EVOLUTIONARY DIFFERENCES IN NEUROPEPTIDE SIGNALING BETWEEN SURFACE AND CAVE MORPHOTYPES MAY CONTRIBUTE TO BEHAVIORAL DIFFERENCES IN A. MEXICANUS

The Mexican cavefish, Astyanax mexicanus, exists as a surface-dwelling form and multiple cave-dwelling populations that have converged on a series of behavioral and morphological changes. Previous studies identifying differences in hypothalamic neuropeptides in cave populations compared to surface fish call for further investigation of neuropeptides within the cavefish hypothalamus. Galanin is a hypothalamic neuropeptide that has been implicated in multiple behaviors across the teleost genus and has yet to be investigated in A. mexicanus. This study aimed to label and quantify galanin in the brain of 6 dpf Pachón cavefish and surface fish. The number of galanin-positive neurons in the hypothalamus is significantly decreased in Pachón cavefish compared to surface fish. These findings allow for further studies investigating the role of galanin in modulating behavior in A. mexicanus.