Hourly and monthly variations in the surface activity patterns of Hemilepistus reaumurii in arid environments of Tunisia

Abstract

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 was larger than that of females, and the body size of active individuals changed with months. All these behavioural changes in the surface activity represent an adaptive strategy of life in the arid environment.

Burrowing detritivores regulate nutrient cycling in a desert ecosystem

“…They then leave their natal burrows, form pairs and establish new family burrows [32,33]. Foraging activity peaks in the hot and dry summer months, where isopods forage aboveground for plant litter and BSC during a short time window of 1–2 h after dawn [34]. During this time, isopods feed aboveground.…”

Daily and seasonal time partitioning in surface activity of Porcellio albinus (Isopoda, Oniscidea) in the arid region of Zarat (Gabes, Tunisia)

“… Porcellio albinus exhibits a different activity rhythm compared to H. reaumurii , although the two species are from similar guild of burrowing species and occupy the same habitat in Zarat. Hemilepistus reaumurii shows diurnal surface activity ( Cloudsley-Thompson 1956a ) from February to November and remains inactive during December and January ( Ayari et al 2018 ). Nocturnal activity as observed in P. albinus is conventional for the majority of terrestrial isopods, while diurnal activity of Hemilepistus is an evolutionary novelty.…”

“…At night they appear from their hiding places and are able to wander in dry areas where they are not usually found during the day. In general, this is true for the majority of terrestrial isopods, but there are exceptions such as Armadillidium vulgare Latreille, 1804 and Hemilepistus reaumurii (Milne-Edwards, 1840), which are more resistant to desiccation compared to other species ( Edney 1951 ; Ayari et al 2016 ), and can appear out of their burrows in full sunlight ( Cloudsley-Thompson 1951 ; Ayari et al 2018 ). Extensive and detailed studies on these activity patterns in different species of terrestrial isopods unravel species-specific activity patterns deviating from strict nocturnal activity.…”

“…For example, the semi-terrestrial burrowing isopod Tylos spinulosus Dana, 1853 shows activity along the beach depending on the tide ( Jaramillo et al 2003 ); Armadillidium vulgare is active in the morning hours in open habitats ( Cloudsley-Thompson 1951 ) and the forest species Porcellium conspersum (C. Koch, 1841) is active mainly during the day in spring (Tuf and Jeřábková 2008). Hemilepistus reaumurii occurs in desert regions and is active mostly during the hours of daylight with a bimodal pattern during warm months and a unimodal surface activity pattern during cold months ( Ayari et al 2018 ). The daily epigeic activity of terrestrial isopods depend mainly on the light-dark regime and to a lesser extent on air humidity and temperature ( Tuf and Jérabkova 2008 ).…”

Metamicrobiome-driven homeostasis of nutrient recycling

“…Foraging activity by termites (Macrotermes sp.) and desert isopods (Hemilepistus reaumurii) peaks during the hot and dry season [52,53], which can lead to a proportional increase in macrodetritivore-driven recycling during drier periods relative to the free-living microbiome [54,55] (Fig. 4D).…”