Now for a Lab on Planaria

When we learn about animals we learn about different Phyla (Different groups in the animal kingdom)

-We usually start by learning about the simplest animal and working our way up the phylogenetic tree of complexity in anatomy

-The simplest phyla is Porifera (Sea Sponges)

-Sponges have no organs and no true tissue

-They have no symmetry and no body layers

-They are more like a colony of single celled organisms working together to make up an animal

-For these reasons we say that Porifera have the simplest body plan

-The next simplest animal is Cnidaria (Sea Jellies and Corals)

-The Sea Jellies are diploblastic (Have two body layers)

-Ectoderm

-Mesoglea (Full of Jelly)

-Endoderm

-They have radial symmetry

-No brain but instead a nerve net

-The next in the level of complexity is the Platyhelminthes (Flat Worms)

-These guys are triploblastic (Three body layers)

-Ectoderm

-Mesoderm

-Endoderm

-They are acoelomates (no coelom)

-Have a very simple brain (Cannot feel pain)

-Eye spots that can see light

Planarians are a favorite organism for lab experiments because they have a large amount of stem cells. If you remember from last semester a stem cell can differentiate into a number of different cells. Stem cells can be used for regeneration. Because Planarians are full of stem cells they have amazing capabilities of regeneration. In our lab we will test the behavior of planarians and we will test their regenerative properties.

Observation of a Live Planarian

You will receive a small petri dish with a flatworm inside it. The flatworm is the freshwater planarian, also known as Dugesia. For more information on the planarian, check out this Article on the Planarian or read the related chapter in your textbook.

Prelab Questions

1. To what kingdom do planarians belong? ________________________ What phylum? __________________

2. What type of symmetry does this worm have?

3. Where do planarians live?

Observations and Experiments on the Flatworm

4. Observe your worm, using a microscope or hand lens. Sketch the planarian below. Label the eyespots. Label the anterior and posterior ends. Pay attention to detail on your sketch!

5. Measure your planarian. This operation is best performd by removing some of the water from the dish and waiting for the worm to stretch out. Measure the length of the worm in millimeters. (Always replace the water, you can use the dish lid to transfer water to and from the planarian environment.)

.................................................................... Length of Planarian _______

Write your length on the board and when all the lengths are down, determine the average planarian size. Average ___________

6. Observe the planarian for five minutes. Does the planarian seem active or passive? How does it move? Does it swim or creep? Where in the dish does it spend most of its time? Make a current in the water with a pipette. How does the planarian react? Fill out the table below.

7. Planarians actually display a handedness, being right or left handed. You can discover whether your worm is right or left handed by flipping the planarian over on its dorsal (back) and seeing which way it recovers. If it rolls to the right, it is right handed, if it rolls to the left, it is left handed. Do five trials to determine the handedness of your planarian.

8. Design an experiment to test the planarians reaction to light and dark. You will have flashlights and the room will be darkened for this part of the lab. Describe your experiment and be detailed enough that someone else could perform the exact same experiment. You can even use a numbered list to describe your procedure.

Conduct your experiment to determine whether the planarian prefers light or dark. Construct a data table.

Write your conclusions. Make sure you answer the question: Does the planarian prefer a light or dark environment and include your reasoning.

9. Drop a piece of food into the petri dish with the planarian. Observe the planarian's reactions. It may take a few minutes. How does it eat the food? Where is its mouth? Use the space below to write your observations.

What is the name of the tube used for feeding in the planarian?