bellmait.htm

The worms crawl in-- and do lots of other things

(Observations of anatomy and behavior of

Lumbriculus variegatus)

Marc Avery Bellow and Laura Lincoln Maitland

Overview

Students make observations of an easy-to-raise aquatic segmented worm, Lumbriculus variegatus, in this low technology laboratory investigation which is especially effective for introducing life processes.

Biological Concept

Organisms carry out life processes of nutrition, transport, regulation, locomotion and removal of wastes, aspects of which are readily observable in Lumbriculus variegatus.

Class Time

This laboratory investigation requires 1-2 class periods of 35-50 minutes.

Background Information

Lumbriculus variegatus, California blackworm, is better to use for observing life processes than its oligochaete relative, Lumbricus terrestris because it is almost transparent. Blood is pumped from the posterior, narrow end of the worm through the dorsal blood vessel to the anterior, thicker end. The blood is carried back to the posterior through the ventral blood vessel that does not pulsate. Circulation is evident because the blood is colored red by a pigment similar to hemoglobin which can also carry oxygen.

The Lumbriculus variegatus crawls when the circular muscles contract causing segments to elongate and longitudinal muscles contract causing segments to shorten. The waves of contractions move in direction opposite to the direction of movement of the worm. Setae, bristles, may be evident protruding from shortened segments as in the earthworm. The worm can also swim when muscles contract asymmetrically bending its body and resulting in an undulation of the body if the posterior is stimulated. If the anterior is similarly stimulated the worm curls and turns in the opposite direction which is termed "reversal behavior."

Recently fed worms can be observed ingesting food or egesting wastes.

Materials

• Lumbriculus variegatus (California blackworm) culture.

• filter paper circles

• disposable Petri dishes (small and medium sizes)

• watch or clock with second hand

• disposable transfer pipettes or droppers

• a short lenght of thin rubber band taped to the end of an aplicator stick creating a flexible tip

• a soft sable brush can be substituted for the above

• spring water or dechlorinated water (aged tap water)

• dissecting microscopes or magnifying lenses

[New plastic or glass slides or Petri dishes should be used because soap/detergent residues are lethal to the worms. Spring water is preferable for its mineral content, but tap water may be substituted if it first sits for two days to eliminate the chlorine.]

Extensions/Variations

This activity can be combined with parts of others described elsewhere in this module. (See amputation and regeneration.)

Resources

Charles D. Drews. "Those Wonderful Worms." Carolina Tips. August 1996, pp. 1-4.

Drewes, C.D. and C. R. Fourtner. "1990 Morphallaxis in an aquatic oligochaete, Lumbriculus variegatus: Reorganization of escape reflexes in regenerating body fragments." Developmental Biology, 138:94-103.

About The Authors

Marc Avery Bellow is a teacher of biology and AP psychology at Benjamin Cardozo H. S., 57-00 223 Street, Bayside, NY 11364. The school’s fax number is 718 631-7880. He can also be contacted by e-mail at jam13@ix.netcom.com

Laura Lincoln Maitland is a teacher of biology and AP psychology as well as the Science Department Chair at W.C. Mepham High School in Bellmore, NY. She can be contacted at Mepham H.S., 2401 Camp Avenue, Bellmore, NY 11710-3099. Her school phone number is: 516 623-8900, and the school fax number is: 516 785-7590.

NAME: ________________________________ DATE: ______________ PERIOD: _____

The worms crawl in-- and do lots of other things

(Observations of anatomy and behavior of Lumbriculus variegatus)

Introduction:

In this activity you will observe aspects of the anatomy and behavior of an aquatic worm, the California blackworm. Its scientific name is Lumbriculus variegatus. Be sure to use new glass or plastic Petri dishes in this activity. Even a trace of soap or detergent could kill the worms you’ll be observing. Your worm is a living organism, so please be careful in your treatment of it.

Materials:

Lumbriculus variegatus (California blackworm) culture filter paper circles

disposable Petri dishes (small and medium sizes) watch or clock with second hand

disposable transfer pipettes or droppers spring water or aged tap water

metric ruler widget or small sable brush

Procedure:

1. Make a widget as directed by your teacher for touching your worm, or use a paint brush to touch it.

2. Prepare an observation set-up as follows: Obtain two plastic Petri dishes that are different sizes. Place a piece of filter paper in the larger of the two Petri dishes. (It may be necessary to trim the filter paper disk to size.) Moisten the filter paper disk with some spring water (or aged--but not fresh tap water). Place the smaller Petri dish upside down in the middle of the first dish.

Pipette off any excess water.

3. Take your Petri dish set-up to the table with the worm culture. Obtain a worm for study from the culture container by using a transfer pipette. Place the opening of a plastic transfer pipette or medicine dropper near a worm. Use a rapid suction to draw up one worm into the lumen of the pipette. Expel the worm onto the filter paper near the inverted dish. Carefully use the pipette to remove any excess water. A torn edge of brown paper towel may also be used for this purpose. You should leave only a film of water between the inverted edge of the smaller Petri dish and the moist filter paper disk. You may gently use your "widget" or brush to coax your worm into position. An effective way to coax your worm is to first place your widget into the film of water and then gently nudge the organism near one end.

Observations:

1. Observe your specimen of Lumbriculus variegatus for several minutes without any aids, then observe the worm using a magnifier or dissection microscope. Describe your worm’s physical characteristics. Include color, shape and measurements.

2. Determine which is the worm’s anterior end and which is the posterior end.

a. Describe the relative thickness of the segments at each end.

b. Do any segments appear flattened at either end?

3. Use a gentle touch from your widget to prod your worm’s posterior end. Observe its behavior for two minutes. Now gently prod the worm’s anterior end. Again observe the worm’s response. Describe how the worm moves. How many segments are contracted. How many are constricted? Describe the location of the zone or zones of contraction.

4. Describe the direction of blood flow. (The pulsations look like tiny pink sausages moving along in a row. )

5. a. Select a reference point about 10 segments from the anterior end. Count the number of blood pulsations that move past that point in 20 seconds. A partner will time you as you count. Repeat this procedure about 10 segments from the posterior end. Again make three separate counts of 20 seconds duration. Calculate the average number for each position and record the number here.

Average number of pulsations per minute at the anterior end.

Average number of pulsations per minute at the posterior end.

b. Compare your average results with the averaged class totals. Make any other calculations that your teacher asks for in this space.

6. Go over to the culture container from which you obtained your worm. Observe the behavior of the worms in the container. Fill your transfer pipette with water and use a jet of water to wash your worm into the culture. Describe any aspects of the worm’s life activities that you observe which you haven’t already mentioned.