Orientation and migration in Talitrus saltator

Talitrus saltator, a beach dwelling crustacean amphipod, has been for long the subject of orientation studies, as it shows orientation perpendicular to the shoreline in response to stressful factors of environmental dryness or submersion. Sun orientation permits zonal recovery in case of abrupt displacement from their burrows during the day, and is inherited with genetic differences among populations from differently oriented shores. Other orientation mechanisms are used in addition to or instead of the sun compass to maintain zonation. A learning capability has also been shown. which can modify the orientation after individual experience. Rhythmic components in the orientational responses have been demonstrated, which would be related to daily migrations in nature. In the laboratory under constant conditions. Sandhoppers show rhythmic changes in their responses to simple v'isual stimuli and differences have been shown among populations from Mediterranean and Atlantic shores. A study is here presented aimed at answering the still open question of whether and how sandhoppers are oriented in nature during the foraging movements, which they perform at night under suitable meteorological conditions. Spontaneously active sandhoppers were captured with pit-fall cross traps positioned on the eulittoral and shortly after tested in orientation arenas. Changes in sandhopper orientation resulted during the night, which were related to their zonation and activity. The orientational cues were visual, to both sky and landscape factors. On the whole, the results throw new light on the ecological meaning of sandhoppers orientation and the conditions in which learning of direction finding may occur in nature.