Absence of Daily Rhythms of Prolactin and Corticosterone in Adélie Penguins Under Continuous Daylight

Vleck, Carol M.; Hook, Jessamyn A. Van

doi:10.1650/0010-5422(2002)104[0667:aodrop]2.0.co;2

Cited by 17 publications

(19 citation statements)

References 28 publications

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“…Untransformed concentrations of plasma corticosterone (ng/ml) (mean = 1.05, SD = 1.44, range = 0.02-11.36) and faecal tetrahydrocorticosterone (ng/g) (mean = 465.04, SD = 270.58, range = 41.18-1487.70) were within the ranges of concentrations which other studies have reported for plasma corticosterone (McQueen et al, 1999;Vleck & Van Hook, 2002;Vleck et al, 2000) and faecal tetrahydrocorticosterone (Nakagawa et al, 2003) in Adelie penguins.…”

Section: Plasma Corticosterone and Faecal Tetrahydrocorticosteronesupporting

confidence: 69%

“…Samples were collected at various times of the day (0900-2000 h), however circadian rhythms in hormone concentrations were unlikely to have produced any within-day variation due to the continuous 24 h daylight (Ringer, 1976 and references therein); furthermore, Vleck and Van Hook (2002) found no evidence that circadian rhythms operate in Adelie penguins in this context.…”

Section: Sample Collectionmentioning

confidence: 95%

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Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

et al. 2009

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Abstract. Physiological measurements of both stress and sex hormones are often used to estimate the consequences of natural or human-induced change in ecological studies of various animals. Different methods of hormone measurement exist, potentially explaining variation in results across studies; methods should be cross-validated to ensure they correlate.We directly compared faecal and plasma hormone measurements for the first time in a wild free-living species, the Adelie penguin (Pygoscelis adeliae). Blood and faecal samples were simultaneously collected from individual penguins for comparison, and assayed for testosterone and corticosterone (or their metabolites). Sex differences and variability within each measure, and correlation of values across measures were compared. For both hormones, plasma samples showed greater variation than faecal samples. Males had higher mean corticosterone concentrations than females, but the difference was only statistically significant in faecal samples. Plasma testosterone, but not faecal testosterone, was significantly higher in males than females. Correlation between sample types was poor overall, and weaker in females than in males, perhaps because measures from plasma represent hormones that are both free and bound to globulins, whereas measures from faeces represent only the free portion. Faecal samples also represent a cumulative measure of hormones over time, as opposed to a plasma 'snapshot' concentration. Our data indicate that faecal sampling appears more suitable for assessing baseline hormone concentrations, while plasma sampling may best define immediate responses to environmental events. Consequently, future studies should ensure they select the most appropriate matrix and method of hormone measurement to answer their research questions.

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Section: Plasma Corticosterone and Faecal Tetrahydrocorticosteronesupporting

confidence: 69%

Section: Sample Collectionmentioning

confidence: 95%

Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

et al. 2009

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“…Blood sampling depended on the bird departure and therefore occurred at any time of the day. Note that in Adélie penguins, no daily rhythm of corticosterone secretion has been reported (Vleck and Van Hook, 2002;Angelier et al, 2008). Foraging decisions and physiology in penguins…”

Section: Study Protocolmentioning

confidence: 96%

Ecophysiological response of Adélie penguins facing an experimental increase in breeding constraints

Beaulieu

Spée

Lazin

et al. 2010

Journal of Experimental Biology

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SUMMARYForaging strategies play a key role in breeding effort. Little is known, however, about their connection with hormonal and nutritional states, especially when breeding constraints vary. Here, we experimentally increased foraging costs and thus breeding constraints by handicapping Adélie penguins (Pygoscelis adeliae) with dummy devices representing 3-4% of the penguins' crosssectional area. We examined food-related stress (via plasma corticosterone concentration) and nutritional state (via metabolite levels). Concurrently, we investigated the use of ecological niches via the isotopic signature of red blood cells indicating the trophic position ( 15 N) and the spatial distribution ( 13 C) of penguins. Handicapped birds performed ~70% longer foraging trips and lost ~60% more body mass than controls and their partners. However, corticosterone levels and the nutritional state were unchanged. The isotopic signature revealed that males and females differed in their foraging behaviour: upper trophic levels contributed more in the males' diet, who foraged in more pelagic areas. Handicapped and partner birds adopted the same strategy at sea: a shift towards higher  13C values suggested that they foraged in more coastal areas than controls. This change in foraging decisions may optimize feeding time by decreasing travelling time. This may partly compensate for the presumed lower foraging efficiency of handicapped birds and for the energetic debt of their partners who had to fast ~70% longer on the nest. We propose that this flexible use of ecological niches may allow birds facing increased breeding constraints to avoid chronic stress and to minimize the impact on their body condition.

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“…Activity and hormonal rhythms persist during the summer in some polar animals: bumble bees in the high Arctic continue to display rhythms of foraging (Stelzer and Chittka, 2010), a rhythm of melatonin release is observed in the willow warbler (Silverin et al, 2009) and in the Lapland longspur (Ashley et al, 2013), and a daily rhythm of body temperature is noted in Arctic ground squirrels during the summer (Williams et al, 2012), but in Antarctic penguins, rhythms of melatonin, prolactin (Miché et al, 1991;Cockrem, 1991) and corticosterone (Vleck and van Hook, 2002) appear to stop. Among four Arctic-breeding birds, substantial variation in daily activity rhythms are noted, depending on species, sex and breeding stage (Steiger et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Continuous activity and no cycling of clock genes in the Antarctic midge during the polar summer

Kobelková

Goto

Peyton

et al. 2015

Journal of Insect Physiology

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The extreme seasonal shifts of day length in polar regions, ranging from constant light in the summer to constant darkness in the winter, pose an intriguing environment for probing activity rhythms and the functioning of circadian clocks. Here, we monitor locomotor activity during the summer on the Antarctic Peninsula and under laboratory conditions, as well as the accompanying patterns of clock gene expression in the Antarctic midge, the only insect endemic to Antarctica. Larvae and adults are most active during the warmest portion of the day, but at a constant temperature they remain continuously active regardless of the photoregime, and activity also persists in constant darkness. The canonical clock genes period, timeless, Clock, and vrille are expressed in the head but we detected no cycling of expression in either the field or under diverse photoregimes in the laboratory. The timekeeping function of the clock has possibly been lost, enabling the midge to opportunistically exploit the unpredictable availability of permissive thermal conditions for growth, development, and reproduction during the short summer in Antarctica.

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Absence of Daily Rhythms of Prolactin and Corticosterone in Adélie Penguins Under Continuous Daylight

Cited by 17 publications

References 28 publications

Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

Ecophysiological response of Adélie penguins facing an experimental increase in breeding constraints

Continuous activity and no cycling of clock genes in the Antarctic midge during the polar summer

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