Diel pattern of corticosterone metabolites in Arctic barnacle goslings (Branta leucopsis) under continuous natural light

Abstract

Here we describe the excretion pattern of corticosterone metabolites collected from droppings in barnacle goslings (Branta leucopsis) raised under 24 hours of continuous natural light in the Arctic. In lower latitudes, circulating corticosterone peaks around waking and shows a nadir between midnight and 4:00, whereas the peak and nadir are time-delayed slightly when measuring corticosterone metabolites from droppings. Photoperiod, along with other environmental factors, helps to entrain an animal’s endogenous rhythm to that of the natural world. North of the Arctic Circle, photoperiod may not be a reliable cue as light is continuously absent during the winter and continuously present during the summer. Here, for the first time, we used droppings to describe a 24-hour excretion pattern of corticosterone metabolites (CORTm). By applying circular statistics for dependent data, we found a diel rhythmic pattern even under continuous natural light. We discuss potential alternative ‘Zeitgeber’ that may function even in the polar regions, focusing on melatonin. We propose a line of research to measure melatonin non-invasively from droppings. We also provide a validation of the adopted enzyme immunoassay (EIA) that was originally developed for greylag geese.

Melatonin and corticosterone profiles under polar day in a seabird with sexually opposite activity-rhythms

“…Weddell seals (Leptonychotes weddellii) gave a similar result for cortisol during polar day (Barrell and Montgomery, 1989). In contrast, a recent study of droppings of barnacle goslings (Branta leucopsis) detected weak diel rhythmicity in corticosterone metabolites (Scheiber et al, 2017).…”

“…Near the equator Nazca boobies maintained a diel profile of corticosterone, but the nocturnal rise disappeared under full moon conditions (Tarlow et al, 2003), while penguins and eider ducks residing under continuous light lacked diel variation in corticosterone (Steenweg et al, 2015;Vleck and van Hook, 2002; cf. the barnacle goslings, Scheiber et al, 2017). At least in some species, continuous light might directly or indirectly abolish diel rhythms in corticosterone.…”

Stress behaviour and physiology of developing Arctic barnacle goslings ( Branta leucopsis ) is affected by legacy trace contaminants

“…Hence, both studies strengthen the fact that baseline glucocorticoid level were not (yet) altered by the past contamination. In the arctic summer, barnacle goslings were shown to excrete CORTm in a phase-shifted diel pattern, which might be indicative of a pre-maturely developed HPA system subject to change in older goslings [42]. It is possible that a suppressive effect of (Hg) on baseline CORTm levels might only become evident once the HPA system shows the characteristic adult corticosterone secretion pattern.…”

The relationship between daily behavior, hormones, and a color dimorphism in a seabird under natural continuous light

“…Although glucocorticoids are known to be under the control of the circadian system in mammals (Dickmeis, 2009;Kalsbeek et al, 2012;Son et al, 2011), most studies of glucocorticoids during polar summer describe little to no variation across the diel cycle (birds: (Huffeldt et al, 2020;Steenweg et al, 2015;Vleck and van Hook, 2002) [cf. (Scheiber et al, 2017)]; mammals: (Barrell and Montgomery, 1989)). To gain better insight into the functional role of melatonin and corticosterone during the continuous light of polar summer, we studied these hormones in a seabird, the common murre (Uria aalge).…”