title: The skylight gradient of luminance helps sandhoppers in sun and moon identification.
abstract: To return to the ecologically optimal zone of the beach, the sandhopper Talitrus saltator (Montagu) maintains a constant sea-land direction based on the sun and moon compasses. In this study, we investigated the role of the skylight gradient of luminance in sun and moon identification under natural and artificial conditions of illumination. Clock-shifted (inverted) sandhoppers tested under the sun (during their subjective night) and under the full moon (during their subjective day) exhibit orientation in accordance with correct identification of the sun and the moon at night. Tested in artificial conditions of illumination at night without the artificial gradient of luminance, the artificial astronomical cue is identified as the moon even when the conditions of illumination allow sun compass orientation during the day. When the artificial gradient of luminance is added, the artificial astronomical cue is identified as the sun. The role of the sky gradient of luminance in sun and moon identification is discussed on the basis of present and past findings.
authors: Dipartimento Di Biologia Evoluzionistica, Università di Firenze, Via Romana 17, 50125 Firenze, Italy. alberto.ugolini@unifi.it
authors: Alberto
authors: A
authors: Ugolini
authors: Giuditta
authors: G
authors: Galanti
authors: Luca
authors: L
authors: Mercatelli
mesh_terms: D033304:Amphipoda / Q000502:physiology*; D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D016081:Moon; D012623:Seawater; D013472:Sunlight