Ciliates are unicellular protists that are easily identified by their cilia – small hairlike structures. They use their cilia for locomotion and feeding by producing a current to sweep in bacteria and other food particles. Ciliates take up food by phagocytosis (Luan 2012). This is stored in food vacuoles which are used to transport the food (such as bacteria, yeast and small algal cells) throughout the cell. Food vacuoles are lipid-like vesicles that have membranes to allow food particles to be taken up (Jacobson and Andersen 1994). Ciliates have an optimum temperature of around 28 °C to 30 °C (Luan 2012) and are commonly found in both fresh and salt water. The specific protist used in this experiment was Spirostomum sp. Spirostomum sp. have the fastest body contraction in any living cell. In six to eight milliseconds it can contract up to 25 % of its body length (Egmond 2002). The aim of this investigation was to show the effects of sudden environmental stress on the number of food vacuoles within ciliates.
Materials and Method
One drop of carmine particles was added to each tube of ciliate culture containing Spirostomum. A drop of this culture was put on a slide and examined under x 10 objective. The number of food vacuoles within the ciliate was counted. The other culture was left at room temperature for ten minutes. During that time, 5 grams of salt was added to a cup of ice which reduced the temperature to -5 °C. Next a microtubule filled with 0.5 ml of water was put into the ice to mimic the ciliate culture and check the temperature. After that, a sample of the ciliate culture was put onto a microscope slide with a drop of methyl cellulose to slow down the speed of the ciliates. A coverslip was put on and the sample was observed using the x 10 objective lens. The ciliates were located and the food vacuoles were counted in five of the ciliates. If necessary the x 40 objective lens was used. One of the tubes of the ciliate culture was put into the ice mixture and left for five minutes. Then this was then put onto a microscope slide with a coverslip on and examined under x 10 objective. The number of food vacuoles were counted in five ciliates and recorded. This data was then collaborated by the class and the means were calculated.
Results
Chart 1:
There was an identifiable relationship with the temperature and the amount of food vacuoles in the ciliate cells. When the cells were at -5 °C there were less food vacuoles (around five per cell) than when the temperature was at 20 °C (around six food vacuoles). Cells at the beginning of the experiment had less than both of the other cultures with around four food vacuoles per cell. However, the standard error bars overlap between the ciliates at 20 °C and the ciliates at -5 °C, this shows there is no significant difference between them. The standard error for the ciliate cells at the beginning of the experiment overlap with the -5 °C ciliate cells, showing no significant difference between them.
Discussion
Table 1 shows that as the temperature decreased so did the number of food vacuoles within the Spirostmum sp. There was the biggest number of food vacuoles within the ciliate cells at 20 °C, this coincides with the findings of Luan (2012). Where they concluded that the optimum temperature of ciliates was between 28 °C and 30 °C. Their study showed a decrease in food vacuoles below these temperatures and therefore a decrease in metabolic rate. The class findings additionally agreed with Chan, Pinter and Sohi (2016), where they determined the effect of temperature and other factors, such as time, on the number of food vacuoles. It was suggested that temperature had an effect on the membrane fluidity and the rate of protein synthesis. This implies that bringing the temperature below optimum rate for Spirostomum sp. could prompt a slower enzyme rate within the cell, leading to an overall slower metabolic rate. This could also be linked to the efficiency of phagocytosis and the uptake of food, meaning as there is less food being taken up, there is a lesser need for food vacuoles to transport and contain food. This supports the results in Table 1.