A protocol for whole-brain Ca²⁺ imaging in Astyanax mexicanus, a model of comparative evolution

In this protocol, we describe a comparative approach to study the evolution of brain function in the Mexican tetra, Astyanax mexicanus. We developed surface fish and two independent populations of cavefish with pan-neuronal expression of the Ca²⁺ sensor GCaMP6s. We describe a methodology to prepare samples and image activity across the optic tectum and olfactory bulb.