Thermal acclimatization does not affect the resting activity of type T1 trichobothrium in the fi rebug (Pyrrhocoris apterus; Heteroptera)

Abstract

Firebugs (Pyrrhocoris apterus) pass through the winter in adult state. They undergo a series of physiological changes in order to increase their capacity to survive at low ambient temperatures. Nevertheless, even during winter their body temperature can rise up to 28 °C for a few hours on a sunny day, which is comparable to summer conditions. To establish the impact of cold acclimatization on the function of mechanoreceptors, the resting activity of T1 type trichobothria warmed up to 20 °C is compared in cold and warm acclimatized animals, as well in animals acclimated to laboratory conditions. In cold acclimatized animals the mean resting activity is 3300 imp/min (SE 90, n=13), in warm acclimatized 3400 imp/min (SE 60, n=15), and in animals acclimated to laboratory conditions 3700 imp/min (SE 130, n=17). The similar trend is observed in the variability of inter-impulse time intervals. The mean coeffi cient of the interval variation is in both cold and warm acclimatized animals 0.28 (cold SE 0.013, n=13; warm SE 0.010, n=15), and in animals acclimated to laboratory conditions 0.33 (SE 0.012, n=17). These data show negligible differences between the three groups. We can conclude that the resting activity of type T1 trichobothrium remains limited to a narrow range, regardless of the phase of the acclimatization process.