Shifting from Right to Left: The Combined Effect of Elevated CO2 and Temperature on Behavioural Lateralization in a Coral Reef Fish

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.

Severe hypoxia impairs lateralization in a marine teleost fish

“…Hence, exposure to hypoxia might cause right-lateralized individuals to become leftlateralized (see peak at LR=−60), resulting in the loss of the original side bias in the whole population while maintaining a similar individual-level lateralization as in normoxia. A similar effect was found in a coral reef fish, where exposure to elevated CO 2 levels affected population-level but not individual-level lateralization (Domenici et al, 2014). In contrast, studies on other species reported an effect of exposure to elevated CO 2 in individual-level but not in population-level lateralization (e.g.…”

“…Some evidence and theoretical work suggests that stressful situations could cause a shift of information processing between the two hemispheres (i.e. from left to right control) (Rogers, 2010;Domenici et al, 2014). In line with Rogers (Rogers, 2010), it is possible that the stress due to hypoxia caused treated subjects to increase right-hemisphere control.…”

“…Moreover, in coastal areas very often fish are simultaneously exposed to other stressors in addition to hypoxia, such as increased temperature, elevated CO 2 or ammonia. Some of these stressors are known to affect lateralization (temperature and elevated CO 2 ) (Domenici et al, 2014), hence they could potentially interact with hypoxia to alter behavioural lateralization. Therefore, broader investigations on the synergistic effect of different environmental factors on a wide range of species would be of great value to understand the underlying physiological processes and ecological implications of the increasing worldwide incidence of hypoxic zones.…”

“…Subsequently, by using a pair of small fish nets, the subject was gently conducted up to half of the runway, in order to encourage it to swim toward the barrier. For each subject the procedure was repeated ten times alternating between the two symmetrical ends of the runway (Domenici et al, 2014). The direction of turns in front of the barrier was recorded.…”

Brain lateralization involved in visual recognition of conspecifics in coral reef fish at recruitment

“…Indeed, nocturnally active fish species that spend less than 30 days in the pelagic environment before settling have a larger optic tectum and telencephalon than diurnal fish species that spend less than 15 days in the ocean . Additionally, behavioural lateralization in coral reef fish larvae is impaired by ocean acidification (Domenici et al, 2014Nilsson et al, 2012). Few studies have explored whether lateralization could vary across the development of an individual (Concha, Bianco, & Wilson, 2012;Rogers et al, 2013;Skiba, Diekamp, & Güntürkün, 2002).…”