Metabolic and insulative changes in winter- and summer-acclimatized King Penguin chicks

Abstract

Summary. The effect of photoperiod and cold on metabolic and insulative changes was investigated in winter-and summer-acclimatized King Penguin chicks under natural conditions (in subantarctic climate). Non-shivering thermogenesis was also studied.Metabolic rate of winter-fasting huddling chicks was compared to that of experimental summer-fasting chicks. Metabolic rate was estimated from measurements of loss in body mass and from measurements of 0 2 consumption and CO2 production at different ambient temperatures (from -40 to + 40 ~ Shivering activity was estimated. 1. The resting metabolic rate (RMR) at thermoneutrality (Fig. 5) was lower (-18%) during winter (2.l 5 W. kg-1) than during summer (2.63 W.kg-1). The lower critical temperature of the winter-chicks was lower (LCT = --10 ~ than in summer-chicks (LCT = 4.8 ~ 2. The thermal conductance in summer-acclimatized chicks (1.78 W.m -2" ~ at the LCT) is in the range of that of other large birds (Table 1). However, in winter-acclimatized chicks it is 48% less, which makes it the lowest (0.93 W-m -zo C-1) among the large birds.3. Huddling behavior allows the winter-acclimatized chicks to decrease metabolic rate below the RMR and to increase the length of total fasting (84_+ 3 days in winter v.s. 44__+ 3 days in summer).

Increase in the adenine nucleotide translocase content of duckling subsarcolemmal mitochondria during cold acclimation

“…This is in agreement with the loosely isolated mitochondria described in the skeletal muscle of cold-acclimated birds [5^8]. Fatty acids have been suggested to be involved [6,9,10] in such thermoregulatory uncoupling, which was also postulated in mammals [9,11^13]. However, such a thermogenic mechanism would lead to depressed mitochondrial ATP production and would in turn challenge all the ATP-consuming processes within muscle.…”

Increase in the adenine nucleotide translocase content of duckling subsarcolemmal mitochondria during cold acclimation

“…This is in agreement with the loosely isolated mitochondria described in the skeletal muscle of cold-acclimated birds [5^8]. Fatty acids have been suggested to be involved [6,9,10] in such thermoregulatory uncoupling, which was also postulated in mammals [9,11^13]. However, such a thermogenic mechanism would lead to depressed mitochondrial ATP production and would in turn challenge all the ATP-consuming processes within muscle.…”

Emperor penguin’s fossil relatives inhabited subtropical waters

“…Today, Aptenodytes is limited to far colder sea-surface temperatures, with individuals at the lowest latitudes in their range (i.e., Crozet Islands, 46.1°S) being exposed to temperatures of 3–10°C while foraging (Guinet et al, 1997; Huang et al, 2021; Pütz et al, 2021). Our results suggest that the warmer temperatures modelled for 2100 and beyond (Burke et al, 2018) are not direct constraints on the geographic range of Aptenodytes penguins, especially considering that the upper critical temperatures of the two extant species are up to 20°C higher than the sea-surface temperatures in which they forage (Pinshow et al, 1976; Barré, 1984; Froget et al, 2002; Lewden et al, 2020).…”

Energetics of Free-Ranging Seabirds

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Increase in the adenine nucleotide translocase content of duckling subsarcolemmal mitochondria during cold acclimation

“…This is in agreement with the loosely isolated mitochondria described in the skeletal muscle of cold-acclimated birds [5^8]. Fatty acids have been suggested to be involved [6,9,10] in such thermoregulatory uncoupling, which was also postulated in mammals [9,11^13]. However, such a thermogenic mechanism would lead to depressed mitochondrial ATP production and would in turn challenge all the ATP-consuming processes within muscle.…”

Emperor penguin’s fossil relatives inhabited subtropical waters

“…Today, Aptenodytes is limited to far colder sea-surface temperatures, with individuals at the lowest latitudes in their range (i.e., Crozet Islands, 46.1°S) being exposed to temperatures of 3–10°C while foraging (Guinet et al, 1997; Huang et al, 2021; Pütz et al, 2021). Our results suggest that the warmer temperatures modelled for 2100 and beyond (Burke et al, 2018) are not direct constraints on the geographic range of Aptenodytes penguins, especially considering that the upper critical temperatures of the two extant species are up to 20°C higher than the sea-surface temperatures in which they forage (Pinshow et al, 1976; Barré, 1984; Froget et al, 2002; Lewden et al, 2020).…”

Energetics of Free-Ranging Seabirds

“……”

Increase in the adenine nucleotide translocase content of duckling subsarcolemmal mitochondria during cold acclimation

“…This is in agreement with the loosely isolated mitochondria described in the skeletal muscle of cold-acclimated birds [5^8]. Fatty acids have been suggested to be involved [6,9,10] in such thermoregulatory uncoupling, which was also postulated in mammals [9,11^13]. However, such a thermogenic mechanism would lead to depressed mitochondrial ATP production and would in turn challenge all the ATP-consuming processes within muscle.…”

Emperor penguin’s fossil relatives inhabited subtropical waters

“…Today, Aptenodytes is limited to far colder sea-surface temperatures, with individuals at the lowest latitudes in their range (i.e., Crozet Islands, 46.1°S) being exposed to temperatures of 3–10°C while foraging (Guinet et al, 1997; Huang et al, 2021; Pütz et al, 2021). Our results suggest that the warmer temperatures modelled for 2100 and beyond (Burke et al, 2018) are not direct constraints on the geographic range of Aptenodytes penguins, especially considering that the upper critical temperatures of the two extant species are up to 20°C higher than the sea-surface temperatures in which they forage (Pinshow et al, 1976; Barré, 1984; Froget et al, 2002; Lewden et al, 2020).…”

Energetics of Free-Ranging Seabirds

“……”