Lumbriculus variegatus, also known as blackworms, have a dorsal blood vessel that acts as a peristaltic pump— pumping oxygenated blood through the closed circulatory system of the worm from the posterior to the anterior end (Halfmann, et al. p 1). Numerous pulsation waves can be seen moving along the worm and are easily observed as a result of the blackworm’s transparent bodies and noncomplex physiology. Because the blood vessel pulsation rate in blackworms is regulated by the nervous and endocrine systems— and many drugs can have an affect on these systems— several experiments have been performed involving the pulsation rates of blackworms in the presence of certain chemicals (Bohrer, 128). These experiments suggest that exposure to chemicals such as caffeine and nicotine can affect the organ system functions of the blackworm— resulting in an increase and decrease in pulsation rates. Specifically, it has been suggested that because caffeine works through countering the effects of inhibitory neurotransmitters, the blood vessel pulsation rate is increased in blackworms when exposed to this treatment (City College Manual, 47, center). And, because nicotine mimics the effect of the natural neurotransmitter, acetylcholine, higher and lower concentrations of …show more content…
The various extracts of caffeine found in coffee, decaffeinated coffee and tea had a similar effect on the rate of pulsation in the blackworms as that of caffeine. Further, the extracts of nicotine found in cigars and cigarettes had a similar effect on the rate of pulsation in the blackworms as that of nicotine. Because coffee, decaffeinated coffee and tea have caffeine in them, they also increase the rate of pulsation in the blackworms. Similarly, because cigars and cigarettes contain low concentrations of nicotine, they will act as a depressant— decreasing the pulsation rate in the