Link between coloration, behavior and gene expression in the brain suggests divergent camouflage strategies in a coral reef fish species pair.. Hamlet Camouflage

Camouflage - the ability to blend in with the environment - is a critical survival strategy that helps to escape predation and increase the likelihood of successful hunting. Depending on a species’ environment and physical traits, camouflage can take different forms including background matching and disruptive coloration. Since different forms of camouflage are associated with different selective pressures, divergence in its associated features, such as body coloration and behavior, can alternate evolutionary trajectories and drive speciation. Here, we test whether distinct color patterns in closely related species are associated with behavioral differences in predator avoidance strategies. Combining a set of field and laboratory experiments, we found that disruptive coloration was associated with a flight response, while black coloration — background matching to dark holes — was linked to hiding as a means of avoiding predation. Other non-predator related behaviors, such as sociability and activity, did not differ between the species. Interestingly, the behavioral difference between the species was also reflected in the transcriptome profile of their brains. While the brain region incorporating the mesolimbic reward system and social decision-making axis did not show differential gene expression between the species, the optic tectum (OT, linked to visual perception) and diencephalon (DIENC, e.g. hormone regulation) showed clear signs of differential expression, notably in locomotion regulation (OT), immune response and signaling genes (OT, DIENC). Considering that predator-prey interactions are critical for survival, effective predator avoidance strategies through phenotypic and behavioral adaptations are expected to represent a major ecological and evolutionary driver.