Diel variations in plasma glucose concentration in some South African avian frugivores
Kerileigh Lobban A , Colleen Downs A B and Mark Brown AA School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg, 3209, South Africa.
B Corresponding author. Email: downs@ukzn.ac.za
Emu 110(1) 66-70 https://doi.org/10.1071/MU09088
Submitted: 3 September 2009 Accepted: 13 November 2009 Published: 24 February 2010
Abstract
We examined diel variations in the plasma glucose concentrations (PGlu) of avian blood, by measuring PGlu in four South African fruit-eating birds: the Cape White-eye (Zosterops virens), Knysna Turaco (Tauraco corythaix), Red-winged Starling (Onychognathus morio) and Speckled Mousebird (Colius striatus). Species were chosen as representatives of a range of body sizes and from the passerines and non-passerines. Birds were maintained in controlled environment rooms and PGlu were measured at four times of the day, at sunrise (0600 hours), midday (1200 hours), sunset (1800 hours) and midnight (2400 hours). Interspecific variation in mass and both the interspecific and intraspecific variation in PGlu were found to be significant for all species. PGlu of Red-winged Starlings and Knysna Turacos were highest after overnight fasting, whereas peak PGlu in Speckled Mousebirds and Cape White-eyes were recorded at midday. The lowest PGlu was recorded after overnight fasting in Speckled Mousebirds whereas the lowest PGlu were recorded at midnight in the three other species. Whereas the Red-winged Starlings, Knysna Turacos and Cape White-eyes clearly increase their PGlu via the processes of gluconeogenesis, Speckled Mousebirds apparently do not. Previous studies involving the comparison of avian PGlu have not specified sampling times and this study clearly demonstrates that PGlu of birds vary over time, thereby highlighting the need for the specification of sampling times in future sampling of avian PGlu.
Additional keywords: gluconeogenesis, glucoregulation, non-passerine, passerine.
Acknowledgements
Steven Gordon, Ryan Lobban, Sandra Hanafey and Clive Lobban are thanked for their support of Kerileigh Lobban. We are grateful to Amy Wilson, Tracy Odendaal and Ebrahim Ally for their invaluable assistance during the study. The study had ethical clearance from the University of KwaZulu-Natal Ethics Committee.
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