Effect of season and sex on the locomotor activity rhythm of the desert isopod Hemilepistus reamurii

Abstract

ABSTRACT Freshly collected individuals of Hemilepistus reaumurii from the marginal zone of a salt lake in Bchachma (Middle of Tunisia) were seasonally housed in a controlled environment cabinet. The aim of this study was to investigate the effect of sex on the locomotor activity rhythm of this species. Locomotor activity rhythm of males and females of this species was recorded during each season under light-dark cycle (nLD) at a constant temperature of 18 ± 0.5°C. Results showed that both males and females of H. reaumurii exhibited a day activity in late winter and in spring and a crepuscular activity during the other seasons. Results showed also that the locomotor rhythms of males and females were controlled by an endogenous component with circadian period. Furthermore, locomotor rhythm was more stable and better defined in males than in females during spring under constant darkness. The most important locomotor activity time (α) was recorded in winter and spring whatever the sex. However, our finding demonstrated that males were more active than females in late winter. On the other hand, females were more active than males during spring. The variation of activity patterns according to the sexes and seasons is discussed.