Aspects of heterothermy in four species of afrotropical bats
- Authors: Doty, Anna Catherine
- Date: 2012
- Subjects: Body temperature -- Regulation , Afrotropical mammals , Body temperature , Bats
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10691 , http://hdl.handle.net/10948/d1008402 , Body temperature -- Regulation , Afrotropical mammals , Body temperature , Bats
- Description: Torpor and hibernation, two distinct forms of heterothermy, are physiological responses employed by many endotherms to save energy during periods of cold, climatic unpredictability and food shortage. Heterothermy is characterized by varying body temperature and has been found to occur in various subtropical mammals. However, studies on thermoregulatory capabilities of South African Microchiroptera remain relatively scant. In this study, the capacity for use of heterothermy, the seasonal metabolic rates, and capacity for non-shivering thermogenesis were studied in four species of bats, namely Rhinolophus clivosus, Rhinolophus capensis, Miniopterus natalensis and Myotis tricolor. Animals were collected from a group of three mines in Sleepy Hollow Farm, 30km from Port Elizabeth, South Africa. All species demonstrated bouts of torpor in the winter while R. clivosus interestingly established a high propensity for torpor in the summer and normothermia in the winter. To my knowledge, this is the first study that has shown the down-regulation of metabolism and body temperature in summer and constant maintenance of normothermic body temperature in winter in a species of Microchiroptera. M. natalensis was thermolabile in both summer and winter and body temperatures closely tracked ambient temperatures. Mean ± SD normothermic body temperature measured of wild-caught R. clivosus and M. natalensis was 38.6 ± 1.7°C and 37.3 ± 2.2°C, respectively. Mean torpid body temperature measured of wild-caught R. clivosus, R. capensis and M. natalensis was 22.7 ± 3.3°C, 21.1 ± 3.2 °C, and 22.6 ± 3.1°C, respectively. Non-shivering thermogenesis was measured in R. clivosus and M. natalensis to determine the role of endogenous heat production in a volant mammal. The mean noradrenalineinduced thermogenesis ± SD in R. clivosus and M. natalensis was 2.6 ± 0.8 ml g-1 hr-1 and 2.7 ± 0.6 ml O2 g-1 hr-1, respectively. Both species demonstrated capacity for non-shivering thermogenesis, and this is the first study that has quantified the maximal response to noradrenaline in an Afrotropical Microchiropteran species. Physiology of Afrotropical bats is understudied and the extent to which torpor and/or hibernation is utilized amongst them remains relatively unknown. Heterothermy clearly plays a significant role in the energetic savings and balance of all four species in the study.
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- Date Issued: 2012
Influence of macro- versus microcooling on the physiological and psychological performance of the human operator
- Authors: Heyns, Gerhardus Johannes
- Date: 1995
- Subjects: Cold -- Physiological effect , Temperature -- Physiological effect , Body temperature -- Regulation , Heat -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5167 , http://hdl.handle.net/10962/d1016247
- Description: This study evaluated the effect of a macro- versus a microcooling system on the cognitive, psychomotor and physiological performance of human operators. Male subjects (n = 24) were acclimatized for four days and then subjected to three different environmental conditions: hot ambient (40°C; 40% RH), microcooling and macrocooling. Each environmental condition was repeated twice; once under a rest condition and once while simulating a physical workload of 40 W. Four performance tests (reasoning, eye-hand coordination, memory, reaction time) were conducted once every hour for four hours. Five physiological measurements, viz rectal temperature, skin temperature, heart rate, total sweat loss and sweat rate, were taken. A significant difference existed between the physiological responses under the hot ambient condition and both cooling conditions. For all five physiological parameters he human operator benefitted substantially whatever the cooling condition. The psychological performance results indicated a greater benefit under the cooling conditions, though various external factors may have influenced responses. User perception showed that macrocooling was perceived to be the optimal method of cooling. The results showed that there was no difference in the extent to which both rectal temperature and heart rate (for rest and work conditions) decreased over the 4-hour study period with micro- and macrocooling. In the baseline hot environment both increase. Sweat rate was lowest when resting or working in a microcooled environment and at its highest in the hot baseline environment. Mean skin temperature was lowest (for rest and work conditions) with microcooling and highest in the hot baseline environment. Reaction time and memory/attention were the same under all three environmental conditions. Eye-hand coordination was better with cooling than without, but did not differ between the two cooling conditions. Reasoning ability was poorest under the hot baseline condition and best in the macrocooled environment. User perception showed that the subjects found macrocooling highly acceptable. Microcooling was found to be uncomfortable, particularly because cold air (18 - 21°C) entered the jacket at one point which caused numbness of the skin at that point. Jackets did not always fit subjects well and the umbilical cord restricted free movement.
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- Date Issued: 1995