The Effects of Ultraviolet Light on Lumbriculus

Kay Widmer

Overview

With the growth of the hole in the ozone layer in the upper atmosphere, increasing amounts of ultraviolet light are reaching the earth. Very little of this light actually penetrates the water where Lumbriculus is found, but the worm has been observed sticking its tail up out of the affect the worm or parts of the worm. To date, no published research has been done on this aspect of this worms' reaction to its environment.

Biological Concepts

• Animal Behavior • Ecology

• Evolution • Proximate and Ultimate Causation

Class Time

This activity will require 15 minutes per day for 2-3 weeks.

Background Information

For information on the acquistion and care of Lumbriculus, refer to the "Introduction to Lumbriculus."

Ultraviolet light comes in both short and long wavelengths. The long wave ultraviolet light does not appear to do any damage to the worms. When exposed to long wave UV light for 10 minutes at a distance of 7 cm, there did not seem to be any damage. In contrast, the short wave radiation did massive damage after very short exposure. In general the longer the exposure, the quicker the worms died. At 24 cm, the worms died in a few hours when exposed to 2 minutes of short wave radiation. When exposed to one minute 45 seconds of radiation they did not die until after 48 hours. At 50 seconds exposure they died in 3 days.

Materials

• Lumbriculus worm culture

• 1- 5 cm petri dish

• filter paper to fit petri dish

• spring water

• 1 pipette

• 1 short wave ultraviolet light

• 1 long wave ultraviolet light (optional) 4 watt, 115 volts, .12 amps, 60 cycles

• 1 stand for the UV light -a ring stand with a large ring clamp will surfice

• 1 meter stick

• 1 watch or clock with a second hand

• 1 stereo microscope

• 1 deep well culture dish

• 1 new single edge razor blade

• 1 marking pen

Teacher Preparation

CAUTION-WORKING WITH ULTRAVIOLET LAMPS. Short wave ultraviolet light can be extremely harmful to eyes and skin. Always be sure the lamp is facing away from the eyes of the worker. NEVER look at the light when it is turned on. Special ultraviolet protection goggles should be worn when working with the light. A good way to avoid damage is to set up experiment in the hood. Be sure the light is turned off when placing or removing the worms under the light.

Lethal exposure to the short wave ultraviolet light must be established before doing the research. I used a mineral light withs a 4 watt UV lamp that was 115 volts, 0.16 amps and emitted 254nm waves. Other sources of UV lights are the goggles' cabinet (used to sterilize the goggles), grow lights and UV lights from pet stores (used to find urine stains on rugs).The lethal exposure was 45 seconds at a distance of 24 cm.

To determine the lethal exposure:

1. Set up the lamp n a ring clam so that the light shines down at the base.

2. Place a piece of filter paper in the top of a 5cm petri dish and moisten with spring water.

3. Select a worm from the culture with a ppipette and place it on the filter paper. Pipette out excess water.

4. Examine the worm under the microscope and note any abnormalities.

5. Place petri dish with the worm under the UV light. Turn the light on and time the exposure.

6. At the end of the exposure time, turn the light off and remove the dish.

7. Place the worm in the culture dish well with the pipette. Fill the well with spring water.

8. Repeat the steps 1-7, changing the exposure time by 5 second increments.

9. Set up a control that is not exposed to UV light.

10. Cover the deep well culture dish of worms and check them in 24 hours.

Once the lethal exposure time has been determined, many areas may be investigated. Below are some directions the research could take:

1. Does being exposed to sublethal dose of shortwave UV light affect the regeneration time of the worm? Does it affect the regeneration time of different parts of the worm differently? (Will the tail be as affected by UV light as the head?)

2. If a worm is under stress from being cut in half, will the stress change the lethal exposure time?

3. Will a sublethal dose given to a worm in the middle of regeneration affect the type of regeneration?

4. Examine worms damaged by UV light under the microscope. What processes appear to be breaking down?

Extensions/Variations

1. Compare the survival of Lumbriculus sublethal dose to other type of worms such as the earthworm or tubiflex.

2. Run the same experiments using long wave UV light. How does exposure to this light affect regeneration?

3. Does the light used in goggles cabinets to sterilize the goggles have the same effect?

About The Author

Kay Widmer is a biology and ecology teacher at Hopewell Valley Central High School in Pennington,New Jersey. Kay can be contacted at Hopewell Valley High School, Pennington Titusville Road, Pennington NJ 08534 or by e-mail at widmer@pluto.njcc.com

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