ARTIFICIAL-LIGHT AND SUN COMPASS ORIENTATION IN THE SANDHOPPER TALITRUS SALTATOR (CRUSTACEA, AMPHIPODA)

Experiments on compass orientation under artificial light were conduct ed with adult individuals of Talitrus saltator. The aim was to reprodu ce in the laboratory an orientation based on the sun compass correspon ding to that recorded in conditions of the true sun and sky. This was obtained by the creation within an opaque Plexiglas dome of a scenario that permitted variation of the brightness of the artificial sky and sun. The results show that it is possible to obtain sun compass orient ation corresponding to the natural situation even in an artificial env ironment. It can be concluded that sandhoppers identify an artificial light source as the sun if the artificial sky is also illuminated and if the intensities of the artificial sun and sky exceed certain thresh old values (1.13 and 10 mu W cm(-2), respectively). The results of oth er experiments under the natural blue sky with an artificial sun and w ith the real sun attenuated are discussed.