A conserved teleost motor asymmetry requires evolutionary retention of vision

Behavioral laterality is a prominent feature in Bilateria, where a motor function is performed with a leftward or rightward preference. Underlying these lateralized or asymmetric behaviors is thought to be hemispheric specializations that improve behavioral performance. Despite the prevalence of behavioral lateralization, our understanding of the neural and molecular substrates instructing its underlying neural mechanisms are limited. Moreover, how functional lateralization is selected for or modulated throughout evolution is poorly understood. Comparative approaches are a powerful strategy for addressing fundamental biological questions at individual, population, and evolutionary scales. Yet, a major obstacle for employing comparative analysis to address laterality has been the lack of a conserved lateralized behavior in lab assessable species. Previously, we described a robust visuomotor asymmetry in larval zebrafish that is a motor element of search pattern behavior. In this study, we compare search pattern behavior and motor asymmetry across a range of lab-accessible larval teleost species. We show that motor patterns underlying search behavior are variable throughout teleost evolution while behavioral asymmetry is conserved across four phylogenetic Orders of sighted larval teleost, yet not naturally blind cavefish. Our data demonstrates that motor asymmetry in larval teleosts is a conserved and tractable lateralized behavior that can be modulated by natural selection in a vision dependent manner. Our findings reveal that motor asymmetry is a deeply conserved and tractable behavioral phenotype in larval teleosts, and one that can be shaped by natural selection. This establishes larval teleosts as a powerful system for dissecting the neural architecture and evolutionary forces that govern behavioral lateralization, bridging the gap between mechanism and adaptation