When the Sun Rises: The Effect of Light on the Movement of Daphnia

Abstract

Changes in the environment, or stimuli, affect your behavior and movement over the course of a day: When you get cold, for instance, you might get up and put on a sweater. Or if it is sunny and warm, you might go outside to play sports or go for a walk. Different stimuli, including light, affect the movement of other organisms as well. But how does the type of light influence their movement? Do they respond differently to different kinds of light, depending on other factors in their surroundings? In this science project, you will investigate how different lights affect the movement and swimming patterns of water fleas (Daphnia magna) in three different aquatic environments.

Daphnia magna, commonly known as water fleas, are tiny freshwater crustaceans. They are filter feeders and can survive in culture (like an aquarium) by eating algae, bacteria, or yeast. A picture of a Daphnia is shown in Figure 1 below. You can purchase a culture kit from Carolina Biological Supply Company or you may be able to purchase them at a tropical fish store. (For more suggestions on specialty items you may need to culture Daphnia, check out the Materials section of a different Science Buddies science project that also uses Daphnia, Using Daphnia to Monitor Water Toxicity. Although they are small, Daphnia are big enough that you can easily watch them moving around in a fishbowl or small jar.

For this science project, you should first investigate how Daphnia normally migrate and swim around in different aquatic environments. Three different aquatic environments you can create and test include test tubes of water, large containers of water that simulate their pond habitat, and a real pond. How do the Daphnia swim during the day, when there is light, compared to when it is dark? In what direction do they swim? Do they show different patterns in where and how they move?

After you have investigated Daphnia's migration pattern in response to normal light, try testing different lighting sources to see how they change the movement patterns of the Daphnia. How do different artificial lights affect Daphnia's movement? Do different colored lights affect the movement, and, if so, do they affect it in a different way than the regular artificial lights? Can you explain their behavior? Even the tiny Daphnia can display complex behaviors in response to their environment!

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Last edit date: 2020-06-23

Experimental Procedure

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Variations

• How do other stimuli affect the movement of Daphnia? Think of other environmental factors, such as food availability, the presence of predators, or temperature, and devise a way to test how these other factors might affect Daphnia's movement.
• For other science project ideas that use Daphnia, see:
  • Using Daphnia to Monitor Water Toxicity
  • Caffeine and Heart Rate: A Pharmacological Study Using Daphnia magna

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