Document Detail

Melatonin rhythms in the Australian freshwater crocodile (Crocodylus johnstoni): a reptile lacking a pineal complex?
MedLine Citation:
PMID:  19585125     Owner:  NLM     Status:  MEDLINE    
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.
Bruce T Firth; Keith A Christian; Ingrid Belan; David J Kennaway
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-07-08
Journal Detail:
Title:  Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology     Volume:  180     ISSN:  1432-136X     ISO Abbreviation:  J. Comp. Physiol. B, Biochem. Syst. Environ. Physiol.     Publication Date:  2010 Jan 
Date Detail:
Created Date:  2009-12-30     Completed Date:  2010-03-15     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8413200     Medline TA:  J Comp Physiol B     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  67-72     Citation Subset:  IM    
Discipline of Anatomical Sciences, Faculty of Health Sciences, School of Medical Sciences, University of Adelaide, Adelaide, SA, 5005, Australia.
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MeSH Terms
Adaptation, Biological
Alligators and Crocodiles / blood,  physiology*
Animals, Wild / blood,  physiology
Circadian Rhythm*
Fresh Water
Melatonin / blood*,  metabolism
Northern Territory
Reg. No./Substance:

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