Hourly and monthly variations in the surface activity patterns of Hemilepistus reaumurii in arid environments of Tunisia
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Life in desert ecosystems drives animals to adapt their surface locomotor activity according to environmental conditions. In this study, the hourly and monthly variations in the surface activity patterns of the terrestrial crustacean Hemilepistus reaumurii were investigated. The surface activity of H. reaumurii at the population scale was observed by collecting the hourly active individuals from the sunrise to the sunset of the studied day in each month of 2013 in the Bchachma locality, Tunisia. The collected active individuals were put in perspex boxes (on which we labeled the hourly time interval in which the individuals were collected) in the field and then transported to the laboratory for analysis. Individuals were counted, sexed and measured in the laboratory. Despite desert conditions in the studied site, H. reaumurii was characterized by a diurnal surface activity, showing a bimodal pattern during the warm months (i.e., May to October). However, it exhibited a unimodal surface activity pattern in the cold months (i.e., February, March and November). The surface activity was significantly correlated with sunrise and sunset. Moreover, a significant quadratic effect of temperature on the surface activity of H. reaumurii was observed. Furthermore, the study showed that the most important surface activity was recorded in March. The daily exploitation of the temporal niches was significantly different as a function of months. The body size of males were larger than that of females, and the body size of active individuals would change with months. All these behavioural changes in the surface activity represent an adaptive strategy of life in the arid environment.
Keywordsdiurnal activity variation pattern aboveground activity desert isopod temporal niche Hemilepistus reaumurii Tunisia
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This work was supported by the University of Tunis El Manar. We wish to thank Mrs. Sabiha KHIARI-AYARI, Ms. Nada AYARI and Mr. Assad ABIDI for their important contribution in accomplishing the field work of this study. We also wish to thank Dr. Julian REYNOLDS for constructive remarks and English revision of the manuscript. We also thank the two anonymous reviewers for their helpful comments on this paper.
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