Net superoxide levels: steeper increase with activity in cooler female and hotter male lizards.
Ectotherms increase their body temperature in response to ambient heat, thereby elevating their metabolic rate. An often inferred consequence of this is an overall upregulation of gene expression and energetic expenditure, and a concomitant increased production of reactive oxygen species (e.g. superoxide) and, perhaps, a shortened lifespan. However, recent work shows that this may be a superficial interpretation. For example, sometimes a reduced temperature may in fact trigger up-regulation of gene expression. We studied temperature and associated activity effects in male and female Australian painted dragon lizards (Ctenophorus pictus) by allowing the lizards to bask for 4 h versus 12 h, and scoring their associated activity (inactive versus active basking and foraging). As predicted, long-basking lizards (hereafter 'hot') showed heightened activity in both sexes, with a more pronounced effect in females. We then tested for sex-specific effects of basking treatment and activity levels on the increase in net levels of superoxide. In males, short-baskers (hereafter 'cold') had significantly more rapidly decreasing levels of superoxide per unit increasing activity than hot males. In females, however, superoxide levels increased faster with increasing activity in the cold than in the hot basking treatment, and females earlier in the ovarian cycle had lower superoxide levels than females closer to ovulation. In short, males and females differ in how their levels of reactive oxygen species change with temperature-triggered activity.
University of Sydney School of Biological Sciences, Heydon-Lawrence Building, NSW 2006, Australia. cissy.ballen@sydney.edu.au
Cissy
C
Ballen
Mo
M
Healey
Mark
M
Wilson
Michael
M
Tobler
Erik
E
Wapstra
Mats
M
Olsson
D000818:Animals; D001315:Australia; D001833:Body Temperature Regulation; D005260:Female; D008116:Lizards / Q000502:physiology*; D008297:Male; D009043:Motor Activity; D013481:Superoxides / Q000378:metabolism*; D013696:Temperature
D013481:Superoxides