Phase-shifting the light-dark cycle influences food-anticipatory activity in golden shiners

This study provides evidence that a circadian light-entrainable oscillator is at least partially involved in the timing of food-anticipatory activity (FAA) in a fish, the golden shiner, Notemigonus crysoleucas. Shoals of four golden shiners were fed for 11-20 days at a fixed daily time (either early night, midnight, late night, early day, midday, or late day). Most (78%) s hoals developed peaks of FAA during that period of time. Food was then with held for 7 days, and the light-dark (LD) cycle was either advanced or delay ed by 6 h on the first of those days. The activity waveform of most (53-58% ) shoals shifted along with the LD cycle, as indicated by significant corre lation coefficients between pre- and postshift waveforms plotted relative t o LD. Nonsignificant correlations were linked to low activity levels rather than to persistence of the activity peak at the old clock time. Activity s hifts were gradual, taking 2-4 days, which indicates that the underlying me chanism is circadian rather than hourglass. (C) 2000 Elsevier Science Inc. All rights reserved.