Phenotypic plasticity in visual opsin gene expression: a meta-analysis in teleost fish.

Phenotypic plasticity in visual opsin gene expression enables teleost fish to adjust their spectral sensitivity in response to environmental variability, yet the magnitude and drivers of this plasticity remain unresolved. We conducted a meta-analysis of 573 effect sizes from 36 studies to assess the prevalence and strength of opsin gene expression plasticity across teleost fishes, considering stimulus type (internal versus external) and timing of exposure (acute versus developmental). Plasticity of opsin gene expression was widespread and generally strong, with internal stimuli (e.g. hormonal changes) eliciting larger and more consistent responses than external stimuli (e.g. light conditions), particularly in the red-sensitive lws and UV-sensitive sws1 opsin genes. Phylogenetic analysis revealed no significant evolutionary constraints on opsin plasticity, suggesting that the capacity for visual system modulation is broadly distributed across teleost lineages. Our findings highlight the need for future studies to integrate behavioral, molecular and ecological data to evaluate the adaptive significance of opsin plasticity and its role in shaping visual performance under changing environmental conditions.