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Melatonin rhythms in the Australian freshwater crocodile(Crocodylus johnstoni): a reptile lacking a pineal complex?

Firth, Bruce T., Christian, Keith A., Belan, Ingrid and Kennaway, David J. (2010). Melatonin rhythms in the Australian freshwater crocodile(Crocodylus johnstoni): a reptile lacking a pineal complex?. Journal of Comparative Physiology B: biochemical systemic and environmental physiology,180(1):67-72.

Document type: Journal Article

IRMA ID 81704288xPUB158
Title Melatonin rhythms in the Australian freshwater crocodile(Crocodylus johnstoni): a reptile lacking a pineal complex?
Author Firth, Bruce T.
Christian, Keith A.
Belan, Ingrid
Kennaway, David J.
Journal Name Journal of Comparative Physiology B: biochemical systemic and environmental physiology
Publication Date 2010
Volume Number 180
Issue Number 1
ISSN 0174-1578   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-73949101993
Start Page 67
End Page 72
Total Pages 6
Place of Publication Germany
Publisher Springer
HERDC Category C1 - Journal Article (DIISR)
Abstract The vertebrate pineal gland is the primary source of melatonin, the rhythmic secretion of which is influenced by environmental light and temperature, thereby providing animals with information about seasonally changing photoperiod and thermoperiod. Although pineal glands are present in the majority of vertebrate species, a discrete organ is reported to be absent in the Crocodilia. However, if the melatonin rhythm is crucial to the survival of the organism, it would be expected that the rhythm would be present in crocodiles. In the present study, we measured blood plasma melatonin over a 30-h period in aestivating Australian freshwater crocodiles (Crocodylus johnstoni) in their natural habitat at the end of the dry season (November) and found no discernible melatonin rhythm. However, another group of captive-reared C. johnstoni, maintained under natural light and temperature cycles and sampled in the early dry season (June) showed a clear melatonin rhythm. These results suggest that there is either an extrapineal source of melatonin in this crocodile species or that there is melatonin producing tissue elsewhere which heretofore has not been discovered. Further studies are needed to determine why the melatonin rhythm is intermittently expressed and whether this may be related to seasonal changes in the expression of the rhythm linked to tropical environments.
Keywords Crocodylus johnstoni
Freshwater crocodile
Melatonin rhythm
Pineal gland
DOI http://dx.doi.org/10.1007/s00360-009-0387-8   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
 
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