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Specimens of Porcellio variabilis coming from Tunisian populations were genetically and morphologically examined.

Oniscids inhabiting xeric habitats are of particular interest because these habitats may be one of the important agents for desert soil fertility. Although numerous studies have examined the relationship between the environment and population ecology in woodlice that live in mesic habitats, very little is known about these desert species. Tunisia is known for its arid regions south of the Tunisian Dorsal, habitats in which several species of terrestrial isopods are well adapted. Porcellio is the most widely represented within these habitats: their species richness reaches eight in arid bioclimatic stage. The most widespread of the Porcellio is P. buddelundi, and the least widespread is P. albicornis. Behavioral and reproductive studies carried out in Zarat and Matmata on the two species P. albinus and P. buddelundi showed that the xeric Porcellio species are mainly active at night and they shelter from the extreme heat and dryness of their habitats either in burrows they dig or by vertical migration. The reproductive pattern is seasonal with two breeding seasons. Life history traits allow P. buddelundi to be an r-strategist and P. albinus a k-strategist. The latter displays a fairly developed social behavior, which allowed him to be the most evolved of Porcellio.

Abstract:The breeding phenology and reproductive strategies of Porcellio variabilis were investigated, both in field and laboratory, in the population of Béja (North of Tunisia). P. variabilis Lucas, 1946 is characterized by a seasonal reproduction period followed by a sexual rest phase during November, December and January. Mean fecundity showed a great seasonal variation ranging between 29.612 eggs for females caught in the late summer, and 125.920 eggs for those collected in the spring. P. variabilis is an iteroparous species; females were able to produce one (95% of females), two (40% of females) or three broods (20% of females) during their reproduction period. The duration of the gestation period ranged from 34 days in the first brood to 14 days in the third one. Energy allocated to reproduction decreased from the first brood (26.29%) to the last one (4.618%). During the sampling period, eight cohorts were identified, each exhibiting a variable life span estimated around 6 months for cohorts born in early spring, and 12 months for those born in the fall. According to our present results and previous studies in another population of P. variabilis in Tunisia, we discuss factors of variability in breeding phenology in this species.