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The Journal of Experimental Biology 205, 3225-3230 (2002)
Copyright © 2002 The Company of Biologists Limited

The sun compass of the sandhopper Talitrus saltator: the speed of the chronometric mechanism depends on the hours of light

Alberto Ugolini1,*, Bruno Tiribilli2 and Vieri Boddi3

1 Dipartimento di Biologia Animale e Genetica, Università di Firenze, Via Romana 17, 50125 Firenze, Italy
2 Istituto Nazionale di Ottica Applicata, Firenze, Italy
3 Dipartimento di Sanità Pubblica, Università di Firenze, Italy

* Author for correspondence (e-mail: ugolini_alb{at}dbag.unifi.it)

Accepted 8 July 2002

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.

Key words: orientation, sun compass, chronometric mechanism, sandhopper, Talitrus saltator






© The Company of Biologists Ltd 2002