Daily regulation of body temperature rhythm in the camel (Camelus dromedarius) exposed to experimental desert conditions

Abstract

In the present work, we have studied daily rhythmicity of body temperature (Tb) in Arabian camels challenged with daily heat, combined or not with dehydration. We confirm that Arabian camels use heterothermy to reduce heat gain coupled with evaporative heat loss during the day. Here, we also demonstrate that this mechanism is more complex than previously reported, because it is characterized by a daily alternation (probably of circadian origin) of two periods of poikilothermy and homeothermy. We also show that dehydration induced a decrease in food intake plays a role in this process. Together, these findings highlight that adaptive heterothermy in the Arabian camel varies across the diurnal light–dark cycle and is modulated by timing of daily heat and degrees of water restriction and associated reduction of food intake. The changed phase relationship between the light–dark cycle and the Tb rhythm observed during the dehydration process points to a possible mechanism of internal desynchronization during the process of adaptation to desert environment. During these experimental conditions mimicking the desert environment, it will be possible in the future to determine if induced high‐amplitude ambient temperature (Ta) rhythms are able to compete with the zeitgeber effect of the light–dark cycle.

Daily rhythms of physiological parameters in the dromedary camel under natural and laboratory conditions

“…Our results confirm previous demonstrations of robust daily rhythmicity of core body temperature in camels (Bligh and Harthoorn, 1965;Bouâouda et al, 2014;El-Allali et al, 2013).…”

“…The lower temperature in the study by Bligh and Harthoorn (1965) can be explained by the fact that they measured body temperature in the camel's hump, whereas Bouâouda et al (2014) The robustness of the core body temperature rhythm was between 40 and 80%, depending on whether it was calculated for individual animals or for the group as a whole, which is consistent with the findings in sheep, goats, horses, and cattle (Piccione et al, 2003). When the animals were maintained in a stable environment (without a light-dark cycle or a cycle of ambient temperature), core body temperature still exhibited near-24-hour rhythmicity, thus confirming the endogenous nature of the rhythm previously documented in a large number of species (Refinetti, 2010), including the camel (El-Allali et al, 2013).…”

“…Although Bligh and Harthoorn (1965) and Bouâouda et al (2014) found the mean core body temperature of the camel to be considerably lower (around 37.0 °C) than we did (38.0 °C), El-Allali et al (2013) obtained a mean very similar to the one we obtained (37.9 °C). The lower temperature in the study by Bligh and Harthoorn (1965) can be explained by the fact that they measured body temperature in the camel's hump, whereas Bouâouda et al (2014) The robustness of the core body temperature rhythm was between 40 and 80%, depending on whether it was calculated for individual animals or for the group as a whole, which is consistent with the findings in sheep, goats, horses, and cattle (Piccione et al, 2003).…”

“…In the camel, in particular, only a few studies have examined daily rhythmicity, and they focused on individual variables such as body temperature (Bligh and Harthoorn, 1965;Bouâouda et al, 2014;El-Allali et al, 2013), sweat rate (Abdoun et al, 2012), plasma aldosterone (Khaldoun et al, 2002), plasma melatonin (El-Allali et al, 2005), and biomarkers of bone formation (Al-Sobayil, 2010).…”

Arabian Oryx (Oryx leucoryx) Respond to Increased Ambient Temperatures with a Seasonal Shift in the Timing of Their Daily Inactivity Patterns

“…has not yet been shown (El Allali et al, 2013;Bouaouda et al, 2014). Our year round analysis and the analysis of the Arabian oryx in the South African summer, suggests that temperature is the driving force behind this change, whereas day length and rainfall appear to have little or no role.…”