**6. Future prospects**

a geographical distribution which depends on many ecological factors mainly climatic and orographic and of less importance edaphic. All of them were distributed south of the Tunisian Dorsal; the distribution of both xeric species *P. simulator* and *P. buddelundi* was limited, in the North, by the 500 mm isohyets. The distribution of *P. olivieri* was restricted to arid environments, while the rare species *P. albicornis* and *P. albinus* tolerate remarkably high temperatures and were able to reach the Sahara. Woodlice showing comparably effective adaptations to desert environments are *H. reaumurii* [26] and *Venezillo arizonicus* [77]. The latter two species possess protection against water loss through the cuticle which corresponds to a thicker and more calcified cuticle, thus reducing water evaporation in arid environments [53] and indicating that permeability to water has been reduced during adaptation to habitats with periodically or permanently low water availability. These physiological adaptations were, however,

To survive in the harsh conditions of the desert and escape the danger of desiccation, the *Porcellio* survive the high temperature during the day in summer and autumn, either by vertically migrating (*P. buddelundi*, *P. simulator*, *P. olivieri*, and *P. albicornis*) or in a burrow which *P. albinus* dig in loose soil at any time of the year unlike *H. reaumurii* [26] who dig new burrows only in early spring. The maximum density of burrows, in nebkhas, was recorded in the southern sector to avoid the main wind direction [23]. *P. albinus* showed no daily activity; all year long it is a strictly nocturnal species. Individuals whose size is more than 8 mm started their activity after dusk to forage and return to their shelter before dawn. This nycthemeral rhythm of *P. albinus* is regulated by the rhythmic and natural variations of the duration of the scotophase. The circadian rhythm in *P. albinus* is probably generated by an internal clock that is synchronized to light-dark cycles and other cues in an organism's environment; this intrinsic timer was apparent in *Tylos europaeus* [78] and *H. reaumurii* [79, 80]. Nocturnal activity of *P. albinus* was correlated to a lower evaporation rate. In burrows, *P. albinus* breed and take care of their offspring for about 2 months [22]. Given the importance of a burrow for this species, the sand, scraped from the burrow and piled outside, when the member of a family started their activity, was used to close the burrow during the day probably as an antipredatory strategy. In addition, *P. albinus* used mechanisms similar to those found in *H. reaumurii* [55, 81], using combination of celestial mechanisms and the sand scraped from the burrow to relocate the burrows after foraging [44]. Burrows of *P. albinus*, in nebkhas of Zarat area, showed a simple or complex tunnel with one nesting chamber in its deep part for the first and with two nesting chamber for the second. *P. albinus'* burrow length reached its

In addition to behavioral adaptations, the pre-desert and desert species of *Porcellio* have developed reproductive strategies that allow them to better succeed in the colonization of arid environments. The study of the reproductive phenology of the populations of the two *Porcellio* species from pre-desert ecosystems in Tunisia allowed to bring new fundamental knowledge on the dynamics of these populations as well as on the reproductive traits of the xeric *Porcellio* species *P. albinus* and *P. buddelundi*. The reproduction of these two iteroparous *Porcellio* was characterized by two breeding seasons: the most important one in spring and the other in autumn distinctly separated by a sexual rest phase [22, 24]. This reproductive phenology differs from that of (1) mesic species such as *P. variabilis* [33, 82], which generally shows a breeding period spread over several months followed by a sexual rest and (2)

insufficient for coping with the harsh conditions of desert environments.

maximum in September.

46 Community and Global Ecology of Deserts

Future prospects, which could be considered from our research and have led to the following questions, are as follows:

• The reproductive phenology of desert *Porcellio* species other than *P. buddelundi* and *P. albinus*, such as *P. olivieri* and *P. simulator*, and their reproductive strategies.

• The behavioral aspect of reproduction in pre-desert and desert species from arid environments: the choice of the sexual partner, sexual conflicts, polygamy, parental care, etc.

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The susceptibility of *P. albinus* to temperature rise and moisture decline makes this terrestrial isopod an appropriate biological model for examining its potential responses to climate change. This line of research could be considered in the context of global climate change such as the study in microcosms of the effects of changes in temperature and relative humidity on the activity, aggregation, and survival of *P. albinus*.
