Mutations in the albinism gene oca2 alter 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. Here, we characterize the effects of mutations in the oca2 gene, coding mutations in which underlie albinism and reductions of sleep in the blind Mexican cavefish Astyanax mexicanus, on larval prey capture. We find that when surface A. mexicanus with engineered mutations in oca2 are hunting, they use cave-like, wide angle strikes to capture prey. However, unlike cavefish or surface fish in the dark, which utilize the lateral line when hunting, oca2 mutant (oca2Δ2bp/Δ2bp) surface fish can use vision when striking at prey from wide angles. We find that when raised under lighted conditions, pigmented surface fish outcompete albino oca2Δ2bp/Δ2bp surface fish when hunting in lighted conditions. In contrast, when surface fish are reared in darkness, oca2Δ2bp/Δ2bp surface fish outcompete their wild type siblings in the dark. This raises the possibility that albinism is detrimental to larval feeding in a surface-like lighted environment, but may confer an advantage to fish in cave-like, dark environments. Together, these results demonstrate that oca2 plays a role in larval feeding behavior in A. mexicanus, and expand our understanding of the pleiotropic phenotypic consequences of oca2 in cavefish evolution.