Feeding time synchronises daily rhythms of behaviour and digestive physiology in gilthead seabream (Sparus aurata)

Feeding cycles entrain biological rhythms, which enables animals to anticipate feeding times and so maximizes food utilization. In this article the effect of mealtime on locomotor activity, blood glucose, gastric pH and digestive enzymes was studied in two groups of seabream (Sparus aurata): one group received a single daily meal at random times either during the light or the dark (random feeding, RF), whereas the other group received the meal during the light period every day at the same time (periodic feeding, PF). PF fish showed strong synchronisation of locomotor activity to the light phase (97.9 ± 0.2% of their total daily activity during daytime). In addition, the locomotor activity rhythm of PF fish showed a statistically significant daily rhythm (p < 0.05) for a period of 24 h, whereas RF fish did not display a statistically significant rhythm. Blood glucose levels were higher in RF fish during the 8 h following feeding. Gastric pH showed a postprandial decrease in both groups, but RF fish showed a lower daily average value (4.31 ± 0.21 compared with 5.52 ± 0.20). Amylase and alkaline protease activity increased some hours before mealtime in PF fish, whereas amylase activity increased 1 h after feeding and alkaline protease showed no statistically significant differences in RF fish. Acid protease activity showed no statistically significant differences in any group. Taken together, these results demonstrate that altering the feeding time affects the physiology and behaviour of seabream, which have the capacity to prepare themselves for a forthcoming meal.