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

TY - JOUR

T1 - Melatonin and corticosterone profiles under polar day in a seabird with sexually-opposite activity-rhythms

AU - Per Huffeldt, Nicholas

AU - Merkel, Flemming R

AU - Jenni-Eiermann, Susanne

AU - Goymann, Wolfgang

AU - Helm, Barbara

N1 - Copyright © 2019 Elsevier Inc. All rights reserved.

PY - 2020/1/1

Y1 - 2020/1/1

N2 - 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.

AB - 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.

KW - Activity rhythm

KW - Circadian rhythm

KW - Corticosterone

KW - Melatonin

KW - Polar day

KW - Uria lomvia

U2 - 10.1016/j.ygcen.2019.113296

DO - 10.1016/j.ygcen.2019.113296

M3 - Journal article

C2 - 31589833

SN - 0016-6480

VL - 285

JO - General and Comparative Endocrinology

JF - General and Comparative Endocrinology

M1 - 113296

ER -