Reproductive acclimation to increased water temperature in a tropical reef fish

Abstract

Understanding the capacity of organisms to cope with projected global warming through acclimation and adaptation is critical to predicting their likely future persistence. While recent research has shown that developmental acclimation of metabolic attributes to ocean warming is possible, our understanding of the plasticity of key fitness-associated traits, such as reproductive performance, is lacking. We show that while the reproductive ability of a tropical reef fish is highly sensitive to increases in water temperature, reproductive capacity at +1.5°C above present-day was improved to match fish maintained at present-day temperatures when fish complete their development at the higher temperature. However, reproductive acclimation was not observed in fish reared at +3.0°C warmer than present-day, suggesting limitations to the acclimation possible within one generation. Surprisingly, the improvements seen in reproduction were not predicted by the oxygen- and capacity-limited thermal tolerance hypothesis. Specifically, pairs reared at +1.5°C, which showed the greatest capacity for reproductive acclimation, exhibited no acclimation of metabolic attributes. Conversely, pairs reared at +3.0°C, which exhibited acclimation in resting metabolic rate, demonstrated little capacity for reproductive acclimation. Our study suggests that understanding the acclimation capacity of reproductive performance will be critically important to predicting the impacts of climate change on biological systems.

Figure 1. Reproductive performance of treatment groups.

Mean (a) egg area, (b) clutch size and (c) reproductive output (mean egg area × clutch size) of Acanthochromis polyacanthus pairs maintained under the three temperature treatments. Values are mean ± SE. Letters represent significant differences between treatments (p<0.05).

Figure 2. Offspring characteristics at hatching depending on parental treatment groups.

Mean (a) standard length, (b) weight, (c) yolk area and (d) Fulton’s K condition of Acanthochromis polyacanthus offspring that resulted from pairs maintained under the three temperature treatments. Values are mean ± SE. Letters represent significant differences between treatments (p<0.05).

Figure 3. Offspring performance at 15 days post-hatching across all summer treatment temperatures.

Effect of parental treatment and juvenile rearing conditions on the standard length (SL), weight (W) and Fulton’s K condition index at 15 days post-hatching of Acanthochromis polyacanthus. Values are means ± SE.

Figure 4. Offspring performance at 30 days post-hatching across all summer treatment temperatures.

Effect of parental treatment and juvenile rearing conditions on the standard length (SL), weight (W) and Fulton’s K condition index at 30 days post-hatching of Acanthochromis polyacanthus. Values are means ± SE.