Adaptive heterothermy and selective brain cooling in arid-zone mammals

Mitchell, Duncan; Maloney, Shane K.; Jessen, Claus; Laburn, Helen P.; Kamerman, Peter R.; Mitchell, G.; Fuller, Andrea

doi:10.1016/s1096-4959(02)00012-x

Cited by 125 publications

(157 citation statements)

References 43 publications

Supporting

Mentioning

151

Contrasting

Unclassified

Order By: Relevance

“…In terms of the classic interpretation of adaptive heterothermy (sensu Mitchell et al, 2002), water use is reduced when water supply is limited and the phenomenon could be considered adaptive if the resulting higher T c was not more detrimental than the benefit of the water savings. The phenomenon could occur either as a direct response to water limitation, as in dehydration-induced hyperthermia, or as a more strategic response that may be linked to a seasonal rhythm.…”

Section: S K Maloney and Othersmentioning

confidence: 99%

Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?

Maloney

Fuller

Meyer

et al. 2011

Journal of Experimental Biology

Self Cite

View full text Add to dashboard Cite

SUMMARYUsing implanted temperature loggers, we measured core body temperature in nine western grey kangaroos every 5min for 24 to 98days in spring and summer. Body temperature was highest at night and decreased rapidly early in the morning, reaching a nadir at 10:00h, after ambient temperature and solar radiation had begun to increase. On hotter days, the minimum morning body temperature was lower than on cooler days, decreasing from a mean of 36.2°C in the spring to 34.0°C in the summer. This effect correlated better with the time of the year than with proximate thermal stressors, suggesting that either season itself or some factor correlated with season, such as food availability, caused the change. Water saving has been proposed as a selective advantage of heterothermy in other large mammals, but in kangaroos the water savings would have been small and not required in a reserve with permanent standing water. We calculate that the lower core temperature could provide energy savings of nearly 7%. It is likely that the heterothermy that we observed on hot days results either from decreased energy intake during the dry season or from a seasonal pattern entrained in the kangaroos that presumably has been selected for because of decreased energy availability during the dry season.

show abstract

Section: S K Maloney and Othersmentioning

confidence: 99%

Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?

Maloney

Fuller

Meyer

et al. 2011

Journal of Experimental Biology

Self Cite

View full text Add to dashboard Cite

show abstract

“…Many endotherms are thought to reduce this cost by storing heat (facultative hyperthermia) during periods of heat stress, thereby reducing the need for evaporative cooling at high T air (mammals, reviewed by Mitchell et al [2002], Cain et al [2006]; birds, reviewed by Tieleman and Williams [1999]). …”

Section: Introductionmentioning

confidence: 99%

Adaptive thermoregulation during summer in two populations of an arid‐zone passerine

Smit

Harding

Hockey

et al. 2013

Ecology

112

View full text Add to dashboard Cite

Abstract. Heterothermy plays an important role in lowering the costs of thermoregulation in endotherms by reducing water and energy requirements. We tested predictions that birds in arid habitats should express fine-scale variation in their thermoregulatory patterns as a function of prevailing climatic conditions. We assessed effects of air temperature (T air ) and water vapor pressure deficit (D) on body temperature (T b ) in free-living White-browed Sparrow-Weavers (Plocepasser mahali ) during summer in two arid habitats in the Kalahari Desert, South Africa, using data from a dry period at a hot, desert site (n ¼ 7 birds), and during a dry period (n ¼ 4 birds) and a wet period (n ¼ 5 birds) at a milder, semi-desert site. The desert birds maintained a significantly higher set-point T b (41.58 6 0.28C, mean 6 SD) than semi-desert birds (40.28 6 0.28C). During the warmest part of day (12:00-18:00 hours), T b increased significantly during periods of high T air and/or high humidity, and mean and maximum T b were up to 1.48 and 2.38C, respectively, above normal levels. However, as T air increased, birds at the desert site maintained T b at or below set-point levels for a greater proportion of the time than birds at the semi-desert site. Birds at the desert site also expressed a greater magnitude of daily heterothermy (heterothermy index, HI ¼ 2.48 6 0.38C, mean 6 SD) than birds at the semi-desert site: the latter population showed a greater magnitude of heterothermy during a dry period (HI ¼ 2.18 6 0.38C) than during a wet period (HI ¼ 1.68 6 0.28C). Birds continued foraging throughout the warmest part of the day, despite the fact that heat dissipation (percentage of time spent panting and wing-spreading) increased significantly with increasing T air . Our findings reveal that populations can vary in their thermoregulatory responses in both space and time and suggest that small changes in T air can have significant effects on thermoregulation in free-ranging desert birds, even when T air , T b . These data have important implications for assessing vulnerability of species to climate change, suggesting that sensitivity should be assessed at the population, rather than species, level.

show abstract

“…Cetaceans are under constant, significant thermal pressures due to their aquatic environment (Manger, 2006), whereas the artiodactyls have mechanisms in place to prevent overheating (Kuhnen, 1997;Jessen, 1998Jessen, , 2001Mitchell et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Orexinergic bouton density is lower in the cerebral cortex of cetaceans compared to artiodactyls

Dell

Spocter

Patzke

et al. 2015

Journal of Chemical Neuroanatomy

View full text Add to dashboard Cite

Highlights• The orexinergic innervation of the cerebral cortex of Cetartiodactyla is described.• All species show a similar innervation pattern.• The density of innervation is far less in cetaceans than artiodactyls. 1 AbstractThe species of the cetacean and artiodactyl suborders, which make up the cetartiodactyl order, have very different arousal thresholds and sleep-wake systems.The aim of this study was to determine whether cetaceans or artiodactyls have differently organized orexinergic arousal systems by examining the density of orexinergic innervation to the cerebral cortex. This study provides a comparison of orexinergic bouton density in the cerebral cortex of twelve cetartiodactyl species by means of immunohistochemical staining and stereological analysis. It was observed that the morphology of the axonal projections of the orexinergic system to the cerebral cortex was similar across all species, as the presence, size and proportion of large and small orexinergic boutons were similar. Despite this, orexinergic bouton density was lower in the cerebral cortex of cetaceans compared to artiodactyls, even when corrected for brain mass, neuron density, glial density and glial: neuron ratio. Glial density was identified as the major determinant for the observed differences. It appears a synergy exists between the orexinergic neurons and their projections, glial cells, and the biochemical correlates of appetitive drive and arousal, but further studies need to be performed to understand the full extent of the orexinergic system and its role in sustained arousal.

show abstract

Adaptive heterothermy and selective brain cooling in arid-zone mammals

Cited by 125 publications

References 43 publications

Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?

Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?

Adaptive thermoregulation during summer in two populations of an arid‐zone passerine

Orexinergic bouton density is lower in the cerebral cortex of cetaceans compared to artiodactyls

Contact Info

Product

Resources

About