Tetrahymena cells are unicellular predatory ciliates that produce both sexually and asexually. It is an excellent laboratory model because it possesses certain single cell advantages that are beneficial in the laboratory, while also sharing many genes with us multi-cellular animals (Cole 2000-2013). One interesting quality of the Tetrahymena is the way in which they feed. They feed in a process called phagocytosis, which results in the creation of small food vacuoles within the cell membrane (Coyne 2011). For the control group of this experiment the Tetrahymena cells were fed India ink and allowed to feed. Immediately after and then every five minutes for twenty minutes a random sample of Tetrahymena cells were taken and added to 50ul of glutaraldehyde, killing the cells without damaging the tissues. Once mixed, the Tetrahymena were put under a microscope and then ten randomly chosen cells had their black food vacuoles counted. The counts were averaged and the standard deviation calculated. Tetrahymena not randomly chosen were excluded from the experiment. For the experimental group the same exact procedure was followed, except for that initially along with introducing India Ink to the Tetrahymena we also placed 1ul of serotonin into the culture. We still took food vacuole counts of 10 randomly selected cells every five minutes for twenty minutes using the technique described in the control group procedure. In this experiment we decided to test the effects of serotonin on Tetrahymena food consumption. Based on previous experiments we are aware that serotonin stimulates the consumption of nutrients in Tetrahymena cells, therefore we hypothesized that the addition of the serotonin would lead to an increase in the number of food vacuoles observed compared to the amount observed in the control trials. With this being our hypothesis we hoped to find results that lead to higher vacuole count means for the group treated with serotonin, then the control group at all time points.
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