Morphological and reproductive variability in Porcellionides pruinosus (Brandt, 1833) from Tunisia (Isopoda, Oniscidea)

Six populations of Porcellionides pruinosus from different geographical localities, belonging to five bioclimatic areas in Tunisia, showed a variable reproductive behaviour. Some populations presented seasonal reproduction while other ones exhibited continuous reproduction. Populations with seasonal reproduction showed two distinct breeding peaks. The first peak in spring was characterized by large gravid females with the greatest fecundity and fertility, the second one, in autumn by small females, exhibiting low fecundity and fertility. Females are able to produce two or three broods per reproductive cycle in populations showing seasonal reproduction, and between four and five in continuously breeding populations. Although oscillating throughout the year, the sex ratio was female-biased in most populations, and differences were highly significant in populations with continuous reproduction. Analysis with the scanning electron microscope showed important phenotypic variation between the populations studied in the form of the pleotelson and its lateral borders that seem to exhibit reliable differences between the specimens examined. These features can be used as discriminating characters between populations of Porcellionides pruinosus.