The sun compass of the sandhopper Talitrus saltator: the speed of the chronometric mechanism depends on the hours of light.
Experiments on solar orientation were conducted with adult amphipods (Talitrus saltator) subjected to a reduction and/or phase shift of the hours of light (L) or dark (D) with respect to the natural photoperiod: 15 h:9 h L:D (controls), 15 h:9 h inverted (i.e. phase-shifted by 12 h and tested with the sun during the subjective night), 4 h:20 h, 20 h:4 h inverted. The sandhoppers were released in a confined environment, and individual orientation angles were recorded. The results confirm the continuous operation, through the entire 24-h period, of a chronometric mechanism of compensation for apparent solar motion. They show excellent agreement with a recently proposed model of compensation for the sun at constant (not differential) speed and they demonstrate a dependence of the speed of the chronometric mechanism on the L:D ratio in the 24-h period.
Ugolini
Alberto
A
Dipartimento di Biologia Animale e Genetica, Università di Firenze, Via Romana 17, Italy. ugolini_alb@dbag.unifi.it
Tiribilli
Bruno
B
Boddi
Vieri
V
D033304:Amphipoda / Q000502:physiology*; D002909:Chronobiology Phenomena; D008027:Light; D017440:Photoperiod; D012044:Regression Analysis; D016082:Solar System; D013028:Space Perception; D013997:Time Factors