A Tail to Tell
The freshwater, segmented worm Lumbriculus has several unique adaptations that enable it to live successfully along the shore of ponds and marshes. In this activity the students observe populations of Lumbriculus to discover several of these adaptations and design and perform experiments to test their proposed hypotheses for these observed behaviors.
Experimental Design Proximate and Ultimate Causation
The activity, including discussion time, will require approximately 2 class periods. The periods need not be on consecutive days. The Further Investigation is highly recommended and will require time to set-up (1/2 -1 period) followed by 5 minutes of daily observation for 5-7 days.
Background Information ough the dorsal blood vessel. In the vertical posture the worm is more vulnerable to surface or aerial predators. Tail photoreceptors enable Lumbriculus to quickly withdraw its exposed tail in what is called the"shadow reflex".
Culture containers (glass or plastic work well; need only be 4-6 inches deep)
Spring water (bottled from the store may be used)
Divide the population of Lumbriculus between two culture containers A and B. The water depth should be approximately 2-3 times the length of the worms. Aerate the water in container A but not B. An optional third container, C, could be set up with less water so as to observe the tail-binding behavior. Do not place the containers in direct sunlight.
Begin the activity by having groups of students perform Part I of the activity. To maintain the true spirit of exploration, there should be minimal input from the teacher. If only one set of containers has been set-up for the entire class to observe, have the teams discuss their responses to the Day I questions 1-3 and decide on the best experiment to perform. While waiting their turn to do this activity, other teams could begin observing blood flow in Lumbriculus.. Worms are placed on a moist filter paper in a Petri dish and observed with a hand lens or stereoscopic microscope. Blood flows from the posterior to the anterior end; pulse can easily be determined. See Lumbriculus module for additional experimental information and ideas.
A simple experiment for question 3 would be to switch the aerator to tank B.
Do not give the students the Further Investigation until they have completed question 8.
In so doing,you will not be giving the students clues that might perhaps stifle their
creativity in Part I.
Information on cutting the worms for the Further Investigation can be found in the Introduction to Lumbriculus. Even with tail segments, the vertical tail orientation and "shadow reflex" persist. It would be interesting to determine the minimal number of segments needed for the continuation of this response.
Drewes, Charles D. 1990. Tell-tail Adaptations for Respiration and Rapid Escape in a
Freshwater Oligochaete (Lumbriculus variegatus Müll). Journal Iowa Academy
Science. 97(4): 112-114.
About the Author
Judy Lachvayder,a biology and chemistry teacher at Parma Senior High School, can be contacted at Parma Senior High School, 6285 West 54th Street, Parma, OH 44129 or Fax 216/885-8684 or e-mail jlachvAE@ix.netcom.com.
NAME: _____________ DATE: ___________ PERIOD:_________
A TAIL TO TELL
Before going fishing, people often stop to dig or buy earthworms to use as bait. Not all members of the oligochetes, however, are terrestrial. Some, such as Lumbriculus variegatus, live in the water. Their favorite habitat is the murky shoreline of ponds and marshes. Perhaps this is why they are also called mud worms or California black worms. These creatures are wonderfully adapted to their environment. Lets see how many of these adaptations you can discover.
PART 1 (Day 1)
Carefully observe the population of worms dwelling in container A and container B. Be careful not to bump or lean over the containers while making observations.
1. Describe the differences that you see between:
(A) the way in which the two containers are set-up
(B) the way the organisms are behaving in each container. Include a drawing.
2. Based on your observations for the way the ends of the worm are positioned in each container,
write a plausible explanation (hypothesis)
3. Design an experiment to test this explanation.
Observe the worms again. This time pass an object (sheet of paper or cardboard) over the top of the container to create a shadow.
4. Describe how the Lumbriculus responded.
5. What must be present for this response to occur?
6. How is this behavior useful to the Lumbriculus?
7. Set up the experiment to test your hypothesis in question 3. Write a summary of what you did.
PART 2 (Day 2)
8. Observe the Lmbriculus lab that you set up yesterday.
A. Record you observations.
B. Evaluate your hypothesis. Explain why your data supported or did not support
C. What can you conclude about the reason for this behavior?
How much of the animal is involved in the aeration and/or shadow response?
Design and perform an experiment to answer to this question. As you design your experiment,
recall that: (1) Lumbriculus have amazing powers of regeneration, and (2) blood flows anteriorly in the dorsal blood vessel.