Tyler, Seth Department of Zoology, University of Maine, Orono, Maine.
Last reviewed:August 2015
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- Body form and color
- Body wall
- Gut and feeding
- Circulation and excretion
- Nervous system and sensory organs
- Sexual reproduction
- Additional Reading
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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