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Torpor on demand: heterothermy in the non-lemur primate Galago moholi.

Nowack J, Mzilikazi N, Dausmann KH - PLoS ONE (2010)

Bottom Line: However they do not use it as a routine behaviour, but only under adverse conditions.This reluctance is presumably a result of conflicting selective pressures for energy savings versus other ecological and evolutionary forces, such as reproduction or territory defence.Our results support the view that heterothermy in primates evolved before the division of African and Malagasy Strepsirhini, with the possible implication that more primate species than previously thought might still have the potential to call upon this possibility, if the situation necessitates it.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Ecology and Conservation, Biocentre Grindel, University of Hamburg, Hamburg, Germany. julia.nowack@uni-hamburg.de

ABSTRACT

Background: Hibernation and daily torpor are energy- and water-saving adaptations employed to survive unfavourable periods mostly in temperate and arctic environments, but also in tropical and arid climates. Heterothermy has been found in a number of mammalian orders, but within the primates so far it seems to be restricted to one family of Malagasy lemurs. As currently there is no evidence of heterothermy of a primate outside of Madagascar, the aim of our study was to investigate whether small primates from mainland Africa are indeed always homeothermic despite pronounced seasonal changes in weather and food availability.

Methodology/principal findings: One of the nearest relatives of Malagasy lemurs, the African lesser bushbaby, Galago moholi, which inhabits a highly seasonal habitat with a hot wet-season and a cold dry-season with lower food abundance, was investigated to determine whether it is capable of heterothermy. We measured skin temperature of free-ranging individuals throughout the cool dry season using temperature-sensitive collars as well as metabolic rate in captured individuals. Torpor was employed by 15% of 20 animals. Only one of these animals displayed heterothermy in response to natural availability of food and water, whereas the other animals became torpid without access to food and water.

Conclusions/significance: Our results show that G. moholi are physiologically capable of employing torpor. However they do not use it as a routine behaviour, but only under adverse conditions. This reluctance is presumably a result of conflicting selective pressures for energy savings versus other ecological and evolutionary forces, such as reproduction or territory defence. Our results support the view that heterothermy in primates evolved before the division of African and Malagasy Strepsirhini, with the possible implication that more primate species than previously thought might still have the potential to call upon this possibility, if the situation necessitates it.

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Metabolic rate and skin temperature of a sub adult female G.moholi including a torpor bout.Skin temperature (Tskin) started dropping below 30°C in the morning at 5:30am; Metabolic rate () started decreasing earlier at 4am. The female was torpid for about six hours. Grey area illustrates , black line shows Tskin, dotted line indicates the period of artificial variations in Tskin measurements due to movements of the animal, dashed line shows ambient temperature in the laboratory room (Ta); black bar indicates the dark phase, white bars indicate the daytime.
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pone-0010797-g002: Metabolic rate and skin temperature of a sub adult female G.moholi including a torpor bout.Skin temperature (Tskin) started dropping below 30°C in the morning at 5:30am; Metabolic rate () started decreasing earlier at 4am. The female was torpid for about six hours. Grey area illustrates , black line shows Tskin, dotted line indicates the period of artificial variations in Tskin measurements due to movements of the animal, dashed line shows ambient temperature in the laboratory room (Ta); black bar indicates the dark phase, white bars indicate the daytime.

Mentions: Two out of twelve animals (female, sb; juvenile with uncertain sex) entered torpor during MR measurement in the laboratory, presumably as a reaction to food and water restriction. Both incidences occurred between the 12th and 16th of April 2009. The minimum Tskin recorded was 21.8°C (female, 180 g) closely reflecting Ta and 25.9°C (juvenile, 95 g). MR started decreasing about 60 min before Tskin.. For the female, the minimal oxygen consumption () during torpor was only 1/10th (0.09 ml g−1 h−1, Tskin 22.8±1.8°C, Ta 22.2±0.7°C) of minimal during normothermic resting conditions (0.99 ml g−1 h−1, Tskin 35.3±0.7°C, Ta 28±0.2°C) (fig. 2). The torpor bout was initiated around 5:30am and was terminated by the animal around 12pm. The energy savings of the juvenile during torpor were not as pronounced, with decreasing down to a value of 0.4 ml g−1 h−1 (Tskin 26.4°C±0.5°C, Ta 23.3±1.5°C), which was a 32% reduction of energy expenditure (1.23 ml g−1 h−1 under normothermic resting conditions, Tskin 34.4±0.3°C, Ta 27.3±0.4°C). This animal was disturbed before it spontaneously terminated its torpor bout after about 4.5 hours at 11pm with a Tskin of 27°C.


Torpor on demand: heterothermy in the non-lemur primate Galago moholi.

Nowack J, Mzilikazi N, Dausmann KH - PLoS ONE (2010)

Metabolic rate and skin temperature of a sub adult female G.moholi including a torpor bout.Skin temperature (Tskin) started dropping below 30°C in the morning at 5:30am; Metabolic rate () started decreasing earlier at 4am. The female was torpid for about six hours. Grey area illustrates , black line shows Tskin, dotted line indicates the period of artificial variations in Tskin measurements due to movements of the animal, dashed line shows ambient temperature in the laboratory room (Ta); black bar indicates the dark phase, white bars indicate the daytime.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2875402&req=5

pone-0010797-g002: Metabolic rate and skin temperature of a sub adult female G.moholi including a torpor bout.Skin temperature (Tskin) started dropping below 30°C in the morning at 5:30am; Metabolic rate () started decreasing earlier at 4am. The female was torpid for about six hours. Grey area illustrates , black line shows Tskin, dotted line indicates the period of artificial variations in Tskin measurements due to movements of the animal, dashed line shows ambient temperature in the laboratory room (Ta); black bar indicates the dark phase, white bars indicate the daytime.
Mentions: Two out of twelve animals (female, sb; juvenile with uncertain sex) entered torpor during MR measurement in the laboratory, presumably as a reaction to food and water restriction. Both incidences occurred between the 12th and 16th of April 2009. The minimum Tskin recorded was 21.8°C (female, 180 g) closely reflecting Ta and 25.9°C (juvenile, 95 g). MR started decreasing about 60 min before Tskin.. For the female, the minimal oxygen consumption () during torpor was only 1/10th (0.09 ml g−1 h−1, Tskin 22.8±1.8°C, Ta 22.2±0.7°C) of minimal during normothermic resting conditions (0.99 ml g−1 h−1, Tskin 35.3±0.7°C, Ta 28±0.2°C) (fig. 2). The torpor bout was initiated around 5:30am and was terminated by the animal around 12pm. The energy savings of the juvenile during torpor were not as pronounced, with decreasing down to a value of 0.4 ml g−1 h−1 (Tskin 26.4°C±0.5°C, Ta 23.3±1.5°C), which was a 32% reduction of energy expenditure (1.23 ml g−1 h−1 under normothermic resting conditions, Tskin 34.4±0.3°C, Ta 27.3±0.4°C). This animal was disturbed before it spontaneously terminated its torpor bout after about 4.5 hours at 11pm with a Tskin of 27°C.

Bottom Line: However they do not use it as a routine behaviour, but only under adverse conditions.This reluctance is presumably a result of conflicting selective pressures for energy savings versus other ecological and evolutionary forces, such as reproduction or territory defence.Our results support the view that heterothermy in primates evolved before the division of African and Malagasy Strepsirhini, with the possible implication that more primate species than previously thought might still have the potential to call upon this possibility, if the situation necessitates it.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Ecology and Conservation, Biocentre Grindel, University of Hamburg, Hamburg, Germany. julia.nowack@uni-hamburg.de

ABSTRACT

Background: Hibernation and daily torpor are energy- and water-saving adaptations employed to survive unfavourable periods mostly in temperate and arctic environments, but also in tropical and arid climates. Heterothermy has been found in a number of mammalian orders, but within the primates so far it seems to be restricted to one family of Malagasy lemurs. As currently there is no evidence of heterothermy of a primate outside of Madagascar, the aim of our study was to investigate whether small primates from mainland Africa are indeed always homeothermic despite pronounced seasonal changes in weather and food availability.

Methodology/principal findings: One of the nearest relatives of Malagasy lemurs, the African lesser bushbaby, Galago moholi, which inhabits a highly seasonal habitat with a hot wet-season and a cold dry-season with lower food abundance, was investigated to determine whether it is capable of heterothermy. We measured skin temperature of free-ranging individuals throughout the cool dry season using temperature-sensitive collars as well as metabolic rate in captured individuals. Torpor was employed by 15% of 20 animals. Only one of these animals displayed heterothermy in response to natural availability of food and water, whereas the other animals became torpid without access to food and water.

Conclusions/significance: Our results show that G. moholi are physiologically capable of employing torpor. However they do not use it as a routine behaviour, but only under adverse conditions. This reluctance is presumably a result of conflicting selective pressures for energy savings versus other ecological and evolutionary forces, such as reproduction or territory defence. Our results support the view that heterothermy in primates evolved before the division of African and Malagasy Strepsirhini, with the possible implication that more primate species than previously thought might still have the potential to call upon this possibility, if the situation necessitates it.

Show MeSH
Related in: MedlinePlus