Urodele amphibian newt bridges the missing link in evo-devo of the pancreas.

Background: The pancreas exhibits diverse structures and roles across vertebrates. The pancreas has evolved to include both endocrine and exocrine cells, a change that occurred during the transition from fish to amphibian. This event emphasizes the evolutionary significance of amphibians. However, research has focused predominantly on anuran amphibians, with urodeles, such as newts, remaining underexplored. In this study, we investigated the development of the pancreas using Pleurodeles waltl as a model species of urodele.

Results: The newt pancreas consists of a single organ with exocrine tissue characterized by acinar structures and endocrine tissue forming islets. Notably, the newt possesses unique pancreas-like tissues on their intestines. We found that disruption of the newt Pancreatic and Duodenal Homeobox (Pdx) 1 gene resulted in an underdeveloped pancreas. Conversely, disruption of the Pdx2 paralog in newt had no significant impact on pancreatic development.

Conclusion: The newt pancreas shows a morphology similar to that of the mammalian pancreas, which includes both exocrine and endocrine tissues. These results highlight the intermediate evolutionary position of the newt in the context of the evolution of pancreatic development. Our findings indicate that characterization of the newt pancreas will be crucial for understanding the evolutionary progression of pancreatic function in vertebrates.