Green land and blue sea: a coloured landscape in the orientation of the sandhopper Talitrus saltator (Montagu) (Amphipoda, Talitridae).

The use of the landscape in the zonal recovery of Talitrus saltator (Montagu) was demonstrated in the past using natural and artificial landscapes. Here we evaluate the importance of colour in the landscape orientation of sandhoppers. Adult individuals of T. saltator were released in a Plexiglas bowl under the sun, with a view of an artificial landscape: a black cardboard strip or a pair of differently coloured filters, each occupying 180 degrees of the horizon. Our results not only confirm the influence of the black and white artificial landscape-based compass cue on the zonal orientation of T. saltator, but also show that vision of a blue and green artificial landscape affects the direction of orientation; in fact, the orientation agreed with the directional indication of the landscape even when it contrasted with the sun compass indication. The same result was obtained with a blue-grey and green-grey landscape, but not with pairs of grey filters. Therefore, in the sandhoppers' visual world, a coloured landscape that matches the prevalent natural field colours greatly contributes to their directional choice.