Planarian Dugesia sp. showed response to both gravity and light
Planarian Dugesia sp. showed response to both gravity and light. While planarian Dugesia sp. demonstrated negative phototaxis, they demonstrated positive geotaxis. The null hypotheses, the planarian Dugesia sp. shows no response to gravity and planarian Dugesia sp. shows no response to light, were therefore rejected. Instead, the hypotheses that planarian Dugesia sp. shows response to gravity and Dugesia sp. shows response to light, were supported.
When planarians are exposed to light, their activity tends to increase and this makes the resting planarians to start moving. In addition, already moving planarians usually increase their motion once presented with light. In essence, the planarians finally rest in the region of the container which is less illuminated (Khanna, 2004). Khanna (2004) explains that planarians are phobotactic and they avoid light by random movements, tending to react negatively when they are in more lighted areas and they fail to react once they come into a less lighted area. Even when planarians have their eyes removed, they still tend to avoid lighted areas in their environment and instead settle in darker parts. This response is exhibited even in decapitated planarians, only that the rate of movement slows down (Khanna, 2004).
