The Effects of a Depressant on the Pulse Rate of Lumbriculus Variegatus By: Adryan Cheeseboro and Katie Mann Introduction We used Lumbriculus variegates, commonly known as the black worm for our experiments. The black worm's environment is shallow edges of ponds, lakes and marshes. Lumbriculus variegates is asexual and uses autotomy to split itself into different fragments. Each fragment will grow a new head or tail section. We chose to test this worm because the skin of the worm is transparent. The hydrostatic skeleton allows us to observe the fluid cavity inside the worm. The transparent skin of the worm also allows us to see the dorsal blood vessel pumping blood making it easier to count the pulse rate. The blood of the worm circulates in a closed system of vessels and capillaries and is pumped in rhythmic contractions. We tested the black worm's pulse rate while the worm was under the influence of a depressant. A depressant is know to slow down bodily functions, such as pulse rate, making the worm easy to test for this. Hypothesis If a depressant is added into the worms water their pulse rate will decrease compared to worms in spring water. Independent Variable- The added depressant. Dependent Variable- Black worm's pulse rate per minute. Control- Black worm’s pulse rate in spring water. Constant- The base of spring water in all containers that is used and the temperature of the water. Results- As we tested the pulse rate of the ten black worms, we found the average rate was 12.6. The average pulse rate of the worms in the spring water was 14.6; 70% of the black worms were under the average pulse rate when they were in the depressant. Procedure First we used a pipette to get a worm into the well slide, that was specially cut to hold the worm. Then we let the worm settle into the well for a couple minutes. We put the slide under the microscope, making sure to only turn on the light when needed. If left under the microscope for to long the worm may overheat; we kept the light usage minimal. We focused in on the mid-section of the worm to read the pulse rate. The pulse rate was read for a minute each time and when done with the worm, we returned it to a recovery bowl. We then repeated this with 10 different worms. Conclusion- When we were observing our data our results were just about similar to our hypothesis; the depressant would cause the heart rate to be lower. The significance of our results show that if this depressant or the similar chemicals to the depressant were to come into their environment, it would lower their heart rate. Further research that should need to be pursued would be to repeat the process and do a stimulant test. The things to change or include in future experiments would be use the same amount of worms in the spring water as the depressant for better results. Also to make sure you are giving the depressant to the worm the same time of day and the amount. McCarter. 2014. Let's put "LIFE" back into Life Science!, edublog. Drewes, CD. 2003. A toxcology primer for student inquiry: Biological Smoke Detectors, Kansas School Naturalist, Empire State Univerity, 50(1): 3-14.