Investigation: Planarians and Regeneration
You will receive a small petri dish with a flatworm inside it. The flatworm is the freshwater planarian, also known as Dugesia. For more information on the planarian, check out this Article on the Planarian or read the related chapter in your textbook.
Planarians can be purchased from Amazon or biological supply companies.
Prelab Questions
1. To what kingdom do planarians belong?
What phylum?
2. What type of symmetry does this worm have?
3. Where do planarians live?
Observations and Experiments on the Flatworm
4. Observe your worm, using a microscope or hand lens. Sketch the planarian below. Label the eyespots. Label the anterior and posterior ends. Pay attention to detail on your sketch!
5. Measure your planarian. This operation is best performd by removing some of the water from the dish and waiting for the worm to stretch out. Measure the length of the worm in millimeters. (Always replace the water, you can use the dish lid to transfer water to and from the planarian environment.)
.................................
Length of Planarian _______
Write your length on the board and when all the lengths are down, determine the average planarian size.
Average ___________
6. Planarians actually display a handedness, being right or left handed. You can discover whether your worm is right or left handed by flipping the planarian over on its dorsal (back) and seeing which way it recovers. If it rolls to the right, it is right handed, if it rolls to the left, it is left handed. Do five trials to determine the handedness of your planarian.
| Trial 1 | Trial 2 | Trial 3 | Trial 4 | Trial 5 | |
| Which way did it roll? | |||||
| Based on your data, is your planarian right or left handed? ____________ | |||||
8. Design an experiment to test the planarians reaction to light and dark. You will have flashlights and the room will be darkened for this part of the lab. Describe your experiment and be detailed enough that someone else could perform the exact same experiment. You can even use a numbered list to describe your procedure.
Conduct your experiment to determine whether the planarian prefers light or dark. Construct a data table.
Planarian Reproduction
10. Planarians are hermaphrodites. Define hermaphrodite
Planarians can also reproduce by regeneration.Define regeneration
Is this method of reproduction sexual or asexual?
12. Pour out some of the water, so that the planarian is mostly un-submerged. When it stretches out, use a razor blade to cut it cleanly in half. Replace the water and put the lid on it. Observe the two pieces of the planarian under the microscope or with a hand lens.
Describe how each of the cut halves is behaving. Are they both moving? Is one moving more than the other? Is there obvious damage to the tissue of the animal?
Make Predictions:
How long do you think (in days) will it take for your planarian to completely regenerate?
Will both sides (or parts) regenerate?
Label the lid with your NAME and HOUR.
Other Resources
Planaria Article – description of a planaria, with questions