For more than 1 million years, independent cavefish populations that are geographically and hydrologically isolated from one another have evolved to include about 29 different populations. Among them, the tiny Mexican tetra, Astyanax mexicanus, which comprises river-dwelling surface fish and multiple independently evolved populations of blind cavefish. Many of the behaviors between these cavefish populations differ, suggesting widespread differences in brain structure and function. Although trait evolution in cavefish has been studied for more than a century, little is known about how their brains differ. Moreover, the differences in brain activity have never been explored.
A groundbreaking study by neuroscientists at Florida Atlantic University’s Charles E. Schmidt College of Science and Harriet L. Wilkes Honors College in collaboration with Bar-Ilan University, Ramat-Gan in Israel, is the first to identify large-scale differences between surface fish and cavefish populations of A. mexicanus, as well as between different populations of cavefish. Researchers extracted 18 anatomical regions across the entire brain and measured changes in neural activity across these regions. Whole-brain atlases generated from this study represent a comparative brain-wide study of intraspecies variation in a vertebrate model and provide a resource for studying the neural basis underlying behavioral evolution.
“Cavefish have evolved numerous behavioral changes, including sleep loss, reduced social behaviors, widespread changes in sensory processing, and alterations in foraging behavior,” said Alex C. Keene, Ph.D., lead author and an associate professor of biological sciences in FAU’s Charles E. Schmidt College of Science. “Despite the long-standing focus on characterizing differences in behavior and morphology between cave populations, unexpectedly little is known about the brain anatomy and neural circuits associated with these behavioral changes in cave populations.”
