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The amphipodTalitrus saltator(Montagu 1808), diffused on the Mediterranean and Eastern Atlantic coasts, displays physiological and behavioural adaptations to life on sandy beaches. To avoid dehydration, sandhoppers burrow in moist sand near the water’s edge during the day in the warmest seasons. When displaced, they can navigate to this safe zone using a sun compass and several additional mechanisms, both universal and local, an adaptive behaviour named ‘zonal recovery’. In this study, we analysed the effects of several variables on the talitrids’ orientation behaviour to highlight the relevance of the local cues and analyse the behavioural variation with relation to the ecology of sandy beaches. In different seasons for 2 years, orientation experiments were made onT. saltatorsub-populations, at three sites of an extended sandy beach, differing in shoreline sedimentary dynamics; the main environmental, climatic and individual variables known to influence talitrid orientation were registered during each experimental session. The statistics of circular distributions were calculated and a multiple regression analysis adapted to angular data was performed, to highlight the scaling triggered by environmental conditions. The results showed that seasonal climatic variables played a primary role, adaptively modifying the sandhoppers’ behaviour. A significant interaction with the site (the chosen sites differed for sedimentary dynamics) was observed as well. A high behavioural plasticity appears to guarantee toT. saltatora good adaptation (both as abundance and geographical spreading) to life on sandy beaches, which are notably unstable environments. [ABSTRACT FROM AUTHOR]

The present paper reports on the first orientation experiments conducted on the strand-living beetle Eurynebria complanata (Linnaeus, 1767) (Coleoptera, Carabidae). The experiments were carried out from June to October 1988. Two different populations were used: one inhabiting a Tyrrhenian beach in Italy and the other a beach on the Atlantic coast of France. Response to sun compass cues was demonstrated in each population at the collection site and for the French population after transportation to Italy, where experiments were carried out on a differently oriented beach. Landscape cues were shown to improve the beetle's orientation capacity when these were tested together with a visible sun. Artificial landscapes were also tested under laboratory conditions. Different-sized silhouettes were placed in the four cardinal directions, and these envoked different responses depending on their height. The beetles oriented towards a black silhouette when this subtended an angle of 25°. The results obtained for the two populations are compared and discussed from an eco-ethological point of view. [ABSTRACT FROM AUTHOR]

Talitrus saltator biology, population dynamics, and reproduction were studied more or less simultaneously at three sand beaches: Lavos, on the western coast of Portugal; Collelungo, on the Italian coast of the Thyrrenian Sea; and Zouara, on the northern coast of Tunisia. The species exhibited a consistent pattern of aggregated distribution. Densities were higher at Lavos than at Collelungo and Zouara. Reproduction took place from early March to late September at Lavos and Collelungo, and from late February to early November at Zouara. The average sex ratio was favourable to males at Lavos and Collelungo, and to females at Zouara. Based on data from Lavos, the population abundance was positively correlated with temperature, while the percentage of juveniles in the population was positively correlated with temperature and sediment moisture. Adult individuals from the Atlantic population were larger than the Mediterranean ones, while newborn individuals from the Mediterranean were slightly larger than Atlantic ones. Life span was estimated at 7–11 months at Lavos, 6–9 months at Collelungo, and 6–8 months at Zouara. Cohorts born at the beginning of the reproductive period tend to have shorter lives than the ones born later in the season, with longer life spans occurring in cohorts that crossed the winter to breed in the next year. The minimum period necessary for sexual differentiation after birth was estimated at ±4 weeks at Lavos, ±3 weeks at Collelungo, and ±4.5 weeks at Zouara, for males, and ±6 weeks at Lavos, and ±5 weeks at Collelungo and Zouara, for females. The period necessary for female's sexual maturation after being born was estimated at ±10 weeks at Lavos, and ±8 weeks at Collelungo and Zouara. At the studied sites, T. saltator appeared as semiannual species, with iteroparous females appearing to produce at least two broods per year, and exhibited a bivoltine life cycle. Growth production (P) was estimated at 0.74 g m−2 yr−1 ash-free dry weight (AFDW; 17.7 kJ m−2 yr−1) at Lavos, 0.12 g m−2 yr−1 AFDW (2.8 kJ m−2 yr−1) at Collelungo, and 0.61 g m−2 yr−1 AFDW (14.3 kJ m−2 yr−1) at Zouara. Elimination production (E) was estimated at 1.40 g m−2 yr−1 AFDW (33.5 kJ m−2 yr−1) at Lavos, 0.20 g m−2 yr−1 AFDW (4.8 kJ m−2 yr−1) at Collelungo, and 1.11 g m−2 yr−1 AFDW (26.6 kJ m−2 yr−1) at Zouara. The average annual biomass (B¯) (standing stock) was estimated at 0.13 g m−2 at Lavos, 0.014 g m−2 at Collelungo, and 0.084 g m−2 at Zouara, resulting in P/B¯ ratios of 5.7 at Lavos, 8.2 at Collelungo, and 7.3 at Zouara, and E/B¯ ratios of 10.8 at Lavos, 14.4 at Collelungo, and 13.1 at Zouara. The present results, combined with information from literature, revealed a geographic variation in T. saltator populations with regard to their morphological characteristics, growth rates, life spans, and life cycles. [Copyright &y& Elsevier]