Parapodia are paired, lateral extensions found on the bodies of certain marine organisms, particularly in the phylum Annelida, which includes segmented worms. These structures serve various functions, including locomotion and respiration. In many species, parapodia are equipped with bristles called setae that help the organism move through water or burrow into sediment. In addition to aiding movement, parapodia can also increase the surface area for gas exchange, allowing the organism to breathe more efficiently. Different types of parapodia exist, with some being more developed for swimming, while others are adapted for crawling or burrowing, showcasing the diversity of life in aquatic environments.