Stimulus Variegatus Lab Report

The Addition of Caffeine and Nicotine to the Circulatory System of Lumbriculus variegatus and the Effects on the Organism’s Pulsation Rate

INTRODUCTION Lumbriculus variegatus, also known as blackworms, are relatively small specimen. Their physiology is so simple that the organisms lack a respiratory system and heart. Henceforth, blackworms rely on diffusion in means of gas exchange through their tail segments and muscle contractions of the dorsal blood vessel (Laboratory Manual BIO 10200, p.69). The circulatory system of the blackworm is closed containing arteries, veins and a muscular pumping dorsal vessel which contracts enabling blood to be moved from the posterior end, where gas exchange occurs, to the anterior region, the head of the

Using a disposable plastic pipet, worms were transferred with a bit of spring water to the viewing chamber and given a few minutes to settle to their new surroundings. The viewing chamber was then placed under the dissecting microscope at the lowest power, which helped with focusing on the middle body region of the worm to measure pulsation rates. Using a stopwatch, the basal rate of the worm was obtained by counting the number of pulses that moved through a segment in a thirty second interval, this amount was multiplied by two to result in units of beats per minute. Three basal rates were recorded for each of the three individuals warms to calculate their mean rate. Worms A, B and C were then placed into separate containers containing the caffeine treatment solution. After allowing the worms to be treated for fifteen minutes, they were briefly rinsed and placed in the viewing chamber to measure their pulsation rate. This was done three times for each worm to calculate a mean rate for first level of treatment, 3.0 mM of caffeine. The same procedure was repeated for part II of the lab, however; a different set of three worms were treated with nicotine and all the means were collected to calculate the standard deviation of each