Enteric neural crest development in Astyanax mexicanus surface fish and cavefish

The enteric nervous system (ENS) regulates gastrointestinal (GI) functions such as secretion, blood flow, and motility, yet how its structure and function evolve with dietary adaptations remains unclear. Astyanax mexicanus , a teleost fish with surface and cave morphotypes, offers a model to explore these changes; cavefish exhibit altered GI motility and transit that may help them adapt to their unique diet. We compared early ENS development in surface fish and cavefish, tracking enteric neural crest cell (ENCC) migration and differentiation using phox2bb and HuC/D markers. We found that ENCCs reach the gut by 36 hours post-fertilization (hpf) in both morphotypes but migrate and differentiate more rapidly along the gut tube in cavefish. To explore the genetic basis of this difference, we used available genomic datasets to compare the predicted peptide sequences of genes important for ENS development in other species and identified mutations that could impact protein function, for example in the endothelin signaling genes important for ENCC migration and differentiation. We specifically examined the expression of endothelin-3 (edn3) and endothelin receptor-b (ednrb) during ENCC migration and found that the localization of edn3 , but not ednrb , is consistent with a role in ENS development. Overall, our findings position A. mexicanus as a model for studying evolution of ENS development.