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 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:

Pipettes Dissecting scope or magnifying glass Stream water

“I” Petri dishes Slides Sharpie markers

Razor blades Planaria culture 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!!)
  2. 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.
  3. 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

  1. 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.
  2. Slow the Planaria’s movements by chilling the slide on ice.
  3. Using a razor blade or scalpel, make the desired cut(s) to your Planaria.
  4. Place the pieces obtained from the cut in individual Petri dishes with fresh pond water.
  5. 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).
  6. Describe your experiment below. Include a hypothesis for your experiment.
  1. 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.
  1. 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

1