Planarian Regeneration Lab

Name______Advanced Biology

Introduction:

Planaria are one of many free-living flat worms that can be found in marine, aquatic, and terrestrial environments. Typical characteristics include an acoelomate (no body cavity) body, a gut with no anus, lack of a blood vascular system, and a simple nervous system. Planaria are carnivorous scavengers. Planaria have been the subject of many studies because of their unusual ability to regenerate. Regeneration is the ability to “re-grow” lost body parts. This is possible because the organism has the ability to form a blastema, which is an accumulation of undifferentiated cells, at the site of the wound. (We saw this in the salamander video!) These undifferentiated cells will eventually differentiate into the missing parts.

Interesting Fact: Planarian flatworms reproduce by taking advantage of their regeneration capabilities. When conditions are favorable, the organism will attach its tail- end to the ground and pull forward with its head-end until it tears itself in half. Each end will then regenerate its missing half. This is a form of asexual reproduction called fission. The two “new” planaria are clones of each other, both possessing identical genes.

In this laboratory activity, you will study patterns of regeneration in planaria by conducting your own regeneration experiment. It will be your responsibility to care for your organisms and to keep records of their developmental progress by recording your observations.

Materials: Planarian, Microscope, Scalpel, Water (preferably pond water) 1 Petri dishes

Procedure:

*When working with Planaria, you can slow its movement by placing the slide on ice for several minutes. 1. Before making any cuts to your planaria, examine it on a slide to try to identify the following anatomical structures. (An understanding of the Planaria anatomy is essential for determining if there was any regeneration or not!!) a. Catch a Planaria and put it on a microscope slide with a drop of water or place in a Petri dish to observe under the dissecting scope. b. View the Planaria using a dissecting scope or magnifying glass. Make a detailed drawing of Planaria.

Picture of Planaria before regeneration:

2. There are several classical types of cuts that can be made to your Planaria that should generate good results. See the following diagrams to determine which type of cut you would like to make.

Bisect Down the Two heads Two bottoms trisect middle

2 3. Slow the Planarian’s movements by chilling the slide on ice.

4. Using a razor blade or scalpel, make the desired cut(s) to your Planaria.

5. Place the pieces obtained from the cut in individual Petri dishes with fresh pond water.

6. Label the Petri dish with your name, the type of cut performed, and which piece is in the dish (i.e. head end, tail end, left side, right side, etc).

7. Planarian Care: Keep your experimental Planaria in a cool darkened area. Provide your Planaria with fresh stream water every other day. Remove the old water with a pipette, being careful not to accidentally dispose of your Planaria. Only use fresh pond, spring, or stream water – never tap water or distilled water. Also, do not feed.

8. Observations: Each time you change the water, observe your Planaria using a scope or magnifying glass and note any changes you see (think about what you need to include: what type of fragments you’re looking at, size, and presence of eyespots). Record observations below. ** Record the date of your observations. It will take two to three weeks for regeneration to be completed.

DATE OBSERVATIONS Day 0

3 Lab Questions: - To be during Day 0 of lab.

1. Hypothesize about your planarian. Which dissection cuts do you think will result in new planarian?

2. What environmental variables do you think may influence regeneration?

3. After you cut the planaria, how does the mobility of the tail fragments compare to the mobility of the head fragments? Do they move the same or differently? If they move differently, why do you think that is? (If you didn’t cut your planaria in a way that gives you a tail and a head, note the mobility of pieces that you did cut).

4. Do you think the head fragments prefer light or shade? How can you test this?

- To be completed on Final Day of regeneration (Probably day 8-10).

1. As the days went by, what did you notice about the color of the regenerating tissue?

2. Did all the tail fragments regenerate photoreceptors (eyespots)? If not, which fragments did not?

3. Did all the tail fragments regenerate photoreceptors at the same rate? If not, which were slower and which were faster?

4. What does the relative rate of appearance of photoreceptors in the different tail fragments tell you about the regeneration ability of different sections of the worm?

5. Did you notice a change in mobility in the tail fragments over time? What about the head fragments?

6. How could you test whether the regenerated photoreceptors are functional? Do you think photoreceptors are functional before, as soon as, or sometime after they become visible? Why?

4 7. How could testing photoreceptor function be useful in measuring the rate of head regeneration in tail fragments? Critical Thinking Question: 1. After learning about the importance of regeneration to certain species (planaria, newt, sea star, etc), where else might regeneration be important? To what species? Is regeneration related to the study of stem cells? How could the study of regenerative species be of importance to humans?