Variation in zonal recovery in four Talitrus saltator populations from different coastlines: a comparison of orientation in the field and in an experimental arena

Variation of genetic and behavioural traits in the sandhopperTalitrus saltator(Crustacea Amphipoda) along a dynamic sand beach

“…This activity has a circadian rhythm (NARDI et al 2003). When the sand dries up for increasing insulation, and/or animals are removed from the substratum during the day, they regain the wet zone seawards BORGIOLI et al 1999). The expected orientation seawards is called the theoretical escape direction (TED); it is assumed to be perpendicular to the coastline and changes according to the orientation of the shoreline.…”

Seasonal variation in the orientation ofTalitrus saltatoron a Mediterranean sandy beach: an ecological interpretation

“…This different behaviour is adaptive, as on Mediterranean coasts the high risk of dehydration in summer makes a correct zonal recovery essential for the sandhoppers' survival, while the mild autumnal climate permits a certain degree of dispersion on the supralittoral zone also during the day hours. Such a dependence on seasonal climatic variations was already described for a variety of Mediterranean locations and behaviours of T. saltator (BORGIOLI et al 1999a(BORGIOLI et al , 1999bNARDI et al 2003;FANINI et al 2007). On the other hand, it was found that on beaches with more marked tidal excursions, the sandhoppers are more influenced by tides (linked to the submersion risk; BORGIOLI et al 1999b;GAMBINERI et al 2008;ROSSANO et al 2009;BESSA et al 2013).…”

“…Such a redundancy of mechanisms was observed also for other crustaceans (ALTIZER & FORWARD 1993;CAMERON & FORWARD 1993;CHIUSSI & DÍAZ 2001), insects and spiders (COLLETT & COLLETT 2000;MORSE 2002;BISCH-KNADEN & WEHNER 2003;NØRGAARD et al 2007). The ecological and morphological features of beaches are known to influence the behaviour of T. saltator, such as the rate of exposure to waves and tidal range (MEZZETTI et al 1994;WILLIAMS 1995), wrack abundance and distribution (BORGIOLI et al 1999b;NARDI et al 2003), the degree of stability of the shoreline (SCAPINI et al 1995;BORGIOLI et al 1999a;ELGTARI et al 2000) and the seasonal climatic variations (WILLIAMS 1995;NARDI et al 2003). According to these studies, talitrids express a high behavioural plasticity to survive on sandy beaches; natural selection may have determined the best direction for the solar orientation of each population, but it also may have maintained individual flexibility in the use of learned references and behaviour modulation, permitting sandhoppers to face periodic, life-long or sudden risks and shoreline variations (BROWN 1996;MCLACHLAN & BROWN 2006).…”

Sandhopper orientation under natural conditions: Comparing individual tracks

“…Theoretically, when individuals are displaced in the upper beach, they orient to the theoretical escape direction seawards (TED) following a trajectory nearly perpendicular to the shoreline (Pardi and Papi, 1953). The sun compass was shown to be genetically fixed in those populations where the shoreline had not changed in the long term (centuries), while on highly dynamic, eroded or accreting shorelines (changing in the medium term of years or decades) sandhoppers tend to scatter in various directions, or to orient on the basis of local landscape features Borgioli et al, 1999b;D'Elia et al, 2001). Scattering can depend on genetic variation or behavioral flexibility.…”