Abstract
Recent studies have shown that elevated CO2 can affect the behaviour of larval and juvenile fishes. In particular, behavioural lateralization, an expression of brain functional asymmetries, is affected by elevated CO2 in both coral reef and temperate fishes. However, the potentially interacting effects of rising temperatures and CO2 on lateralization are unknown. Here, we tested the combined effect of near-future elevated-CO2 concentrations (930 µatm) and temperature variation on behavioural lateralization of a marine damselfish, Pomacentrus wardi. Individuals exposed to one of four treatments (two CO2 levels and two temperatures) were observed in a detour test where they made repeated decisions about turning left or right. Individuals exposed to current CO2 and ambient temperature levels showed a significant right-turning bias at the population level. This biased was reversed (i.e. to the left side) in fish exposed to the elevated-CO2 treatment. Increased temperature attenuated this effect, resulting in lower values of relative lateralization. Consequently, rising temperature and elevated CO2 may have different and interactive effects on behavioural lateralization and therefore future studies on the effect of climate change on brain functions need to consider both these critical variables in order to assess the potential consequences for the ecological interactions of marine fishes.
Highlights
The amount of CO2 dissolved in the ocean and the average temperature of the ocean are rising as a result of increasing concentrations of atmospheric CO2 [1]
Elevated CO2 influenced the direction of lateralization; individuals from Control-CO2/Control-Temperature and Control-CO2/Elevated-Temperature had a significant preference for right turns (LR = 26.964.04 and 9.564.43, respectively), whereas individuals from Elevated-CO2/Control-Temperature had a significance preference for left turns (LR = 221.064.80)
Our work is the first one to test the effect of exposure to elevated CO2 levels in a species that is lateralized at the population level
Summary
The amount of CO2 dissolved in the ocean and the average temperature of the ocean are rising as a result of increasing concentrations of atmospheric CO2 [1]. Recent work has shown that increased CO2 levels predicted to occur in the ocean by the end of this century can have negative effects on a number of behavioural attributes of marine fishes, such as anti-predator responses [2], [3], sensory performance [4], [5] and lateralization [6], [7]. In fishes and other animals, individuals may show a tendency to turn more often in one direction in a T-maze (detour test), or to use the left or right limb more often when facing a specific task [14] This behavioural lateralization is an expression of brain asymmetry [14], [15]. In the present study we test the interactive effects of elevated CO2 and temperature variation on individual and population-level lateralization in a coral reef damselfish
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