Advances in understanding the evolution of stomach loss in agastric fishes

Living beings can evolve to lose biological structures due to potential survival benefits from such losses. For example, certain groups of ray-finned fishes show such regressive evolution—medakas, minnows, puffera, and wrasses do not have a stomach in the gastrointestinal tract, making them agastric or stomachless fishes. However, the specific evolutionary mechanisms underlying the evolution of agastric fishes remain unclear.