title: Synchronization to light and mealtime of daily rhythms of locomotor activity, plasma glucose and digestive enzymes in the Nile tilapia (Oreochromis niloticus).
abstract: The light-dark cycle and feeding can be the most important factors acting as synchronizers of biological rhythms. In this research we aimed to evaluate synchronization to feeding schedule of daily rhythms of locomotor activity and digestive enzymes of tilapia. For that purpose, 120 tilapias (65.0±0.6g) were distributed in 12 tanks (10 fish per tank) and divided into two groups. One group was fed once a day at 11:00h (zeitgeber time, ZT6) (ML group) and the other group was fed at 23:00h (ZT18) (MD group). The fish were anesthetized to collect samples of blood, stomach and midgut at 4-hour intervals over a period of 24h. Fish fed at ML showed a diurnal locomotor activity (74% of the total daily activity occurring during the light phase) and synchronization to the feeding schedule, as this group showed anticipation to the feeding time. Fish fed at MD showed a disruption in the pattern of locomotor activity and became less diurnal (59%). Alkaline protease activity in the midgut showed daily rhythm with the achrophase at the beginning of the dark phase in both ML and MD groups. Acid protease and amylase did not show significant daily rhythms. Plasma glucose showed a daily rhythm with the achrophase shifted by 12h in the ML and MD groups. These results revealed that the feeding time and light cycle synchronize differently the daily rhythms of behavior, digestive physiology and plasma metabolites in the Nile tilapia, which indicate the plasticity of the circadian system and its synchronizers.
authors.affiliation: Department of Animal Science and Veterinary Medicine, Campus Salvador, Federal University of Bahia (UFBA), 40170-110, Bahia, Brazil.
authors.forename: Bartira
authors.initials: B
authors.lastname: Guerra-Santos
authors.affiliation: Department of Physiology, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, 30100 Murcia, Spain.
authors.forename: José Fernando
authors.initials: JF
authors.lastname: López-Olmeda
authors.affiliation: Department of Animal Science and Veterinary Medicine, Campus Salvador, Federal University of Bahia (UFBA), 40170-110, Bahia, Brazil.
authors.forename: Bruno Olivetti
authors.initials: BO
authors.lastname: de Mattos
authors.affiliation: Laboratory of Fish Nutrition and Feeding Behaviour (AquaUFRB), Faculty of Fishing Engineering (NEPA), Center of Agricultural Science, Environmental and Biological (CCAAB), University of Bahia (UFRB), 44380-000 Cruz das Almas, Brazil.
authors.forename: Alice Borba
authors.initials: AB
authors.lastname: Baião
authors.affiliation: Laboratory of Fish Nutrition and Feeding Behaviour (AquaUFRB), Faculty of Fishing Engineering (NEPA), Center of Agricultural Science, Environmental and Biological (CCAAB), University of Bahia (UFRB), 44380-000 Cruz das Almas, Brazil.
authors.forename: Denise Soledade Peixoto
authors.initials: DSP
authors.lastname: Pereira
authors.affiliation: Department of Physiology, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, 30100 Murcia, Spain.
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Sánchez-Vázquez
authors.affiliation: Laboratory of Fish Nutrition and Feeding Behaviour (AquaUFRB), Faculty of Fishing Engineering (NEPA), Center of Agricultural Science, Environmental and Biological (CCAAB), University of Bahia (UFRB), 44380-000 Cruz das Almas, Brazil.
authors.forename: Robson Bahia
authors.initials: RB
authors.lastname: Cerqueira
authors.affiliation: Department of Animal Science and Veterinary Medicine, Campus Salvador, Federal University of Bahia (UFBA), 40170-110, Bahia, Brazil.
authors.forename: Ricardo Castelo Branco
authors.initials: RCB
authors.lastname: Albinati
authors.affiliation: Laboratory of Fish Nutrition and Feeding Behaviour (AquaUFRB), Faculty of Fishing Engineering (NEPA), Center of Agricultural Science, Environmental and Biological (CCAAB), University of Bahia (UFRB), 44380-000 Cruz das Almas, Brazil. Electronic address: fortes@ufrb.edu.br.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Fortes-Silva
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000681:Amylases / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D004064:Digestive System / Q000201:enzymology; D005247:Feeding Behavior / Q000502:physiology*; D008027:Light; D008124:Locomotion / Q000502:physiology*; D017210:Tilapia / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D000681:Amylases
keywords: Amylase; Feeding time; Glucose rhythms; Nile tilapia; Protease rhythms