Mutations in the albinism geneoca2alter vision-dependent prey capture behavior in the Mexican tetra

Abstract

Understanding the phenotypic consequences of naturally occurring genetic changes, as well as their impact on fitness, is fundamental to understanding how organisms adapt to an environment. This is critical when genetic variants have pleiotropic effects, as determining how each phenotype impacted by a gene contributes to fitness is essential to understand how and why traits have evolved. A striking example of a pleiotropic gene contributing to trait evolution is theoca2gene, coding mutations in which underlie albinism and reductions of sleep in the blind Mexican cavefish,Astyanax mexicanus. Here, we characterize the effects of mutations in theoca2gene on larval prey capture. We find that when conspecific surface fish with engineered mutations in theoca2allele are hunting, they use cave-like, wide angle strikes to capture prey. However, unlike cavefish or surface fish in the dark, which rely on lateral line mediated hunting,oca2mutant surface fish use vision when striking at prey from wide angles. Finally, we find that whileoca2mutant surface fish do not outcompete pigmented surface siblings in the dark, pigmented fish outcompete albino fish in the light. This raises the possibility that albinism is detrimental to larval feeding in a surface-like lighted environment, but does not have negative consequences for fish in cave-like, dark environments. Together, these results demonstrate thatoca2plays a role in larval feeding behavior inA. mexicanus. Further, they expand our understanding of the pleiotropic phenotypic consequences ofoca2in cavefish evolution.