title: Melatonin signaling controls circadian swimming behavior in marine zooplankton.
abstract: Melatonin, the "hormone of darkness," is a key regulator of vertebrate circadian physiology and behavior. Despite its ubiquitous presence in Metazoa, the function of melatonin signaling outside vertebrates is poorly understood. Here, we investigate the effect of melatonin signaling on circadian swimming behavior in a zooplankton model, the marine annelid Platynereis dumerilii. We find that melatonin is produced in brain photoreceptors with a vertebrate-type opsin-based phototransduction cascade and a light-entrained clock. Melatonin released at night induces rhythmic burst firing of cholinergic neurons that innervate locomotor-ciliated cells. This establishes a nocturnal behavioral state by modulating the length and the frequency of ciliary arrests. Based on our findings, we propose that melatonin signaling plays a role in the circadian control of ciliary swimming to adjust the vertical position of zooplankton in response to ambient light.
authors.affiliation: European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany. Electronic address: tosches@embl.de.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Tosches
authors.affiliation: European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany; Centre for Organismal Studies (COS), University of Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bucher
authors.affiliation: European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors.forename: Pavel
authors.initials: P
authors.lastname: Vopalensky
authors.affiliation: European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany; Centre for Organismal Studies (COS), University of Heidelberg, 69120 Heidelberg, Germany. Electronic address: arendt@embl.de.
authors.forename: Detlev
authors.initials: D
authors.lastname: Arendt
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002923:Cilia / Q000502:physiology; D057906:Circadian Clocks; D002940:Circadian Rhythm; D005786:Gene Expression Regulation; D007814:Larva / Q000378:metabolism; D008550:Melatonin / Q000378:metabolism*; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000378:metabolism*; D011077:Polychaeta / Q000166:cytology / Q000502:physiology*; D013550:Swimming; D015048:Zooplankton / Q000166:cytology / Q000502:physiology
chemical_list: D008550:Melatonin