Effects of warming rate, acclimation temperature and ontogeny on the critical thermal maximum of temperate marine fish larvae

Marine heatwaves, which are increasing in frequency, duration and intensity owing to climate change, are an imminent threat to marine ecosystems. On coral reefs, heatwave conditions often coincide with periods of peak recruitment of juvenile fishes and exposure to elevated temperature may affect their development. However, whether differences in the duration of high temperature exposure have effects on individual performance is unknown. We exposed juvenile spiny damselfish, Acanthochromis polyacanthus, to increasing lengths of time (3, 7, 30 and 108 days post-hatching) of elevated temperature (+2°C). After 108 days, we measured escape performance at present-day control and elevated temperatures, standard length, mass and critical thermal maximum. Using a Bayesian approach, we show that 30 days or more exposure to +2°C leads to improved escape performance, irrespective of performance temperature, possibly owing to developmental effects of high temperature on muscle development and/or anaerobic metabolism. Continued exposure to elevated temperature for 108 days caused a reduction in body size compared with the control, but not in fish exposed to high temperature for 30 days or less. By contrast, exposure to elevated temperatures for any length of time had no effect on critical thermal maximum, which, combined with previous work, suggests a short-term physiological constraint of ∼37°C in this species. Our study shows that extended exposure to increased temperature can affect the development of juvenile fishes, with potential immediate and future consequences for individual performance.

Section: Discussionmentioning

confidence: 56%

Developmental effects of heatwave conditions on the early life stages of a coral reef fish

Spinks

Munday

2019

“…First, we experimentally induced among-individual variation in T imm through acclimation to different temperatures (e.g. Cambronero et al, 2017 ; Moyano et al, 2017 ). Second, when exposed to 37°C, we filmed the experimental individuals, up to and including the point when they lost swimming function (i.e.…”

Section: Methodsmentioning

confidence: 99%

“…The moving median requires the parameter w , which specifies the window width, the number of observations in a time series over which each successive iteration of the moving median is calculated. Given that an individual's T imm should be positively affected by warm acclimation temperatures ( Cambronero et al, 2017 ; Moyano et al, 2017 ) and should be lower in larger, older individuals ( Brans et al, 2017 ; Messmer et al, 2017 ), the optimal choice of values for V thresh and w should be the combination that maximises the amount of variation in T imm that can be described by acclimation treatment (17 and 22°C), when also statistically controlling for the variation in body size that was present both among and within each acclimation treatment (see ).…”

Section: Methodsmentioning

confidence: 99%

Automated measurement of upper thermal limits in small aquatic animals

Burton

Zeis

Einum

2018

We present a method for automating the measurement of upper thermal limits in small aquatic organisms. Upper thermal limits are frequently defined by the cessation of movement at high temperature, with measurement being performed by manual observation. Consequently, estimates of upper thermal limits may be subject to error and bias, both within and among observers. Our method utilises video-based tracking software to record the movement of individuals when exposed to high, lethal temperatures. We develop an algorithm in the R computing language that can objectively identify the loss of locomotory function from tracking data. Using independent experimental data, we validate our approach by demonstrating the expected response in upper thermal limits to acclimation temperature.

“…Owing to anthropogenically driven climate change, the numbers of extreme hot or cold days could increase, which is expected to have a particularly strong impact on ectothermic animals (Buckley et al, 2012;Li et al, 2015). As a key environmental factor in mediating homeostasis in ectotherms, ambient temperature not only affects factors associated with the living environment, such as water distribution (Buckley et al, 2012), germ transmission (Raffel et al, 2012) and the dissolution of toxic substances (Guo et al, 2018), but also acts as a stressor to organisms and affects normal larval development (Moyano et al, 2017), immune function (Maniero and Carey, 1997), tissue metabolism (Costanzo and Lee, 2008;Sinclair et al, 2012) and other physiological functions.…”

Section: Introductionmentioning

confidence: 99%

Effects of both cold and heat stresses on the liver of giant spiny frog Quasipaa spinosa: stress response and histological changes

Liu

et al. 2018

Ambient temperature-associated stress can affect normal physiological functions in ectotherms. To assess the effects of cold or heat stress on amphibians, giant spiny frogs () were acclimated at 22°C followed by exposure to 5°C or 30°C for 0, 3, 6, 12, 24 and 48 h, respectively. Histological alterations, apoptotic index, generation of mitochondrial reactive oxygen species (ROS), antioxidant activity indices and stress-response gene expression in frog livers were subsequently determined. Results showed that many fat droplets appeared after 12 h of heat stress and the percentage of melanomacrophage centres significantly changed after 48 h at both stress conditions. Furthermore, the mitochondrial ROS levels were elevated in a time-dependent manner up to 6 h and 12 h in the cold and heat stress groups, respectively. The activities of superoxide dismutase, glutathione peroxidase and catalase were successively increased with increasing periods of cold or heat exposure, and their gene expression levels showed similar changes in both stress conditions. Most tested heat shock protein (HSP) genes were sensitive to temperature exposure, and the expression profiles of most apoptosis-related genes was significantly upregulated at 3 and 48 h under cold and heat stress, respectively. Apoptotic index at 48 h under cold stress was significantly higher than that under heat stress. Notably, lipid droplets, , and might be suitable bioindicators of heat stress. The results of these alterations at physiological, biochemical and molecular levels might contribute to a better understanding of the stress response of, and perhaps amphibians more generally, under thermal stress.