title: Dopamine is a key regulator in the signalling pathway underlying predator-induced defences in Daphnia.
abstract: The waterflea Daphnia is a model to investigate the genetic basis of phenotypic plasticity resulting from one differentially expressed genome. Daphnia develops adaptive phenotypes (e.g. morphological defences) thwarting predators, based on chemical predator cue perception. To understand the genomic basis of phenotypic plasticity, the description of the precedent cellular and neuronal mechanisms is fundamental. However, key regulators remain unknown. All neuronal and endocrine stimulants were able to modulate but not induce defences, indicating a pathway of interlinked steps. A candidate able to link neuronal with endocrine responses is the multi-functional amine dopamine. We here tested its involvement in trait formation in Daphnia pulex and Daphnia longicephala using an induction assay composed of predator cues combined with dopaminergic and cholinergic stimulants. The mere application of both stimulants was sufficient to induce morphological defences. We determined dopamine localization in cells found in close association with the defensive trait. These cells serve as centres controlling divergent morphologies. As a mitogen and sclerotization agent, we anticipate that dopamine is involved in proliferation and structural formation of morphological defences. Furthermore, dopamine pathways appear to be interconnected with endocrine pathways, and control juvenile hormone and ecdysone levels. In conclusion, dopamine is suggested as a key regulator of phenotypic plasticity.
authors.affiliation: Department of Animal Ecology, Evolution and Biodiversity, Ruhr University Bochum, Universitätsstrasse 150, Bochum 44801, Germany Environmental Genomics Group, School of Biosciences, University of Birmingham, Birmingham B18 2TT, UK linda.weiss@rub.de.
authors.forename: Linda C
authors.identifier: http://orcid.org/0000-0002-7737-5017
authors.initials: LC
authors.lastname: Weiss
authors.affiliation: Department of Animal Ecology, Evolution and Biodiversity, Ruhr University Bochum, Universitätsstrasse 150, Bochum 44801, Germany Aquatic Ecosystem Research Group, University of Duisburg and Essen, Universitätsstrasse 5, Essen 45141, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Leese
authors.affiliation: Aquatic Ecosystem Research Group, University of Duisburg and Essen, Universitätsstrasse 5, Essen 45141, Germany Department of Animal Ecology I, University Bayreuth, Universitätsstrasse 30, Bayreuth 95447, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Laforsch
authors.affiliation: Department of Animal Ecology, Evolution and Biodiversity, Ruhr University Bochum, Universitätsstrasse 150, Bochum 44801, Germany.
authors.forename: Ralph
authors.initials: R
authors.lastname: Tollrian
mesh_terms: D000818:Animals; D003621:Daphnia / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism*; D020387:Food Chain; D010641:Phenotype; D011235:Predatory Behavior; D015398:Signal Transduction; D013045:Species Specificity
chemical_list: D004298:Dopamine
keywords: Daphnia; dopamine; inducible defences; neurophysiology; phenotypic plasticity; polyploid cells