How do planarians and tapeworms differ in their ability to detect light?

Planarians and tapeworms exhibit different mechanisms and abilities in detecting light, showcasing variations in their sensory capabilities.

Planarians:

Planarians are flatworms known for their remarkable regenerative abilities. They possess photoreceptors called eyespots, which allow them to detect the presence or absence of light. Each eyespot consists of a group of light-sensitive cells, allowing planarians to discern changes in light intensity. These eyespots function similarly to simple light meters, enabling them to move toward or away from a light source. Their eyespots help them navigate their environment, avoid direct sunlight, and find optimal habitats with suitable lighting conditions.

Tapeworms:

Tapeworms, in contrast, are parasitic flatworms that lack specialized photoreceptors. They do not possess eyespots or any apparent light-sensing structures. This means they cannot directly detect light or respond to changes in light intensity. Tapeworms primarily rely on chemical cues and their host's environment for orientation and survival.

In summary, planarians have functional light-sensing structures called eyespots that allow them to detect changes in light intensity and respond to environmental lighting conditions. Tapeworms, on the other hand, lack any known light-sensing structures, so they cannot directly detect or respond to light.