Phenotypic and molecular consequences of stepwise temperature increase across generations in a coral reef fish

Abstract

Global warming will have far‐reaching consequences for marine species over coming decades, yet the magnitude of these effects may depend on the rate of warming across generations. Recent experiments show coral reef fishes can compensate the metabolic challenges of elevated temperature when warm conditions are maintained across generations. However, the effects of a gradual temperature increase across generations remain unknown. In the present study, we analysed metabolic and molecular traits in the damselfish Acanthochromis polyacanthus that were exposed to +1.5°C in the first generation and +3.0°C in the second (Step +3.0°C). This treatment of stepwise warming was compared to fish reared at current‐day temperatures (Control), second‐generation fish of control parents reared at +3.0°C (Developmental +3.0°C) and fish exposed to elevated temperatures for two generations (Transgenerational +1.5°C and Transgenerational +3.0°C). Hepatosomatic index, oxygen consumption and liver gene expression were compared in second‐generation fish of the multiple treatments. Hepatosomatic index increased in fish that developed at +3.0°C, regardless of the parental temperature. Routine oxygen consumption of Step +3.0°C fish was significantly higher than Control; however, their aerobic scope recovered to the same level as Control fish. Step +3.0°C fish exhibited significant upregulation of genes related to mitochondrial activity and energy production, which could be associated with their increased metabolic rates. These results indicate that restoration of aerobic scope is possible when fish experience gradual thermal increase across multiple generations, but the metabolic and molecular responses are different from fish reared at the same elevated thermal conditions in successive generations.

Species-specific molecular responses of wild coral reef fishes during a marine heatwave

“…Unfortunately, obtaining a "control" year was logistically impossible because we could not predict the heatwave conditions sufficiently in advance, and due to an already very ambitious sampling scheme for species with no previous genomic resources (with the exception of A. polyacanthus). Despite these limitations, the functions of genes that showed expression changes over the duration of the heatwave concur with previous laboratory experiments on A. polyacanthus, one of the most studied tropical marine fish species in the context of global change (19,20).…”

“…When temperatures are too high, the cardiorespiratory system is no longer able to fulfill additional oxygen demands for aerobic activities, leading to a reduction in aerobic performance (15,16), alteration of growth rates (17), and reduction in swimming speeds (18). Previous studies focusing on gene expression of captive fishes have shown that increased oxygen demands at higher temperatures can lead to activation of genes related to mitochondrial activity, the electron-transport chain, fatty acid metabolism, and cellular stress response (19,20). Furthermore, reproductive hormones can be affected by warmer conditions, leading to changes in reproductive behavior and declines in reproductive output (21).…”

Beyond buying time: the role of plasticity in phenotypic adaptation to rapid environmental change

“…After all, the genome and, more especially, its regulation must be highly dynamic to allow for plasticity to occur and we need to learn more about both genetic and epigenetic mechanisms to understand how climate stressors can influence and shape genomes, transcriptomes and the epigenome, in particular, across generations. In recent years, considerable effort has been expended on trying to understand the molecular, genomic and epigenomic mechanisms underlying responses to climate stressors across a variety of species and populations, including fish [72][73][74][75][76], corals [77,78], other invertebrates [79 -81] and plants (review: [82]). In the process, we have substantially increased our knowledge of the molecular mechanisms underlying plasticity (e.g.…”

Probing SWATH‐MS as a tool for proteome level quantification in a nonmodel fish

“…These included proteins related to the heat shock response (HSP), Abbreviations: CV, coefficients of variance; DDA, data-dependent acquisition; DIA, Data-independent acquisition. a well-documented expression change seen in fish exposed to elevated temperatures (Basu et al, 2002), cytochrome related genes involved in oxidative stress and several other previously identified stress response genes in marine fish representing protein degradation and cell death. In Figure 4, we see the combined DDA libraries provided the least identifications of the complex cellular stress response identified by the other libraries.…”