The effect of depressants on the heart rate of Lumbriculus variegatus By: Zachary Beecher Brendan Beecher Introduction: Lumbriculus variegatus, better known as a black worm, is a unique creature. They are used for pulse rate testing because they have transparent skin which allows one to easily observe it’s closed-circulatory system. Black worms are commonly found in shallow bodies of water such as marshes, ponds, or lakes. This experiment is testing the effects of depressants on the worm’s pulse rate. Our group made the hypothesis that if a worm lives in depressant water, then it will have a slower pulse rate than a worm living in plain spring water. Results: We found that the difference between the mean of both the plain spring water and of the depressant water is 5.8. Methodology: Get 5 worms from the plain and depressant water. Place them in the well slides with water. View them one at a time with the microscope, observe and record the pulse rate of all worms. Draw a conclusion to prove or disprove the hypothesis. Place the worm in a cup with water and then return the water. Materials: Well slides, spring water, depressant water, stimulant water, blackworms, microscope, cover slips. Discussion: We can conclude that the depressants in the water do, in fact, decrease the pulse rate of each worm. The blackworms in the depressant water have a slower heart rate than the ones in plain water. The depressants in the water slow down the pulse rate of blackworms. Our results support our hypothesis. Trial Plain Depressed 1 24 13 2 17 11 3 20 14 4 19 5 23