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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.

a b s t r a c tThe behaviour of talitrids, being a local adaptation to beaches, is known to be related to environmental stability. The use of behavioural responses of resident populations as bioindicator of shoreline stability has been tested under various conditions, including after soft and hard engineering actions to stabilise eroded beaches. Port structures likely have impact on sediment longshore transportation and shoreline stability. The question was whether talitrid orientation behaviour could be proposed as bioindicator of impacts also for sandy bays of limited extension and highly used for recreation, such as those in the vicinity of touristic port structures. Orientation experiments were carried out on a set of sandy beaches of different extension and morphology, each of them in the vicinity of a touristic port, across the Mediterranean coasts. The protocol included field orientation tests of populations of talitrids, then analysed in terms of orientation precision seawards (considering sun compass orientation as the most locally adapted behavioural mechanism) in different seasons (before and after the touristic season) and times of day. The populations from more protected (either naturally or artificially) headland-bays showed a higher precision of orientation with respect to the shoreline direction than those from extended beaches, more subject to changes in longshore sedimentary transport as consequence of natural and human activities. The distance from the port and touristic pressure had no influence on talitrid orientation. An important stabilising factor for the sandy beach ecosystems, including talitrid populations and their behavioural adaptation, appeared to be the presence of seagrass banquette. The behavioural data point out that biotic information proceeding from local animal populations linked to beach sediments may complement sedimentology data and allow scaling the impacts occurring on a developed coastline. This becomes particularly relevant when considering interdisciplinary approaches to monitoring strategies.

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