Figure 1.

(a) Conceptual diagram: predicted responses of temperature-dependent selection on and intergenerational plasticity of embryo metabolic rates (MR) at cool and hot offspring temperatures. We hypothesise that hot offspring temperatures will select for lower metabolic rates, while selection at the cool offspring temperature will be relatively relaxed (positive but no significant correlation between fitness and metabolic rate shown). If intergenerational plasticity aligns with selection when environments across generations match, then similar trends in the direction and strength of selection should be observed. We therefore predict that parents in the warm environment (pink) will produce offspring with lower metabolic rates (smaller curved arrows) compared to parents from the cool temperature (blue), and that this will be correlated with development time and growth rates, with fitness benefits for offspring. (b) Experimental design: parents were held under one of four treatment combinations: 24°C or 30°C and low or high feeding frequency, then bred to produce offspring that were reared at either 24°C or 30°C. Embryo size (diameter, area, mass) and yolk area were measured at 1–4 h post fertilization (hpf), and metabolic rates (measured as rate of oxygen consumption) measured at three stages: 25% of embryonic development (MR_embryo), 1–4 h post-hatching (hph; MR_hatch), and 1 week post-hatching (1 wph; MR_larva). Offspring were then monitored for survival up to two weeks post-hatching.