Introduction :

1. Introduction: What is the effect of a depressant on a Lumbriculus variegatus? This experiment is to test the pulse rate of a Lumbriculus variegatus with a depressant. The Lumbriculus variegatus can also be called the Blackworm, California Blackworm, and a Mudworm. Blackworms are commonly used in experiments because its skin is transparent. Transparent means you can see through the organism. Also, Blackworms live in shallow water therefore; they are easy to get ahold of. A depressant is any drug that slows down the reactions and normal functions of the nervous system. Some examples of short-term effects are the decrease in blood pressure, drowsiness, fatigue and confusion • Materials: • Two dissecting dishes with 10 worms each, small specimen cups, pipette, well slide, cover slip, depressant water, plain water, microscopeand stopwatch. Variables: Independent: Depressant Water Dependent: Pulse Rate Constants: Species of worm, well slide, temp. Control: Worms kept in plain water Effect of a Depressant on LumbriculusvariegatusBy: Monica Benjovsky and Kellie O’HearnReference: www.eeob.iastate.edu/faculty/Drewesc.htdoc Procedure: Step 1: With clear pipette retrieve five Blackworms from the plain water dish, and five from the depressant dish Step 2: Once back to the work station place one at a time with pipette, a Blackworm on the well slide. Step 3: Under 10 x magnifications, for one minute, record the pulse rate of the plain water worm, after tested place in finished dish. Do the same for the depressant worms. Step 4: Calculate the mean/average and median for both groups. Step 5: Keep your 10 worms in a separate container until your class is done. Conclusion: Our results did not support our hypothesis because the mean of the depressant water was 26.5 and the median was 26. The mean of the plain water was 20.4 and the median was 22. We expected the depressant water to decrease the pulse rate of the worm. However, the worms may have been frightened from our experiment, being moved from dish to dish. It may have interfered with our results because it increases their pulse rates. To improve our experiment, we could do more trials. Hypothesis: If Blackworms are placed in depressant water the pulse rate will be slower than those Blackwormsplaced in plain water. Results: We found that the mean for the depressant water was 6 pulses higher than our plain water which was not what we expected.