SG: Uncovering the contributions of albinism to the evolution of the Mexican cavefish

When different organisms live in similar environments, the same traits can evolve in multiple, independent populations. One fascinating example of this is the reduction or loss of pigmentation in many different cave organisms. Despite how common this pattern is in wild populations, why cave organisms lose pigmentation is not well understood.

This research will study the role of pigmentation loss in the evolution of Mexican cavefish. To do so, the project will examine the relationship between pigmentation, levels of neurotransmitters in the brain, and behavioral changes that may be beneficial to animals living underground. The broader impacts of this project take advantage of the cavefish system to increase access to science education.

Teachers will work with the researchers to develop new units on cavefish biology to take back to their classrooms. Additionally, the researchers will create an undergraduate class that will allow students to get authentic research experiences. Finally, undergraduates and graduate students will be hired to participate in the research.

This project aims to understand the effects of pigmentation-reducing mutations on behavioral traits. Evidence suggests that mutations in the oca2 gene underlie albinism. Additionally, the mutations may impact levels of sleep-regulating neurotransmitters, raising the possibility that albinism is beneficial by reducing sleep time and promoting foraging in the nutrient-poor cave environment.

To test this hypothesis, the research team will focus on A. mexicanus. Some advantages of this system include the existence of multiple, independently evolved cave populations and the ability to hybridize cave and surface fish. Specifically, this project has three aims.

First, the researchers will measure levels of three specific neurotransmitters (dopamine, epinephrine, norepinephrine) in multiple populations of fish. Those populations include: 1) surface fish, 2) albino (oca2-mutant), 3) non-albino cavefish, and 4) oca2-mutant surface fish. Measuring neurotransmitter levels in the different fish populations will allow the researchers to determine if enhanced neurotransmitter levels are a general property of cavefish with reduced pigmentation.

For the second aim, sleep will be measured in wild-type and oca2-mutant surface fish to determine the role of oca2 in a potentially fitness-related trait. Finally, the researchers will generate hybrids by crossing individuals from cave populations and surface populations. Sleep, pigmentation and neurotransmitter levels will be measured in these hybrid fish to determine the genetic relationship between these traits.

Thus, this project will provide new insight into the role of albinism in a cave environment. Further, it will shed light on fundamental principles underlying evolution in response to colonization of a novel environment.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.