Effect of different concentrations of copper sulphate on the speed of Caenorhabditis elegans

Al-Haqq N. Govani, Alan H.S. Lam, Margarita Pacis, Marina T. Tan

Abstract


The free-living parasitic nematode, Caenorhabditis elegans, is subject to a variety of chemicals in the wild, which have been shown to affect their behaviour (Bargmann et al. 1993). We exposed the roundworms to three different concentrations of a known repellent, copper sulfate (Troemel 1999, Wang and Xing 2008), and observed their response. We expected that the repellent would induce a negative chemotaxis such that the nematodes would move away from a repellent source at higher speeds when exposed to higher concentrations. We created a concentration gradient for our each of our experimental conditions by placing 100 uL of 5.308 mmol/L, 10.616 mmol/L and 15.925 mmol/L concentrations of CuSO4 in the centre of each Petri dish and allowed it to diffuse for three hours. We then placed three nematodes equidistantly around the point source of CuSO4 and recorded their movement for four minutes, taking note of their behaviours. From the video recordings, we measured the distance each worm travelled, and then calculated and compared the velocities of the nematodes. The nematodes moved an average speed of 0.24 ± 0.11 mm/s in water, 0.15 ± 0.05 mm/s in 5.308 mmol/L CuSO4, 0.10 ± 0.01 mm/s in 10.616 mmol/L CuSO4, and 0.06 ± 0.00 mm/s in 15.924 mmol/L CuSO4. Contrary to our prediction, the data showed an apparent trend in which the nematodes moved slower as the concentrationof CuSO4 increased. The worms moved at a significantly slower speed at the highest concentration.


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