Photic entrainment of daily rhythm pattern of locomotor activity in sea bass (Dicentrarcus labrax)

Abstract

The aim of this study was to evaluate the circadian rhythm of daily locomotor activity in sea bass exposed to three different artificial lighting regimes including 12/12, 24/0, and 0/24 L/D periods, and scheduled daytime feeding. Daily rhythm of locomotor activity during 12/12 L/D was observed, whereas locomotor activity recorded during 24/0 and 0/24 L/D resulted arrhythmic. Statistical differences in mesor values among the photoperiods and between light and dark phases of each photoperiod were found. During the 12/12 and 0/24 L/D, the fish were active mostly during the light phase. During 24/0 L/D, a phase inversion occurred. The results showed that photoperiod is a dominant synchronizer in sea bass, and that the appetite in this fish follows daily rhythms which does not match the imposed feeding schedule, suggesting the absence or the lability of internal process that couples feeding cycles and biological rhythms.

Keywords:

• Dicentrarcus labrax
• locomotor activity
• photoperiod
• biological rhythm
• feeding schedule

Acknowledgement

This study was partially supported by PON02 00451 3362185 INNOVAQUA – Innovazione Tecnologica a Supporto dell’Incremento della Produttività e della Competitività dell’Acquacoltura Siciliana.

Disclosure statement

No potential conflict of interest was reported by the authors.