Effect of starvation on phototaxis and geotaxis of collembolans

The effect of starvation on the behavioural response of three common hemiedaphic collembolan species Hypogastrura assimilis (H. assimilis), Isotoma notabilis (I. notabilis) and Proisotoma minuta (P. minuta) to light was examined. Adults of all the three species were shown to respond negatively to light, as approximately 40% of the H. assimilis, 20% of the P. minuta and 30% of the I. notabilis were recorded in the light area of the arena. However, when adults of H. assimilis were starved, they became increasingly attracted to light with increasing length of the starvation period and after 5 d of starvation, 83% were recorded in the light area. Starvation was not observed to change the behaviour of the other two species. Following these experiments, the effect of starvation on the response to gravity was tested for H. assimilis by placing individuals on a 15° slope. At day 0 of the starvation period, half of the specimens were recorded to move down the slope whilst the other half remained in the middle compartment; none were observed to move upwards. After 1 d of starvation, the proportion of collembolans moving downwards had reduced to 17% and remained low for the following 4 d of starvation. The proportion of collembolans that moved upwards increased significantly during the starvation period from 0% on day 0 to 28% on day 5 of the starvation period.