Effect of experience on the reaction of sandhoppers to wet and dry substrates and monochromatic lights

The aim of this paper is the study of the inherited directional tendency in sandhoppers and its reaction norm, analyzing two of its components, the reaction to releasing stimuli and the phototactic response. Young experienced (wild) and inexperienced (laboratory-born) specimens of Talitrus saltator (Montagu 1808) were tested singly and repeatedly in a test arena under the sun on dry and wet substrates, and in the laboratory with monochromatic artificial lights (blue and yellow-green). The directional tendency towards the home-sea of laboratoryborn individuals in response to a dry substrate improved with successive trials while wild sandhoppers responded promptly and were more concentrated seawards. On the other hand, the innate directional tendency towards land on a wet substrate, demonstrated here for the first time in Mediterranean talitrids, did not change with experience. Tested with monochromatic lights, the laborat o y b o r n individuals reacted in the main photopositively, but tended to change their reactions after the first trial; wild individuals showed a stronger reaction to the light and, in some cases, tended to orient photomenotactically. The reaction of both laboratory-born and wild sandhoppers was stronger in respect to blue than to yellow-green light.