Analysis of stress responses in Astyanax larvae reveals heterogeneity among different populations

Abstract

Stress responses are conserved physiological and behavioral outcomes as a result of facing potentially harmful stimuli, yet in pathological states, stress becomes debilitating. Stress responses vary considerably throughout the animal kingdom, but how these responses are shaped evolutionarily is unknown. The Mexican cavefish has emerged as a powerful system for examining genetic principles underlying behavioral evolution. Here, we demonstrate that cave Astyanax have reduced behavioral and physiological measures of stress when examined at larval stages. We also find increased expression of the glucocorticoid receptor, a repressible element of the neuroendocrine stress pathway. Additionally, we examine stress in three different cave populations, and find that some, but not all, show reduced stress measures. Together, these results reveal a mechanistic system by which cave-dwelling fish reduced stress, presumably to compensate for a predator poor environment. Research HighlightO_LICavefish populations of A. mexicanus have reduced stress relative to surface conspecific at larval stages C_LIO_LIWe show that a glucocorticoid receptor, a negative regulator of the neuroendocrine stress axis, is upregulated in stress-resistant cavefish C_LIO_LIThere exists much ontological heterogeneity between different cavefish populations. C_LI