Does Heat Influence Planaria Flatworm Location?

Planaria flatworms swim away from both light and heat. They show the strongest photophobic responses to ultraviolet (UV) light and clear thermotaxic responses to temperatures above 30°C. This experiment seeks to test whether planaria can be conditioned to swim towards light when exposed to heat as a negative stimulus. Previous research suggests that planaria can learn through conditioning when exposed to different types of sweeteners in both dark and light environments. We predict that if planaria think that dark environments will be warmer, then they would choose to swim towards the light when given the choice between the two environments. During the conditioning period, planaria will be placed entirely under a UV light in room temperature water for a period of time, and then be placed in the dark in warm water. If the conditioning is successful, the majority of planaria would go against their typical behavior and would swim toward the light when exposed to both environments. They would successfully be conditioned to demonstrate a positive phototaxic response due to heat as a negative stimulus. Future research questions will focus on environmental toxicant effects on positive phototaxic responses in planaria.