused by a decrease in physiological temperature. Hence, temperature-induced cardiac remodelling is common in fish that remain active following seasonal decreases in temperature. This Review is organized around the ventricular phases of the cardiac cycle – specifically diastolic filling, isovolumic pressure generation and ejection – so that the consequences of remodelling can be fully described. We also compare the thermal acclimation-associated modifications of the fish ventricle with those seen in the mammalian ventricle in response to cardiac pathologies and exercise. Finally, we consider how the plasticity of the fish heart may be relevant to survival in a climate change context, where seasonal temperature changes could become more extreme and variable.
Highlights
Ectothermic animals living in temperate environments can experience significant, long-term changes in ambient temperature
The ability of some fish to remodel their heart in response to changes in environmental temperature has ecological consequences, as it enables them to remain active over a wide range of environmental temperatures
Such plasticity may improve their ability to maintain cardiac function as average seasonal temperatures increase with global climate change
Summary
Ectothermic animals living in temperate environments can experience significant, long-term changes in ambient temperature. These seasonal fluctuations influence every level of biological function as a result of the universal effect of temperature on molecular interactions. Biochemical, physiological and biomechanical processes are all affected by changes in temperature. A number of ectothermic species, including some fish, remain active across the seasons. These fish species include salmonids such as rainbow trout (Oncorhynchus mykiss), which, depending on the strain, can remain active at temperatures ranging from ∼4 to 24°C (Anttila et al, 2014; Elliott and Elliott, 2010; Rodnick et al, 2004). Members of the minnow family, such as the zebrafish (Danio rerio), have broad thermal tolerances in
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