SYNCHRONIZATION TO LIGHT AND RESTRICTED-FEEDING SCHEDULES OF BEHAVIORAL AND HUMORAL DAILY RHYTHMS IN GILTHEAD SEA BREAM (SPARUS AURATA)

Abstract

Food is not continuously available in the wild, and so most animals show a wide variety of circadian rhythms that can be entrained to feeding time. The aim of this research was to evaluate the effect of time-restricted feeding on the daily rhythms of gilthead sea bream, with food being provided during the day or night under a 12:12 h light-dark (LD) cycle or constant light (LL) conditions. Self-feeding and locomotor activity, as well as daily rhythms of cortisol, glucose, and melatonin, were evaluated. Fish synchronized their feeding behavior to the feeding phase, so that in LD they displayed 78% nocturnal feeding activity under night-feeding and 81% diurnal feeding activity under day-feeding, while under LL-feeding they displayed 72% of their daily activity during the 12 h feeding phase. In contrast, locomotor activity was mostly diurnal (66–71%), regardless of the feeding schedule, and it became arrhythmic under LL. Cortisol showed daily rhythms that peaked at different times, depending on the light and feeding schedule: one peak several hours before feeding under day-feeding and night-feeding, and two peaks under LL-feeding. Glucose displayed low-amplitude variations, with no daily rhythms being detected. Melatonin, however, showed a nocturnal rhythm, regardless of the feeding schedule, while the rhythm became attenuated under LL. Taken together, these results highlight the role of feeding on endocrine and metabolic rhythms, suggesting that feeding behavior should be considered when studying these variables. (Author correspondence: [email protected])

Key Words:

• Teleost
• Feeding behavior
• Cortisol
• Glucose
• Melatonin

ACKNOWLEDGMENTS

This research was supported by the Spanish Ministry of Education and Science (MEC) by projects AGL2004-07984-C02-01 and AGL2007-66507-C02-02, granted to FJSV. The authors wish to thank the personnel of the Service of Support to the Experimental Sciences (SACE) of the University of Murcia for their help with sample preparation and analyses.