The forebrain of the blind cavefish Astyanax mexicanus as a model system to link developmental evolution of neural circuits and of animal behavior – ASTYCO

The goal of this project is to link variations of early forebrain morphogenesis in closely-related species with their consequences on the development of neuronal networks, and with the behaviors they govern. The project is based on a comparative and functional approach and will analyze neuro-developmental and behavioral variations that have been selected during adaptation of populations to their environment.
To this end we will use an original animal model, the fish Astyanax mexicanus (closely-related to zebrafish). Within the same species, Astyanax presents several populations of river-dwelling surface fish and blind cave-living fish which differ by their morphology, their physiology, and their behavior. The modulation of morphogen signals from the Hedgehog and Fgf8 signaling centers during early embryogenesis is in great part responsible for the anatomical differences observed between cavefish and surface fish, including the loss of eyes.

We will analyze the Hedgehog- and Fgf8-dependent mechanisms which govern the morphogenesis of the eyes, the olfactory system, and the hypothalamus, the three forebrain regions which differ the most between cavefish and surface fish embryos and larvae.

We will analyze how the developmental differences in the establishment of olfactory and hypothalamic circuits condition the variations in feeding and social behavior described between the two populations.

Finally, we will test whether the modifications in neuronal networks and their behavioral outcomes are adaptive. This is a necessary condition to support our hypothesis that the loss of eyes in cavefish is a secondary consequence of natural selection for beneficial traits involved in adaptation to life in darkness.