1. The Effects of a Stimulant on the Pulse Rate of Lumbriculus Variegatus By: Ryan Reed and Olivia Neidert Introduction: Lumbriculus Varigatus, also known as the Blackworm, is a model organism that is very useful in laboratory experiments. The freshwater oligochaete has a body wall that is transparent, which makes it easy to observe blood vessel pulsations and circulation patterns inside the worm. This opens up the door for a number of experiments, including pulse rate testing. Charles D. Drewes observed the effects of chemicals on the Blackworm. He explained that oligochaetes make great subjects for toxicity testing since they are important parts of aquatic ecosystems and food chains. Also, certain freshwater species like Lumbriculus Variegatus have been used in the past for studying toxicity effects. For this lab, we tested the effects of a stimulant on the pulse rate of the Blackworm. Hypothesis: If the worm is immersed in the container with the stimulant, its pulse rate will be higher than the worms in the plain water. Independent Variable: The water containing the stimulant. Dependent Variable: The pulse rate of the Blackworm. Materials: Water, containers, stimulant, Blackworms, recovery bowl, microscope, pipette, thermometer. Methodology: First, we had to set up our microscope to make sure it was working. Next, we had to get a worm from the stimulant container, put it on the slide, and place it under the microscope. Then we had to count the pulse rate of that worm for thirty seconds, and multiply it by two to get pulse/min. Finally, we had to repeat these steps ten times (not step #1). Drewes, CD. 2003. A toxicology primer for student inquiry: Biological Smoke Detectors. The Kansas School Naturalist, Emporia State University, 50(1);3-14 Results: Because we chose a stimulant, our thoughts were that the pulse rate of the Blackworm would be higher than normal. As the graphs clearly state, our data supports our initial hypothesis. Although most of the pulse rates for the Blackworms containing the stimulant were higher than normal, there were a few that remained at a lower level than expected. There was even a pulse rate that was below normal. In that case, we had to eliminate that trial in order to provide more accurate results. For the Blackworm without the stimulant, the average pulse rate was 22.4 pulse/min, while the median value was 22 pulse/min. However, as expected, the average and median values for the Blackworm containing the stimulants were significantly higher, with the average being 26.8 pulse/min, and the median being 26 pulse/min. In order to acquire more accurate data, it would be necessary to incorporate more trials for both the worm without the stimulant, as well as the worm without the stimulant. These extra trials would also provide more comparable graphs which would aid in the analysis of the collected data. Conclusion: Although we did get the results that we were hoping for, it wasn’t as easy as we initially thought it would be. First off, we didn’t take into consideration how difficult it would to count the pulse rates of a worm that had been exposed to a stimulant. The worm was constantly moving around, so several times we had to get either a larger or smaller worm to fix the problem. Secondly, some of the worms were darker than others. This made it even more difficult to get a count on the pulse rates. As mentioned before in our Results, we did have one trial that was below the number of pulse rates that we needed. We wanted most if not all of the trials to be above 23 pulse/min, but that one came out at 18 pulse/min. That was why we decided to eliminate it. Overall though, our ending results did agree with our primary hypothesis. It would be possible to gather more accurate data by adding more trials to the experiment for both the worm without the stimulant, and the worm with the stimulant.