Summer and winter cycles in plasma melatonin levels in the elephant seal (Mirounga Leonina)

Plasma melatonin concentration of immature male elephant seals was determined by radioimmunoassay. Comparison of concentrations during two 24-h periods, one in midsummer and one in midwinter, showed that there was a marked circadian cycle in winter which was greatly modified during the long day leng...

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Bibliographic Details
Published in:Australian Journal of Biological Sciences
Main Authors: Griffiths, D., Bryden, M. M., Seamark, R. F.
Format: Article in Journal/Newspaper
Language:English
Published: CSIRO Publishing 1979
Subjects:
Biotechnology
Developmental Biology
Animal Science and Zoology
General Materials Science
Genetics
Molecular Biology
Endocrinology
Reproductive Medicine
General Medicine
2700 Medicine
Midwinter
Elephant Seal
Elephant Seals
Mirounga leonina
Online Access:https://espace.library.uq.edu.au/view/UQ:ba241f9
Description
Summary:Plasma melatonin concentration of immature male elephant seals was determined by radioimmunoassay. Comparison of concentrations during two 24-h periods, one in midsummer and one in midwinter, showed that there was a marked circadian cycle in winter which was greatly modified during the long day length of summer. It is suggested that in summer there was sufficient ambient lighting during the night hours to depress the nocturnal rise in plasma melatonin. The complexity of pineal cycles in the natural environment is stressed, and in this regard the polar regions are of particular interest due to the extreme seasonal changes in day length there.

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