This Stuff Makes Me Sick

Dawn Hancock and Linda Ellis

Overview:

Lab showing the effects of pesticides on Lumbriculus variegatus.

Biological Concepts:

Neurotransmission

Pesticides in environment

Relationship between nervous and vascular system

Relevant Units: Vascular System/Nervous System; Ecology: Pollutants in Water Sources; Impact of Humans on Environment

Class Time: one 55 minute period

Background Information:

Target Group: Biology I, Ecology , Physiology

Culturing Lumbriculus variegatus : Refer to Appendix I

Handling of Lumbriculus variegatus: Refer to Appendix I

Making Observation Slides: Refer to Appendix II

Caveat: This experiment has not been field tested but in the hands of the authors the worms showed a definite change in behavior. Also, Diazinon should handled carefully following instructions from the package label.

Diazinon Information: Diazinon is a non-systemic organo-phosphate insecticide used on home gardens and farms to control a wide variety of sucking and leaf eating insects. Diazinon has veterinary uses against fleas and ticks. 2.6 million pounds of Diazinon were used each year prior to 1983. Toxic effects of Diazinon are due to the inhibition of acetylcholinesterase. Birds are quite susceptible to Diazinon poisoning as are most fish. Diazinon has a relatively low bioaccumulation rate as compared to DDT. Diazinon seldom migrates below the top 1.3 cm in soil but can stay biologically available for six months under conditions of low temperature and low moisture. Diazinon has been detected in some water supplies.

Relevant Units: Vascular System/Nervous System; Ecology: Pollutants in Water Sources; Impact of Humans on Environment

Materials : (per student group)

2 Lumbriculus variegatus worms

petri dishes or other containers for worms

0.2 % solution of Diazinon

observation slide

plastic pipette cut to a large bore size

paper toweling wicks

dissecting microscopes

rubber band widget (refer to Appendix II)

distilled or spring water or dechlorinated tap water - amount necessary is dependent upon the containers for worms during treatment. Use enough to fully cover worms. For control of variables, it is suggested that teacher/class determine the amount to be used.

stop watch

Teacher Preparation:

Preparation Time: 45 minutes

Culturing Worms: Refer to Appendix I

Slide Preparation Time: About 1 h. With proper storage, these slides can be reused.

Extensions and Variations:

Students can use other environmental chemicals to determine effect on worms.

Assign students the problem of determining the concentration of Diazinon in their public water supply and relating this to usage by community. (This data should be available through local government if you teach in an urban area.)

Assign creative writing project: Day in the life of Lumbriculus variegatus from the point of view of the worm. Include a storm with run-off from nearby Diazinon treated lawns.

Resources:

Diazinon: Lawn and Garden stores; large supermarkets

Parafilm: any science supply company

Web Site: ExToxNet http://ace.orst.edu/info/extoxnet

About The Authors:

Dawn Hancock, Biology Teacher

P.L. Dunbar High School

5700 Ramey Avenue

Fort Worth , TX 76112

email: dhancoc@tenet.edu

Linda K. Ellis, Director of the Secondary Programme

The International School of Grenada

PO Box 744 St. George’s

Grenada, West Indies

email bmcs@caribsurf.com

NAME______________________________DATE:_____________PERIOD:_____

This Stuff Makes Me Sick!

Student Activity Sheet

Problem: The use of insecticides is critical to maintaining agricultural productivity. However, it is important to remember that these compounds may eventually find their way into our water supply. Depending on the stability of the compounds, their effects may be much more widespread than we realize. In this activity, you will discover the effect of a commonly used insecticide, Diazinon, on the aquatic worm, Lumbriculus variegatus. Diazinon remains biologically active in the environment for many months. In concentrations only 10 times greater than you will be using, Diazinon is lethal to the worms in just a few minutes.

Procedure:

• Obtain 2 worms from the culture station. Use a large bore pipet to gently remove the worms from the culture dish and place them in a Petri dish of distilled or spring water. Only one worm will be used, but keep the untreated worm to use for purposes of comparison. Observe the behavior of the worms before treatment.

• Return to your lab table and carefully transfer one worm to a slot in the worm-viewing slide. In this process you will also transfer a drop or more of water which you must remove, using the pipet and/or the paper towel. Only enough water to fill the slot should remain. Now your worm must stay in the slot in order to remain in water!

• Place this slide under the dissecting microscope and examine the worm. Note the movement of the blood in the dorsal blood vessel.

• Describe the normal "pumping" action of the blood vessel. Be sure to record your observations.

• Put some of the solution of Diazinon which your teacher has prepared into a Petri Dish. Be careful not to get the solution on your skin. Transfer the worm from the viewing slide to the solution. It should remain in the diazinon solution for 4-5 minutes. Observe and record its behavior during this time period.

• Transfer the worm from the dish to the worm-viewing slide, being sure to remove all the excess solution.

• Once again, observe the movement of blood in the dorsal blood vessel.

• As soon as you have made your observations, return the worm to the distilled/spring water to allow it to recover.

Observations

I. Make notes on the worm's behavior before treatment.

II. Describe the normal movement of the blood in the dorsal blood vessel.

III. What has happened to the worm after being exposed to Diazinon?

IV Discussion and Conclusions: Write a complete paragraph

explaining the significance of your data.

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