Population dynamics and reproductive aspects of Porcellio albinus (Isopoda, Oniscidea) of Zarat (Gabes, Tunisia)

Porcellio albinus is a nocturnal species inhabiting xeric habitats in Tunisia. Size distribution, population dynamics, breeding activity, fecundity, fertility, reproductive allocation (RA), and life span were studied to establish the reproductive strategy of a population of this species in the sandy coastal area of Zarat. Monthly sampling was undertaken between July 2012 and November 2013. The overall sex-ratio of P. albinus was female biased. The relative abundance of adults, much more representative than that of juveniles, might be the consequence of the absence of specimens less than 8 mm in size in all samples collected outside the burrows at night. Reproduction is seasonal in P. albinus with two breeding seasons, the first one from March to June and the second in September. Five cohorts were recruited per year, four during the spring and one during the fall. The number of eggs per female ranged from 13 to 67 and was positively correlated with female body size. Fertility varied from 5 to 39 mancae. Compared to other xeric species, RA was low to produce a brood, but high to release a single manca. The results provide a better understanding of the reproductive behavior of this terrestrial isopod, living under severe environmental conditions.