University of Pittsburgh at Bradford
Science In Motion
Biology Lab 013
Planarian Regeneration
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 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.
These undifferentiated cells will eventually differentiate into the missing parts.
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 headend 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:
Pipettes
“I” Petri dishes
Razor blades
Dissecting scope or magnifying glass
Slides
Planaria culture
Stream water
Sharpie markers
Ice
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. Sketch your Planaria and
identify the following structures.
pigment cups – eyespots, photoreceptors
pharynx – used to suck food into the gut
mouth – food intake and output
auricle - ear-like extensions where chemical receptors are located
anterior and posterior intestine – digestion
cerebral ganglion – brain
lateral nerve cord – nervous system
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2. There are several classical types of cuts that can be made to your Planaria that should generate good
results. See the following page to determine which type of cut you would like to make.
a. Slow the Planaria’s movements by chilling the slide on ice.
b. Using a razor blade or scalpel, make the desired cut(s) to your Planaria.
c. Place the pieces obtained from the cut in individual Petri dishes with fresh pond water.
d. 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).
e. Describe your experiment below. Include a hypothesis for your experiment.
3. 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.
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4. Observations: Each time you change the water, observe your Planaria using a scope or magnifying
glass and note any changes you see. Record observations below. ** Record the date of your
observations. It will take two to three weeks for regeneration to be completed.
DATE
OBSERVATIONS
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