Diurnal activity of terrestrial arthropods in the High Arctic

At high latitudes, where the sun does not set over the horizon for a significant part of the summer, living organisms cannot regulate diurnal rhythms on the basis of photoperiod. In such regions, are other factors acting as zeitgebers or are the animals in these regions arrhythmic? The objectives of this study were to determine whether diurnal rhythms of locomotor activity are pronounced in model groups of terrestrial arthropods under natural conditions of constant light and to determine whether factors such as light, temperature, humidity, and wind influence this activity. Using pitfall traps, we have studied the diurnal activity of springtails, soil mites, dipterans, spiders, and beetles on Shokalsky Island, Kara Sea, Western Siberia (72.92°N 74.33°E). It was revealed that the continuous light regime in the Arctic does not eliminate the daily periodicity of activity of terrestrial arthropods. Periodicity was observed both at the whole community level and at the level of model groups and species. For the majority of the taxa studied, there was a daily peak of activity that occurred in the first half of the day. The general rhythm observed in different taxonomic groups indicates that the activity is regulated by some external factors. Although the rhythms identified apparently correlate with light level, temperature, and thermal preference, it remains difficult to determine the leading factor driving activity in the field.