title: Field chronobiology of a molluscan bivalve: how the moon and sun cycles interact to drive oyster activity rhythms.
abstract: The present study reports new insights into the complexity of environmental drivers in aquatic animals. The focus of this study was to determine the main forces that drive mollusc bivalve behavior in situ. To answer this question, the authors continuously studied the valve movements of permanently immersed oysters, Crassostrea gigas, during a 1-year-long in situ study. Valve behavior was monitored with a specially build valvometer, which allows continuously recording of up to 16 bivalves at high frequency (10 Hz). The results highlight a strong relationship between the rhythms of valve behavior and the complex association of the sun-earth-moon orbital positions. Permanently immersed C. gigas follows a robust and strong behavior primarily driven by the tidal cycle. The intensity of this tidal driving force is modulated by the neap-spring tides (i.e., synodic moon cycle), which themselves depend of the earth-moon distance (i.e., anomalistic moon cycle). Light is a significant driver of the oysters' biological rhythm, although its power is limited by the tides, which remain the predominant driver. More globally, depending where in the world the bivalves reside, the results suggest their biological rhythms should vary according to the relative importance of the solar cycle and different lunar cycles associated with tide generation. These results highlight the high plasticity of these oysters to adapt to their changing environment.
authors.affiliation: UMR 5805 EPOC, University Bordeaux 1 and CNRS, Arcachon, France. d.tran@epoc.ubordeaux1.fr
authors.forename: Damien
authors.initials: D
authors.lastname: Tran
authors.forename: Arnaud
authors.initials: A
authors.lastname: Nadau
authors.forename: Gilles
authors.initials: G
authors.lastname: Durrieu
authors.forename: Pierre
authors.initials: P
authors.lastname: Ciret
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Parisot
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Massabuau
mesh_terms: D000204:Activity Cycles / Q000502:physiology; D000818:Animals; D002909:Chronobiology Phenomena; D002940:Circadian Rhythm / Q000502:physiology; D049896:Crassostrea / Q000254:growth & development / Q000502:physiology*; D017753:Ecosystem; D008954:Models, Biological; D016081:Moon; D010507:Periodicity; D016082:Solar System