Subterranean Fishes of the World

4307

2019

AIM 2019

58

Stress responses are evolutionarily conserved reactions, which protect animals from potential threats. Although stress behaviors are found in all animals, the timing and degree of stress to a given aversive cue varies among animals of different species. However, little is known about how changes to brain structure and function lead to evolutionarily derived differences in stress behaviors. The Mexican blind cavefish is well suited to address how this question. We demonstrate that cavefish show dramatically diminished stress responses compared to their eyed, surface dwelling conspecifics. The differences in behaviors are not mediated by visual cues, as adult surface recorded in darkness still show enhanced stress compared to cavefish, also recorded in darkness. We also demonstrate that multiple, independently evolved cave fish population have all converged on a reduced stress phenotype, suggesting diminished stress may be generalizable to these cavefish. To explore how whole-brain circuits that underlie stress may differ between surface and cave forms, we have also looked at stress in larvae. Like adults, larval cavefish have reduced stress, measured by duration of freezing following a mild electric shock. Surface x cave hybrids have variable stress behaviors that span the surface and cave distributions. As a complement to in vivo two-photon whole-brain calcium imaging, we are using immunolabeling methods for capturing neural activity to define regions of the cave and surface brain that underlie stress, and examining how these whole-brain patterns of neural activity differ between surface and cave. Taken together, our data show that there are robust evolutionarily derived differences in stress between surface and cavefish, and implicate different regions of the brain as leading to these difference. The model will allow us to examine how evolution can impact the brain, and lead to stress behaviors well suited for the given ecological setting.

1

Astyanax Interrnational Meeting