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Project Summary

Difficulty	7
Time required	Long (a couple of weeks)
Prerequisites	None
Material Availability	Specialty items
Cost	Average ($50 - $100)
Safety	Use strong magnets with care! See safety notes below.

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Objective

The goal of this project is to test the hypothesis that magnetic fields can increase the regeneration rate of planaria.

Introduction

Planaria are flatworms (platyhelminthes) that live in freshwater. They are simple organisms with three tissue layers (ectoderm, mesoderm, and endoderm) but no body cavity. They are remarkable for their ability to regenerate.

Figure 1. A Planaria flatworm. Note the light-sensitive eyespots on the head. Image courtesy BioMedia Associates.

Anatomical terms are used to describe the procedure for bisecting the planaria, so you will need to understand the following terms in italics. The head end of the planaria (with eyespots) is the anterior, and the tail end is the posterior. The dorsal surface is the one that is normally facing up (the "back" of the planaria). The ventral surface is the one that is normally facing down (the "front" of the planaria). The ventral surface contains the pharynx, through which planaria feed.

In this project you will be investigating whether strong magnetic fields have any effect on regeneration in planaria. See the Variations section for additional ideas for experiments on regeneration.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• regeneration,
• anatomical terms:
  • anterior,
  • posterior,
  • dorsal,
  • ventral,
  • pharynx,
  • bisect.

Bibliography

• Wikipedia contributors, 2006. "Planarium," Wikipedia, The Free Encyclopedia [accessed August 2, 2006] http://en.wikipedia.org/w/index.php?title=Planarium&oldid=64512073.
• BioMedia Associates, 2006. "Biology Classics: Planaria," BioMedia Associates [accessed August 2, 2006] http://ebiomedia.com/gall/classics/Plan/plan_about.html.
• K&J Magnetics, 2006. "Neodymium Magnet Safety," [accessed August 2, 2006] http://www.kjmagnetics.com/safety.asp.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• at least 30 live planaria,
  Notes on sources:
  • If you want to try collecting planaria yourself, here are some tips from BioMedia Associates: "It's usually not difficult to find planarians. Shake pond weeds into a pan—flatworms will often be dislodged from their hiding places. Turn over stream rocks and look carefully at the rock surfaces." (BioMedia Associates, 2006) Once you've found them, here is a method for collecting them:
    • "Put a small pellet of canned pet food in an old nylon stocking.
    • "Secure this bag of attractant in the stream or pond bed overnight.
    • "With any luck, in the morning you will find a collection of flatworms crawling over the bag." (BioMedia Associates, 2006)
  • Planaria are also available online from these sources (because availability can vary with the season, be sure to check with them by phone first to make sure that the critters are in stock when you plan to do your project):
    • Carolina Biological http://www.carolina.com;
    • Ward's Natural Science http://wardsci.com/default.asp.
• ice,
• scalpel or razor blade,
• spring water or pond water,
• 6 shallow containers for planaria (e.g., 100 mm diameter Petri dishes),
• 6 pieces of steel sheet metal, each approx. 100 mm square,
• neodymium magnets of same outer dimensions, but increasing strength (3 values),
  Notes on sources:
  • available online from K&J Magnetics, http://www.kjmagnetics.com;
  • choose magnets with the same outside dimension, but with increasing surface field strength (e.g., part numbers D901, D91, D92);
  • buy at least 21 magnets of the two lower strengths, and 42 of the highest strength (used for two groups of planaria).

Disclaimer: Science Buddies occasionally provides information (such as part numbers, supplier names, and supplier weblinks) to assist our users in locating specialty items for individual projects. The information is provided solely as a convenience to our users. We do our best to make sure that part numbers and descriptions are accurate when first listed. However, since part numbers do change as items are obsoleted or improved, please send us an email if you run across any parts that are no longer available. We also do our best to make sure that any listed supplier provides prompt, courteous service. Science Buddies receives no consideration, financial or otherwise, from suppliers for these listings. (The sole exception is any Amazon.com or Barnes&Noble.com link.) If you have any comments (positive or negative) related to purchases you've made for science fair projects from recommendations on our site, please let us know. Write to us at scibuddy@sciencebuddies.org.

Experimental Procedure

1. You will be dividing your planaria into 6 groups, according to the table, below. Groups 1–4 will be bisected (cut in half), and exposed to various magnetic field intensities (weakest = strength 1, strongest = strength 3). Groups 5 and 6 will be unoperated (whole animal) controls. Group 5 is not exposed to an increased magnetic field; group 6 is exposed to the strongest magnetic field (strength 3).

   Group #	Condition	Magnet
   1	bisected	no magnets (plain sheet metal underneath)
   2	bisected	+ magnets, strength 1
   3	bisected	+ magnets, strength 2
   4	bisected	+ magnets, strength 3
   5	untreated	no magnets (plain sheet metal underneath)
   6	untreated	+ magnets, strength 3

2. Label the sheet metal squares 1–6.
3. Space the appropriate magnets evenly over a 100 mm circle (i.e., the size of the petri dish) on sheet metal squares 2, 3, 4, and 6 (see table, above). All of the magnets should be arranged with the same pole (either N or S) facing up. The sheet metal allows you to place the magnets closer together than you would on a non-magnetic surface, and also increases the magnetic field strength.
4. Label the dishes 1–6 and place them on top of the correct sheet metal square.
5. To bisect a planarian, use the following procedure:
   1. Place it on ice to immobilize and anesthetize the animal.
   2. Cut it in half with a scalpel or single-edged razor blade. Make the cut midway between the anterior (head) and posterior (tail) ends of the animal. Take care not to cut yourself!
   3. Immediately place the bisected pieces in the appropriate petri dish containing fresh spring or pond water.
6. For this experiment, you will need to bisect 20 planaria (5 each for groups 1–4, assumes a total of 30 planaria available).
7. Keep the petri dishes covered, and keep all of the dishes at the same temperature, in a place that is not exposed to bright light.
8. Do not feed the planaria during the regeneration period. They are unlikely to feed during this time, so uneaten food will foul the water and the planaria will die.
9. It's a good idea to do a 10% water change every few days. (If the water looks cloudy, change more often and/or change a larger fraction of the water.) Follow the same procedure for all six dishes. Do not use tap water (tap water is generally treated with clorine or chloramine, which would be toxic to the planaria). Use spring water or fresh pond water for the water changes.
10. Observe the planaria daily. For each dish, measure the length of each of the segments and record the results. Also, record the lengths of the whole animals. Note any other observations you make.
11. At the end of two weeks, summarize your results. What is the average amount of regeneration for each experimental group? Is there a systematic difference in regeneration rate with magnetic field strength?
12. Calculate the average amount of regeneration for the head and tail sections separately. Is there any evidence for a difference in regeneration rates of the two segments?

Variations

• What happens if you bisect the planaria in half the other way (along the anterior-posterior axis, instead of across it)? Is the regeneration rate faster, slower, or the same?
• What happens if you cut the planaria into quarters? Which of the segments regenerates fastest?
• For a similar project with earthworms, see the Science Buddies project How Much Worm Is a Worm?.
• How do planaria orient to light? Cover half of the petri dish containing planaria with dark paper and expose the dish to light. Which side of the dish do the planaria prefer? Do you get the same result each time you repeat the experiment? What happens if you try this with bisected planaria? Do both segments react in the same way? Try this with a group of planaria bisected along the anterior-posterior axis and with a group bisected across the anterior-posterior axis.

• For more science project ideas in this area of science, see Zoology Project Ideas.

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

This project idea is from:

• Formaker-Olivas, B., 2004. "How Does the Intensity of a Magnetic Field Affect the Regeneration Rate of a Planarian?" California State Science Fair Abstract [accessed August 2, 2006] http://www.usc.edu/CSSF/History/2004/Projects/J1907.pdf.

Last edit date: 2006-08-30 00:00:00

Career Focus

If you like this project, you might want to think about career opportunities in Zoology.

Ever wondered what wild animals do all day, where a certain species lives, or how to make sure a species doesn't go extinct? Zoologists and wildlife biologists tackle all these questions. They study the behaviors and habitats of wild animals, while also working to maintain healthy populations, both in the wild and in captivity. Learn more about this career: Zoologist and Wildlife Biologist.