title: Melatonin: a possible link between the presence of artificial light at night and reductions in biological fitness.
abstract: The mechanisms underpinning the ecological impacts of the presence of artificial night lighting remain elusive. One suspected underlying cause is that the presence of light at night (LAN) supresses nocturnal production of melatonin, a key driver of biological rhythm and a potent antioxidant with a proposed role in immune function. Here, we briefly review the evidence for melatonin as the link between LAN and changes in behaviour and physiology. We then present preliminary data supporting the potential for melatonin to act as a recovery agent mitigating the negative effects of LAN in an invertebrate. Adult crickets (Teleogryllus commodus), exposed to constant illumination, were provided with dietary melatonin (concentrations: 0, 10 or 100 µg ml(-1)) in their drinking water. We then compared survival, lifetime fecundity and, over a 4-week period, immune function (haemocyte concentration, lysozyme-like and phenoloxidase (PO) activity). Melatonin supplementation was able only partially to mitigate the detrimental effects of LAN: it did not improve survival or fecundity or PO activity, but it had a largely dose-dependent positive effect on haemocyte concentration and lysozyme-like activity. We discuss the implications of these relationships, as well as the usefulness of invertebrates as model species for future studies that explore the effects of LAN.
authors.affiliation: Department of Zoology, The University of Melbourne, 3010 VIC, Australia theresa@unimelb.edu.au.
authors.forename: Therésa M
authors.initials: TM
authors.lastname: Jones
authors.affiliation: Department of Zoology, The University of Melbourne, 3010 VIC, Australia.
authors.forename: Joanna
authors.initials: J
authors.lastname: Durrant
authors.affiliation: Department of Zoology, The University of Melbourne, 3010 VIC, Australia.
authors.forename: Ellie B
authors.initials: EB
authors.lastname: Michaelides
authors.affiliation: Department of Zoology, The University of Melbourne, 3010 VIC, Australia.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Green
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D056084:Genetic Fitness; D006135:Gryllidae / Q000528:radiation effects*; D008029:Lighting / Q000009:adverse effects*; D008136:Longevity / Q000528:radiation effects*; D008550:Melatonin / Q000494:pharmacology*; D018384:Oxidative Stress; D012098:Reproduction / Q000187:drug effects / Q000528:radiation effects
chemical_list: D008550:Melatonin
keywords: immunomodulation; invertebrates; light at night; melatonin