Effect of temperature on the negative geotaxis response in Drosophila melanogaster

Abstract

In our experiment, we used the species Drosophila melanogaster to further elucidate the basis of a known behavioral trait, geotaxis. Drosophila are negatively geotactic; they move against the pull of earth’s gravity. Using lab-raised flies, we investigated the sensitivity of this attribute to a range of temperatures. Four treatments of 13°C, 18°C, 28°C, 33°C, and two control treatments of 22°C and 23°C, were administered over the course of two lab periods. Ten replicates per treatment were performed, each comprising five males and five females. We recorded the time individuals took to move a distance of four centimeters in an inverted test tube, when exposed to a specific temperature. We found that at 18°C, Drosophila melanogaster exhibit the most pronounced negative geotactic response. This temperature was the only significant value found in our data; the differences among the other treatments were not statistically significant. The optimal range of temperature for D. melanogaster has been reported as between 23°C to 25°C; this does not agree with our finding that 18°C produces the strongest negative geotactic response, and leads us to consider reasons for this discrepancy.