Bivalve mollusc circadian clock genes can run at tidal frequency

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: TRAN, Damien, PERRIGAULT, Mickael, CIRET, Pierre, PAYTON, Laura
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Circatidal clock; circadian clock; tidal rhythm; biological timing; oyster; bimodal behavior; Sciences de l'environnement; Sciences du Vivant [q-bio]; Crassostrea gigas
• Online Access: https://oskar-bordeaux.fr/handle/20.500.12278/189137; https://hdl.handle.net/20.500.12278/189137; https://doi.org/10.1098/rspb.2019.2440

Marine coastal habitats are complex cyclic environments as a result of sun and moon interactions. In contrast to the well-known circadian orchestration of the terrestrial animal rhythmicity (~24h), the mechanism responsible for the circatidal rhythm (~12.4h) remains largely elusive in marine organisms. We revealed in subtidal field conditions that the oyster Crassostrea gigas exhibits tidal rhythmicity of circadian clock genes and clock-associated genes. Free-running experiment showed an endogenous circatidal rhythm. In parallel, we showed in the field that oysters’ valve behavior exhibited a strong tidal rhythm combined with a daily rhythm. In the free-running experiment, all behavioral rhythms were circatidal, and half of them were also circadian. Our results fuel the debate on endogenous circatidal mechanisms. In contrast to the current hypothesis on the existence of an independent tidal clock, we suggest that a single “circadian/circatidal” clock in bivalves is sufficient to entrain behavioral patterns at tidal and daily frequencies.