Are Worms Sensitive to Light?

Last week at McDevitt Middle School, students in Mrs. Murray’s science Cluster Challenge designed simple experiments to find out if worms are sensitive to light. Students worked alone and in groups to develop a hypothesis (a predicted result), an experimental procedure (a means of testing a hypothesis), and a conclusion (what was observed during the experiment and possible causes of the result).

Students used classroom materials such as empty boxes, black and brown construction paper, and flashlights to see what happens when worms are placed in light or dark conditions but given the option to move between the two constructed environments. Each experiment used a sample size (the number of things being observed or tested in a scientific study) of 6-10 different worms in order to ensure results that better represent typical behavior of the general red wiggler population (the total number of organisms for a defined area or group; can be very specific, like 4th grade students at Northeast Elementary, or very broad, like all Waltham students under the age of 18).

After trying several techniques to see if the worms liked or disliked being exposed to light, students concluded that worms are definitely sensitive to light. They almost always tried to slither into darkness when under the flashlight! Even when they were simply sitting on a table, the worms tried whatever they could to escape light, as you can see in the picture below.

Why might worms be so sensitive to light? Since we know that worms need their skin to stay nice and moist so they can breathe, it makes sense that worms feel threatened by light exposure that could potentially heat them up and dry them out. Their reaction (to slither into darkness) is a survival mechanism, or a behavior intended to protect themselves against predators or threatening aspects of their natural environment, such as sunlight.

Rebekah

Why do you think they are wrapping around each other in the petri (pronounced "pee-tree") dish?

Despite annoying them for a little while, no worms were harmed in our experiment. Images by Rebekah Carter (2011).

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