Melatonin and corticosterone profiles under polar day in a seabird with sexually-opposite activity-rhythms

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  • Nicholas Per Huffeldt, Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA. Electronic address: nph@bios.au.dk.
  • ,
  • Flemming R Merkel
  • Susanne Jenni-Eiermann, Swiss Ornithological Institute, CH-6204 Sempach, Switzerland.
  • ,
  • Wolfgang Goymann, Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, D-82319 Seewiesen, Germany.
  • ,
  • Barbara Helm, IBAHCM, University of Glasgow, Glasgow G12 8QQ, United Kingdom; Groningen Institute for Evolutionary Life Sciences (GELIFES), University of Groningen, 9747 AG Groningen, Netherlands.

The 24 h geophysical light-dark cycle is the main organizer of daily rhythms, scheduling physiology and behavior. This cycle attenuates greatly during the continuous light of summer at polar latitudes, resulting in species-specific and even individual-specific patterns of behavioral rhythmicity, but the physiological mechanisms underlying this variation are poorly understood. To address this knowledge gap and to better understand the roles of the hormones melatonin and corticosterone in rhythmic behavior during polar day, we exploited the behavior of thick-billed murres (Uria lomvia), a charadriiform seabird with sexually opposite ('antiphase') activity-rhythms on a 24 h cycle during the continuous light of polar summer. Melatonin concentration in the plasma of inactive males was unexpectedly high around midday and subsequently fell during a sudden decrease in light intensity as the colony became shaded. Corticosterone concentration in plasma did not vary with time of day or activity in either sex. While the reasons for these unusual patterns remain unclear, we propose that a flexible melatonin response and little diel variation of corticosterone may be adaptive in thick-billed murres, and perhaps other polar birds and mammals, by stabilizing glucocorticoids' role of modulating energy storage and mobilization across the diel cycle and facilitating the appropriate reaction to unexpected stimuli experienced across the diel cycle while attending the colony.

Original languageEnglish
Article number113296
JournalGeneral and Comparative Endocrinology
Volume285
Number of pages8
ISSN0016-6480
DOIs
Publication statusPublished - 1 Jan 2020

Bibliographical note

Copyright © 2019 Elsevier Inc. All rights reserved.

    Research areas

  • Activity rhythm, Circadian rhythm, Corticosterone, Melatonin, Polar day, Uria lomvia

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