1. Laboratory Investigation
The Science and Ethics of
Stem Cell Research
Plenty of Planaria
Laboratory Investigation

3. What are Planaria? Freshwater flatworms (phylum: Platyhelminthes)
Live in freshwater under leaves and stones
Avoid light (“negative phototaxis”)
Free living – not parasites
Carnivores – eat decaying meat, insects and larvae (egg yolks or liver in the lab)
1-20 mm in size
Long lived
Use sexual or asexual reproduction
This picture has been released it into the public domain.

4. Overview of Brown Planaria Dugesia tigrina

5. Planaria are complex organisms
Gastrovascular
System

6. Nervous
System

7. Reproductive
System

8. Excretory/Osmoregulatory
System

9. Why study Planaria to learn about stem cells?
Planaria have an amazing ability to regenerate parts of themselves
Planaria regeneration is a great model for demonstrating stem cell function and complexity of tissue regeneration
They can grow easily in the lab
1/279th

10. Neoblast = Planaria Stem Cell
20-30% of all the cells in a planaria are Neoblasts.
Neoblasts divide by mitosis and can make more of themselves. They are the only dividing cells in planaria.
When a planaria is wounded, neoblasts migrate to the site and begin dividing
Neoblasts can become ANY cell the planaria needs—nerve cells, flame cells, reproductive cells…
Ann. Rev. Cell. Dev. Biol. 20: , 2004

11. Three types of planaria with their neoblasts labeled with BrdU
BrdU (bromodeoxyuridine) is
substituted for thymine during DNA replication. Only dividing cells—in this
case the neoblasts—will show
detectible amounts of BrdU.
A. Phagocata sp.
B. Girardia dorotocephala
C. Schmidtea mediterranea
Dugesia sp.
(Dev. Biol 220: , 2000)

12. Neoblasts and Stem Cells are Totipotent
“Totipotent” Stem Cell
Blood Nerve Skin
They can become any cell type in the body
In Humans: Totipotent cells are limited to
early embryonic division
In Planaria: Neoblasts are always present

13. Regeneration requires…
turning on the
right genes at the
right time
in the cells that come from the dividing stem cells (neoblast).

14. Care and Feeding of Planaria
The water is very important! Fresh water from a pond, stream or lake is best; spring water is adequate
Keep cultures in a cool, dark place
Feed planaria at least once a week
Change the water twice a week, especially after feeding
After cutting them, the cultures should not be fed

15. Student Laboratory Investigation
Each team will receive 3 planaria:
Experimental Planaria #1
Every team will cut this into half, separating
the anterior from the posterior halves.
Experimental Planaria #2
This will be cut in a manner determined by your team.
Control Planaria
This will not be cut.
Used with permission from UC Museum of Paleontology

16. Plenty of Planaria

17. Planaria Regeneration, Days 1 - 14
Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley

18. Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley

19. Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley