The response of isopods towards temperature, humidity and light

1. In the foregoing study, the response of isopods to the interaction of three environmental factors: temperature, humidity and light, was analysed. This resultant behaviour is the main ecological factor keeping the animals in favourable microhabitat. 2. A. vulgare is positively thermo-active at all temperatures studied. This reaction is not changed either by light or humidity. The main mechanism is speed of locomotion rather than activity. 3. V. arizonicus is negatively thermo-active at high temperatures, i.e. the increase in temperature is not followed by a corresponding increase in activity or speed. 4. A. vulgare is positively hygrokinetic at low and medium temperatures. At high temperatures light may affect this reaction by changing it to negative hygrokinesis. The main mechanism involved here is the change in activity and not the speed. 5. V. arizonicus is positively hygrokinetic at low and medium temperatures, provided the humidity range is medium. At high temperatures this changes to a negative hygroreaction. The main mechanism is again the activity and not the speed. 6. The saturation deficit does not seem to play a role in the humidity reaction of V. arizonicus. The response seems to be mainly towards the gradient in relative humidity. The response of A. vulgare is probably different but it is not clear whether it was the saturation deficit that affects the hygroreaction, or thermo-activation due to high temperatures. 7. A. vulgare was found to be positively photokinetic at low and medium temperatures. This response is not affected by humidity. At high temperatures the animal may become negatively photokinetic depending on the humidity conditions. The mechanisms are the speed of locomotion, and activity rate defined by the number of shifts from one zone to the other alternative. 8. V. arizonicus is mainly negatively photokinetic except at high temperatures, and when the humidity is high in the shade, then the animal may become positively photokinetic. The main mechanisms are speed and activity. 9. The photoreaction of both species changes during hours of the day with less response towards photic stimuli towards the evening.