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Water as a driver of evolution: the example of aquatic snakes.
Animal-environment interactions are determinant in driving the evolution of phenotypic variation. Most aquatic animals have developed adaptations to overcome the physical constraints inherent to an aquatic lifestyle. The aim of this project is to evaluate the role of water as a potential driver of evolution by focusing on morphological and behavioral convergence during prey capture in water. Snakes are a good model as an aquatic life-style has originated independently in different genera. However, aquatic snakes did not develop a suction feeding system in contrast to most aquatic vertebrates. Prey-capture under water is constrained by the physical properties of the fluid and thus morphological and/or behavioral convergence is expected. By comparing the head shapes of different species, we highlighted a morphological convergence of aquatic snakes related with aquatic foraging. From this analysis, we characterized a shape that corresponds to aquatic species and tried to validate the hypothesis of a hydrodynamic advantage related with this shape by using experimental fluid mechanics approaches. We quantified the physical constraints involved in underwater prey-capture and we assessed how shape differences impact the hydrodynamic forces. We have demonstrated that aquatic snakes head shape is, at least partly, optimized to perform a frontal strike.