The Sensory Basis of Planarian Behavior

Over the past few decades, planarians have emerged as a powerful model for regeneration research. Planarians can repair and regenerate their entire nervous system—including their brain and nerve cords—a rare ability among common model organisms. The planarian nervous system supports several sensory modalities, including vision, extraocular photosensation, chemosensation, thermosensation, mechanosensation, and nociception. This diverse array of sensory modalities gives rise to a wide range of behaviors and makes planarian worms a remarkable model for the study of sensory neuroscience. Furthermore, studying the processes that mediate the efficient repair and reorganization of their complex nervous system upon injury may yield new insight into the maintenance and regeneration of sensory systems in other organisms, including humans. In this review, we discuss the existing literature on the molecular drivers of planarian sensation, as well as the behaviors resulting from their sensory systems and multisensory integration.