Subterranean Fishes of the World

5613

2022

AIM 2022

20

When subjected to similar environmental conditions, organisms often repeatedly evolve similar traits. Identifying and functionally verifying the genetic variants underlying these traits is an important step in understanding how and why these traits repeatedly evolve. In recent years, genetic mapping approaches have been used to uncover the genetic architecture underlying the evolution of many traits. While these approaches have identified many loci and candidate genes implicated in trait evolution, functionally verifying the role of these genes in natural populations has remained challenging. To address this, we have established genome editing approaches in A. mexicanus, a single species of fish existing in surface and cave forms, allowing us to directly assess the role of candidate genes for complex traits. One trait that is commonly observed in cave organisms is loss of melanin pigmentation, or albinism. Interestingly, in A. mexicanus, multiple cave populations exhibit albinism due to mutations in the same gene, oculocutaneous albinism II (oca2). To determine if oca2 plays a role in other cave evolved traits, we used CRISPRCas9 genome editing to obtain an in-depth analysis of the effects of mutations in the oca2 gene on cavefish evolution. We have found that in addition to albinism, mutations in oca2 alter a number of cave-evolved behaviors, including how fish capture prey. Surface fish harboring mutations in the oca2 gene strike prey at wider angles than wild-type siblings. This behavior is similar to cavefish behavior, as well as surface fish behavior in dark conditions. However, this altered prey capture behavior is not dependent on the lateral line, suggesting it is not due to a shift towards lateral line dependent hunting behavior. Together, these results suggest that mutations in oca2 alter how fish hunt and may shed light on how albinism has evolved in this species.

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