what are planarians
Planaria. Planaria (Platyhelminthes) are free-living flatworms that live in freshwater. They are typically found under rocks and debris in streams, ponds, and springs. Planarians are interesting to study for a variety of reasons. First, planarians have bilateral symmetry with two nerves extending the length of the body, an enlarged brain (ganglion cell), and two eye spots. The eye spots are sensitive to light. Planarians move away from the light and are most active in the dark. Second, light and water current can be used demonstrate kinesis (change of speed) and taxis (change of direction).
Planaria feed by sucking food into their gastro vascular cavity through a tube called the pharynx. The pharynx is located on the mid-ventral surface. Planaria are common to many parts of the world, living in both saltwater and freshwater ponds and rivers. Some species are terrestrial and are found on plants in humid a … reas. 10 people found this useful.