what sensory structures do planarians have
Sensory Structures of a Flatworm. Flatworms live in many environments. Jupiterimages/Photos.com/Getty Images. Flatworms, also called planarians, belong to the phylum Platyhelminthes. Characterized by flat bodies, they have no circulatory or respiratory organs and a very simple digestive tract.This body plan limits them to very small, flat shapes to allow them to absorb oxygen and moisture.owever, a flatwormâs body contains the beginnings of more complex structures found in other animals. For example, eye spots resemble the ancestral forms found in more complex animals. Understanding flatworm sensory structures can help you understand the origins of these organs.