Light environment change induces differential expression of guppy opsins in a multi-generational evolution experiment

Light environments critically impact species that rely on vision to survive and reproduce. Animal visual systems must accommodate changes in light that occur from minutes to years, yet we do not know how they respond to divergent spectral changes over longer time scales. Here we used a laboratory experiment where replicate guppy populations were kept different light environments for up to 8-12 generations to explore possible differences in the expression levels of nine guppy opsin genes. Previous evidence for opsin expression-light environment ‘tuning’ has been either correlative or focused exclusively on the relationship between the light environment and opsin expression over one or two generations. In our multi-generation experiment, the relative expression levels of nine different opsin genes responded differently to light environment changes: some did not respond, while others differed due to phenotypic plasticity. Moreover for LWS-1 we found that, while we observed a wide range of plastic responses under different light conditions, common plastic responses occurred only after multigenerational exposure to different light environments. Taken together this suggests that opsin expression plasticity plays an important role in light environment ‘tuning’ in different light environments and, in turn, has important implications for both visual system function and evolution.