Daily rhythms of clock gene expression and feeding behavior during the larval development in gilthead seabream,Sparus aurata

Alterations in photoperiod significantly affect the expression of clock genes in gilthead seabream larvae.

• Under a regular light-dark cycle (12L:12D), larvae exhibited synchronized feeding and clock gene expression patterns.
• In continuous light (24L:0D), larvae maintained rhythmic patterns, but the timing of peaks varied with age.
• At 60 days post-hatch, clock gene expression and feeding rhythms in continuous light were similar to those in the light-dark cycle.
• The expression levels of the genes bmal1 and cry1 were considerably lower in continuous light compared to the light-dark cycle.
• The two-phases photoperiod (LL + LD) indicated age-dependent responses, with younger larvae resembling continuous light patterns and older ones resembling light-dark patterns.
• These findings suggest that internal mechanisms influence rhythmic physiological responses in developing fish larvae under varying light conditions.

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