Flatworms

Flatworms, also known as Platyhelminthes, are a group of basal bilaterian animals. Flatworms are unique among the bilaterian animals since they are acoelomate, meaning they lack a body cavity. Instead, they have a simple body plan with a three-layered body structure, an gut, and an outer epidermis. Flatworms are important to the fields of parasitology and evolutionary biology as they are typically the simplest animals with a bilateral body plan and a nervous system. They also provide important insights into the evolution of the development of bilateral animals. Flatworms are used in laboratory studies, since they are able to regenerate lost body parts. There are many species of flatworms and they can be found in many different habitats, from marine and freshwater environments to land-dwelling species.