The body of priapulans (PRYE-uh-PUH-luhns) is divided into three parts: introvert (IN-troh-vert), trunk, and tail. The animals use a pair of muscles to pull the introvert completely into the trunk. Spines of various sizes and shapes cover the entire surface of the introvert. Inside the introvert is a muscular feeding tube armed with teeth.
The trunk houses the internal body organs, in particular the digestive system and reproductive organs. The body is filled with fluid that serves as a skeleton to support the body when the muscles of the body wall contract. When priapulans move, the fluid moves around in the body cavity and serves the functions of circulation, waste removal, and respiration. The tail is continuous with the body cavity of the trunk and may be used for respiration.
Animal Life ResourceJellyfish, Sponges, and Other Simple AnimalsPriapulans: Priapulida - Physical Characteristics, Behavior And Reproduction, No Common Name (priapulus Caudatus): Species Account - GEOGRAPHIC RANGE, HABITAT, DIET, PRIAPULANS AND PEOPLE, CONSERVATION STATUS