The effect of temperature on the speed of locomotion in <i>Caenorhabditis elegans</i>

Abstract

Changes in environmental temperature are known to have strong impacts on the biochemistry and behaviour of ectothermic organisms such as Caenorhabditis elegans. In this experiment, the effect of temperature on the speed of locomotion of N2 wild-type C. elegans at 12.0°C, 15.0°C and 20.8°C (control) was studied. The total distance travelled along an agar-filled petri dish per unit time was calculated for each replicate, and subsequently converted into speed. A positive correlation between temperature and the average speed of C. elegans’ locomotion was found. Significant differences between the mean locomotion speeds were found to exist between select temperatures (ANOVA, p=0.002). Specifically, the mean speeds of C. elegans’ locomotion were significantly slower at 12.0°C (3.8 ± 1.6 mm/min) and 15.0°C (5.2 ± 1.5 mm/min) than that at 20.8°C (8.6 ± 1.7 mm/min) (Tukey Kramer HSD, 12.0°C vs. 20.8°C p=0.004 and 15.0°C vs. 20.8°C p=0.03). However, the differences in mean locomotion speed at 12.0°C and 15.0°C were not statistically significant (Tukey Kramer HSD, p=0.48). Treatment temperatures below the control temperature could induce a cold shock response in C. elegans where TRPA plasma membrane channels prevent Ca²⁺ from exiting the cell. In motor neuron cells, the increased intracellular [Ca²⁺] reduces the cell’s excitability; whereas in muscle cells, high intracellular [Ca²⁺] results in decreased ATP availability. Both scenarios reduce C. elegans’ muscle contractions and consequently, their locomotion speed at temperatures below their optima. Overall, results from this study give insight into how the competitive abilities of these and other nematodes may be impacted by global temperature changes.