Daily rhythms of oxygen consumption, body temperature, activity and melatonin in the Norwegian lemming Lemmus lemmus under northern summer photoperiod

Abraham Haim, Seppo Saarela, Esa Hohtola, Nava Zisapel

Research output: Contribution to journalArticlepeer-review

Abstract

Rodents inhabiting high latitudes, close to the Arctic Circle or above it, are exposed to near 24 h daylight during the summer season. An example to such rodent species is the Norwegian lemming Lemmus lemmus, which is distributed in northern Fennoscandia. We measured daily rhythms of heat production (VO 2), body temperature (T b), motor activity and melatonin secretion (measured from its metabolite 6-sulfatoximelatonin 6-SMT) in individuals exposed to natural day light, Oulu Finland, in August 1997 and at a controlled ambient temperature of 22°C. Our results show a daily rhythm of VO 2 with an acrophase at 04:00 h and minimal values measured at 16:00 h, with a significant difference (p<0.001) between mean day and night values. 6-SMT also shows a daily rhythm with maximal secretion during the dark phase 24:00 and 06:00 h in which total 6-SMT values were 2.92±1.1 and 3.87±1.2 ng, respectively. The lowest values were recorded at 12:00 h; 0.86±0.63 ng. These results suggest that lemmings show a VO 2 and melatonin daily rhythms, which seem to correlate with each other and it appears that melatonin secretion increases heat production.

Original languageEnglish
Pages (from-to)629-633
Number of pages5
JournalJournal of Thermal Biology
Volume29
Issue number7-8 SPEC. ISS.
DOIs
StatePublished - Oct 2004

Keywords

  • Heat production
  • Melatonin
  • Photophase
  • Scotophase
  • Thermoregulation

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Agricultural and Biological Sciences (all)
  • Developmental Biology

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