Dataset Information

The role of ambient temperature and body mass on body temperature, standard metabolic rate and evaporative water loss in southern African anurans of different habitat specialisation.

ABSTRACT: Temperature and water availability are two of the most important variables affecting all aspects of an anuran's key physiological processes such as body temperature (T b), evaporative water loss (EWL) and standard metabolic rate (SMR). Since anurans display pronounced sexual dimorphism, evidence suggests that these processes are further influenced by other factors such as vapour pressure deficit (VPD), sex and body mass (M b). However, a limited number of studies have tested the generality of these results across a wide range of ecologically relevant ambient temperatures (T a), while taking habitat use into account. Thus, the aim of this study was to investigate the role of T a on T b, whole-animal EWL and whole-animal SMR in three wild caught African anuran species with different ecological specialisations: the principally aquatic African clawed frog (Xenopus laevis), stream-breeding common river frog (Amietia delalandii), and the largely terrestrial raucous toad (Sclerophrys capensis). Experiments were conducted at a range of test temperatures (5-35 °C, at 5 °C increments). We found that VPD better predicted rates of EWL than T a in two of the three species considered. Moreover, we found that T b, whole-animal EWL and whole-animal SMR increased with increasing T a, while T b increased with increasing M b in A. delalandii and S. capensis but not in X. laevis. Whole-animal SMR increased with increasing M b in S. capensis only. We did not find any significant effect of VPD, M b or sex on whole-animal EWL within species. Lastly, M b did not influence T b, whole-animal SMR and EWL in the principally aquatic X. laevis. These results suggest that M b may not have the same effect on key physiological variables, and that the influence of M b may also depend on the species ecological specialisation. Thus, the generality of M b as an important factor should be taken in the context of both physiology and species habitat specialisation.

SUBMITTER: Mokhatla M

PROVIDER: S-EPMC6814148 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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The role of ambient temperature and body mass on body temperature, standard metabolic rate and evaporative water loss in southern African anurans of different habitat specialisation.

Mokhatla Mohlamatsane M Measey John J Smit Ben B

PeerJ 20191022

Temperature and water availability are two of the most important variables affecting all aspects of an anuran's key physiological processes such as body temperature (T b), evaporative water loss (EWL) and standard metabolic rate (SMR). Since anurans display pronounced sexual dimorphism, evidence suggests that these processes are further influenced by other factors such as vapour pressure deficit (VPD), sex and body mass (M b). However, a limited number of stud ...[more]

PMID: 31660269

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Project description:Valery M. Gavrilov (2017) Total evaporative water loss (TEWL) in Passeriformes and Non-Passeriformes was estimated by simultaneous measurements of energy expenditure and mass loss in resting birds. It was found that the percentage of heat dissipated by water evaporation depends on body size. Published data for 102 bird species were analyzed together with my own measurements for 157 bird species at thermally neutral temperatures (mostly 25°C) to establish the following relationship between TEWL and body mass: TEWL25°C Aves = 0.28 m0.701, R 2 = 0.92, where TEWL is in g H2O/day and m is body mass (g). The scaling exponent 0.701 ± 0.007 is 0.05 greater than for the relationship of basal metabolic rate (BMR) to body mass. It was found that TEWL in passerines is higher than in non-passerines at all ambient temperatures by 50% at 25°C, 30% at 0°C, 39% at the lower critical temperature, and 59% at the upper critical temperature. The dependence of water loss on body mass at different ambient temperatures (T A) was found to vary in the same manner as evaporative heat loss. TEWL in Passeriformes is approximately 25-60% higher than in Non-Passeriformes (particularly at high T A), which is consistent with the ratio of their BMR levels. Within the thermoneutral zone, the proportion of heat dissipated by evaporation increases by approximately 2.6-fold in small passerines and by almost 4.1-fold in large passerines with the transition from the lower to upper critical temperature. In non-passerines, the proportion of evaporative heat losses increases by approximately 2.7 times within the thermoneutral zone in both large and small birds. The high basal metabolic rate in Passeriformes involves benefits like a higher maximum metabolic power and the ability to breed at lower ambient temperatures, but it comes with a cost: a significant expenditure of evaporative water. This cost is important because it is found to increase with body size in Passeriformes due to the forced evaporative heat loss, but it shows virtually no increase with body size in Non-Passeriformes. Thus, despite a high BMR significantly increasing ecological opportunities, this way of expanding the ecological niches is possible for the small size class only. These findings suggest that the high level of basal metabolic rate in Passeriformes in comparison to Non-Passeriformes determines the necessity for the former to utilize considerably larger amounts of water for evaporation to maintain the needed heat balance, especially at higher ambient temperatures and at larger body sizes.

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Dataset Information

The role of ambient temperature and body mass on body temperature, standard metabolic rate and evaporative water loss in southern African anurans of different habitat specialisation.

Publications

The role of ambient temperature and body mass on body temperature, standard metabolic rate and evaporative water loss in southern African anurans of different habitat specialisation.

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