Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination
Most organisms in temperate or tropic regions employ the light-dark (LD) cycle as the primary Zeitgeber to synchronize circadian rhythms. At higher latitudes (>66°33′), continuous illumination during the summer presents a significant time-keeping dilemma for polar-adapted species. Lapland lon...
Published in: | Journal of Biological Rhythms |
---|---|
Main Authors: | , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
SAGE Publications
2014
|
Subjects: | |
Online Access: | http://dx.doi.org/10.1177/0748730414552323 http://journals.sagepub.com/doi/pdf/10.1177/0748730414552323 http://journals.sagepub.com/doi/full-xml/10.1177/0748730414552323 |
id |
crsagepubl:10.1177/0748730414552323 |
---|---|
record_format |
openpolar |
spelling |
crsagepubl:10.1177/0748730414552323 2023-05-15T15:02:21+02:00 Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination Ashley, Noah T. Ubuka, Takayoshi Schwabl, Ingrid Goymann, Wolfgang Salli, Brady M. Bentley, George E. Buck, C. Loren 2014 http://dx.doi.org/10.1177/0748730414552323 http://journals.sagepub.com/doi/pdf/10.1177/0748730414552323 http://journals.sagepub.com/doi/full-xml/10.1177/0748730414552323 en eng SAGE Publications http://journals.sagepub.com/page/policies/text-and-data-mining-license Journal of Biological Rhythms volume 29, issue 6, page 456-469 ISSN 0748-7304 1552-4531 Physiology (medical) Physiology journal-article 2014 crsagepubl https://doi.org/10.1177/0748730414552323 2022-05-26T08:11:59Z Most organisms in temperate or tropic regions employ the light-dark (LD) cycle as the primary Zeitgeber to synchronize circadian rhythms. At higher latitudes (>66°33′), continuous illumination during the summer presents a significant time-keeping dilemma for polar-adapted species. Lapland longspurs ( Calcarius lapponicus), arctic-breeding migratory songbirds, are one of the few recorded species maintaining an intact diel rhythm in activity and plasma melatonin titers during polar summer. However, it is unknown whether rhythms are endogenous and entrain to low-amplitude polar Zeitgeber signals, such as daily variations in light intensity and the spectral composition of the sun (as measured by color temperature). Wild-caught male and female longspurs were brought into captivity, and locomotor activity was assessed using infrared detection. To examine if rhythms were endogenous, birds were exposed to constant bright light (LL; 1300 lux) or constant darkness (DD; 0.1 lux). All birds exhibited free-running activity rhythms in LL and DD, suggesting the presence of a functional circadian clock. Mean periods in LL (22.86 h) were significantly shorter than those in DD (23.5 h), in accordance with Aschoff’s rule. No birds entrained to diel changes in light intensity, color temperature, or both. To examine endogenous molecular clock function, the Per2 gene was partially cloned in longspurs (ll Per2) and transcripts were measured in hypothalamic tissue punches, eye, and liver using competitive polymerase chain reaction. Ocular ll Per2 gene expression was periodic in LL and elevated at ZT24 (CT24) for LD or constant conditions (LL and DD), but ll Per2 rhythmicity was not detected in hypothalamus or liver. Plasma melatonin was significantly lower in LL compared with LD or DD. In conclusion, rhythmic ocular Per2 expression and melatonin secretion may maintain the circadian activity rhythm across the polar day. Article in Journal/Newspaper Arctic Lapland SAGE Publications (via Crossref) Arctic Journal of Biological Rhythms 29 6 456 469 |
institution |
Open Polar |
collection |
SAGE Publications (via Crossref) |
op_collection_id |
crsagepubl |
language |
English |
topic |
Physiology (medical) Physiology |
spellingShingle |
Physiology (medical) Physiology Ashley, Noah T. Ubuka, Takayoshi Schwabl, Ingrid Goymann, Wolfgang Salli, Brady M. Bentley, George E. Buck, C. Loren Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination |
topic_facet |
Physiology (medical) Physiology |
description |
Most organisms in temperate or tropic regions employ the light-dark (LD) cycle as the primary Zeitgeber to synchronize circadian rhythms. At higher latitudes (>66°33′), continuous illumination during the summer presents a significant time-keeping dilemma for polar-adapted species. Lapland longspurs ( Calcarius lapponicus), arctic-breeding migratory songbirds, are one of the few recorded species maintaining an intact diel rhythm in activity and plasma melatonin titers during polar summer. However, it is unknown whether rhythms are endogenous and entrain to low-amplitude polar Zeitgeber signals, such as daily variations in light intensity and the spectral composition of the sun (as measured by color temperature). Wild-caught male and female longspurs were brought into captivity, and locomotor activity was assessed using infrared detection. To examine if rhythms were endogenous, birds were exposed to constant bright light (LL; 1300 lux) or constant darkness (DD; 0.1 lux). All birds exhibited free-running activity rhythms in LL and DD, suggesting the presence of a functional circadian clock. Mean periods in LL (22.86 h) were significantly shorter than those in DD (23.5 h), in accordance with Aschoff’s rule. No birds entrained to diel changes in light intensity, color temperature, or both. To examine endogenous molecular clock function, the Per2 gene was partially cloned in longspurs (ll Per2) and transcripts were measured in hypothalamic tissue punches, eye, and liver using competitive polymerase chain reaction. Ocular ll Per2 gene expression was periodic in LL and elevated at ZT24 (CT24) for LD or constant conditions (LL and DD), but ll Per2 rhythmicity was not detected in hypothalamus or liver. Plasma melatonin was significantly lower in LL compared with LD or DD. In conclusion, rhythmic ocular Per2 expression and melatonin secretion may maintain the circadian activity rhythm across the polar day. |
format |
Article in Journal/Newspaper |
author |
Ashley, Noah T. Ubuka, Takayoshi Schwabl, Ingrid Goymann, Wolfgang Salli, Brady M. Bentley, George E. Buck, C. Loren |
author_facet |
Ashley, Noah T. Ubuka, Takayoshi Schwabl, Ingrid Goymann, Wolfgang Salli, Brady M. Bentley, George E. Buck, C. Loren |
author_sort |
Ashley, Noah T. |
title |
Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination |
title_short |
Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination |
title_full |
Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination |
title_fullStr |
Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination |
title_full_unstemmed |
Revealing a Circadian Clock in Captive Arctic-Breeding Songbirds, Lapland Longspurs ( Calcarius lapponicus ), under Constant Illumination |
title_sort |
revealing a circadian clock in captive arctic-breeding songbirds, lapland longspurs ( calcarius lapponicus ), under constant illumination |
publisher |
SAGE Publications |
publishDate |
2014 |
url |
http://dx.doi.org/10.1177/0748730414552323 http://journals.sagepub.com/doi/pdf/10.1177/0748730414552323 http://journals.sagepub.com/doi/full-xml/10.1177/0748730414552323 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Lapland |
genre_facet |
Arctic Lapland |
op_source |
Journal of Biological Rhythms volume 29, issue 6, page 456-469 ISSN 0748-7304 1552-4531 |
op_rights |
http://journals.sagepub.com/page/policies/text-and-data-mining-license |
op_doi |
https://doi.org/10.1177/0748730414552323 |
container_title |
Journal of Biological Rhythms |
container_volume |
29 |
container_issue |
6 |
container_start_page |
456 |
op_container_end_page |
469 |
_version_ |
1766334315061313536 |