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. Read this story
