Evolutionary tuning of an adaptive behavior requires enhancement of the neuromast sensory system.

Cave animals are faced with the challenge of carrying out fundamental life processes in a completely dark environment. Evolution of behavioral changes could be one of the key steps that adapt these animals to the absence of light. Astyanax mexicanus is a teleost with sighted surface dwelling (surface fish) and blind cave dwelling (cavefish) forms. Cavefish, a descendant of surface fish ancestors, have evolved a suite of constructive traits including an increase in the number and diameter of superficial neuromasts (SN). Prior to our study, no clear relationships had been established between constructive traits and the evolution of behavior. The current results link SN enhancement to vibration attraction behavior (VAB), a behavioral shift that is beneficial for feeding in a dark environment. We discuss a possible scenario in which the evolution of VAB may be a key factor in the establishment and survival of cavefish ancestors in the dark cave environment.