Plenty of Planaria

Laboratory Investigation

The Science and Ethics of Stem Cell Research

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.

Overview of Brown Planaria

Dugesia tigrina

Planaria are complex organisms

GastrovascularSystem

Nervous System

Reproductive System

Excretory/OsmoregulatorySystem

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

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. 20:725-757, 2004

Three types of planariawith 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.

(Dev. Biol 220: 142-153, 2000)

A. Phagocata sp.B. Girardia dorotocephalaC. Schmidtea mediterranea

Dugesia sp.

Neoblasts and Stem Cells are Totipotent

In Humans: Totipotent cells are limited to early embryonic division

In Planaria: Neoblasts are always present

turning on the right genes at the right time in the cells that come from the

dividing stem cells (neoblast).

Regeneration requires…

Student Laboratory Investigation

Each team will receive 3 planaria:

Experimental Planaria #1Every team will cut this into half, separating

the anterior from the posterior halves.

Experimental Planaria #2This will be cut in a manner determined by your team.

Control PlanariaThis will not be cut.

Teacher keeps control.Used with permission from UC Museum of Paleontology

Plenty of Planaria

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

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

Student Laboratory Investigation

Question: What will happen when Planaria, an animal with neoblast cells, is cut in various regions of the body?

Hypothesis

IF: Planaria is cut in half (transverse: horizontal),

THEN: it will not die but regenerate new body parts,

BECAUSE: Planaria is an animal with neoblast cells, cells that divide by mitosis and can make more of themselves (like stem cells).

Student Laboratory Investigation

Materials:

At the table for each pair: 1 dissecting microscope 1 container of pond water (share) 1 container of Planaria (share) 3 Petri Dishes 2 microscope slides 1 razor blade 1 pipet 1 ruler 1 Sharpie 1 Paint brush Used with permission from UC Museum of Paleontology

:

Student Laboratory Investigation

Data:Copy chart into your lab book. Repeat for Planaria 2 and 3

Planaria 1 Tues 11/2 Thurs 11/5 Tues 11/9 Fri 11/12

Drawing

Length before(cm) x x xLength after (cm)

Behavior before x x xBehavior after

Other observations

Student Laboratory InvestigationProcedure:

1. Label your petri dishes: Planaria #1,#2, Team name, period. Fill each ½ full with pond water.

2. Using the pipet, put one drop of pond water on slide.

3. Using paint brush, collect one Planaria and place on slide. Sketch, measure, and observe.

4. TO CUT: use 2nd slide as a platform. Use pipet or brush to transfer Planaria.

5. Put slide under scope and cut with blade. Sketch, measure, and observe.

6. Place Planaria parts into correct petri dish.

7. Repeat for Planaria #2 using a different cut.

8. For Control (#3): follow procedures but do not cut!