Article
Article
Polycladida
Article By:
Tyler, Seth Department of Zoology, University of Maine, Orono, Maine.
Last reviewed:January 2021
DOI:https://doi.org/10.1036/1097-8542.534100
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A taxon of turbellarian platyhelminth worms that are characterized by a multibranched gut and a muscular, protrusible pharynx. Members of the Polycladida (polyclads) are among the largest and most spectacularly colorful of the free-living flatworms. They are typically leaf-shaped, very flat, and often broadly oval; in a few cases, they are ribbon-shaped (Fig. 1). In general, their length is in the range of 10–70 mm (0.4–2.75 in.), although one has been measured as long as 150 mm (5.9 in.), and they are 1 mm (0.04 in.) to a few millimeters in thickness. Most polyclads live in marine habitats and glide over rocks, gravel, sand, mud, or reefs, appressed to the surface; some, though, are pelagic, swimming in the open ocean. In addition, a few species are found in the freshwaters of Indo-Malaysia. See also: Platyhelminthes; Turbellaria
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