Seasonal thermoregulation in the burrowing parrot (Cyanoliseus patagonus)

Birds exposed to seasonal environments are faced with the problem of maintaining thermogenic homoeostasis. Previous studies have established that birds native to the Holarctic increase their Resting Metabolic Rate at different ambient temperatures (RMR_Ta) and Basal Metabolic Rate (BMR) in winter as an adaptation to cold temperature since winters are more severe, while their non-Holarctic counterparts generally decrease their winter BMR as an energy saving mechanism during unproductive and dry winter months. In this study, we examined seasonal thermoregulation in the burrowing parrot (Cyanoliseus patagonus), a colonial psittacine native to the Patagonian region of Argentina, a region with an unpredictable environment. We found significantly higher mass specific RMR_Ta and BMR in summer than in winter. Both summer and winter BMR of the species fell within the predicted 95% confident interval for a parrot of its size. Body mass was significantly higher in winter than in summer. The burrowing parrot had broad thermo-neutral zones in winter and summer. The circadian rhythm of core body temperature (T_b) of burrowing parrots was not affected by season, showing that this species regulated its T_b irrespective of season. These results suggest that the burrowing parrots' seasonal thermoregulatory responses represent that of energy conservation which is important in an unpredictable environment.     

Seasonal effects on metabolism and thermoregulation abilities of the Red-winged Starling (Onychognathus morio)

Basal metabolic rate (BMR) of birds is beginning to be viewed as a highly flexible physiological trait influenced by environmental fluctuations, and in particular changes in ambient temperatures (T_a). Southern Africa is characterized by an unpredictable environment with daily and seasonal variation. This study sought to evaluate the effects of seasonal changes in T_a on mass-specific resting metabolic rate (RMR), BMR and body temperature (T_b) of Red-winged Starlings (Onychognathus morio). They have a broad distribution, from Ethiopia to the Cape in South Africa and are medium-sized frugivorous birds. Metabolic rate (VO₂) and T_b were measured in wild caught Red-winged Starlings after a period of summer and winter acclimatization in outdoor aviaries. RMR and BMR were significantly higher in winter than summer. Body mass of Starlings was significantly higher in winter compared with summer. The increased RMR and BMR in winter indicate improved ability to cope with cold and maintenance of a high T_b. These results show that the metabolism of Red-winged Starlings are not constant, but exhibit a pronounced seasonal phenotypic flexibility with maintenance of a high T_b.     

Seasonal variation in the metabolism-temperature relation of House Sparrows (Passer domesticus) in KwaZulu-Natal,South Africa

Many birds exhibit considerable phenotypic flexibility in metabolism to maintain thermoregulation or to conserve energy. This flexibility usually includes seasonal variation in metabolic rate. Seasonal changes in physiology and behavior of birds are considered to be a part of their adaptive strategy for survival and reproductive success. House Sparrows (Passer domesticus) are small passerines from Europe that have been successfully introduced to many parts of the world, and thus may be expected to exhibit high phenotypic flexibility in metabolic rate. Mass specific Resting Metabolic Rate (RMR) and Basal Metabolic Rate (BMR) were significantly higher in winter compared with summer, although there was no significant difference between body mass in summer and winter. A similar, narrow thermal neutral zone (25–28 °C) was observed in both seasons. Winter elevation of metabolic rate in House Sparrows was presumably related to metabolic or morphological adjustments to meet the extra energy demands of cold winters. Overall, House Sparrows showed seasonal metabolic acclimatization similar to other temperate wintering passerines. The improved cold tolerance was associated with a significant increase in VO₂ in winter relative to summer. In addition, some summer birds died at 5 °C, whereas winter birds did not, further showing seasonal variation in cold tolerance. The increase in BMR of 120% in winter, compared to summer, is by far the highest recorded seasonal change so far in birds.     

Gut morphology and morphometry in the epauletted Wahlberg's fruit bat (Epomophorus wahlbergi, Sundevall, 1846)

The morphological adaptations of the fruit bat small intestine to which the high functional efficiency could be related and the possible landmarks delineating the various parts of the gut were examined. The stomach was the carnivorous type with large rugae spanning the entire luminal aspect down to the pyloric sphincter, which was reflected internally as a prominent fold. Externally, the intestine was a continuous tube uninterrupted by any structures. The cranial fifth of the small gut had long, branching and anastomosing villi, which caudally turned to finger-like discrete structures that became rather short and stumpy and diminished at the beginning of the colon. The colon had longitudinal folds that were macroscopically discernible from the mucosal aspect of the opened intestine and that continued into the rectum. The small gut formed 94% of the whole intestinal length, the colon and the rectum taking 4 and 2%, respectively. Ultrastructurally, the enterocyte showed a prominent brush border and the lateral membranes were modified into numerous tortuous interdigitating processes. Adjacent enterocytes were joined by these processes through desmosomes. The processes also participated in pinocytotic fluid uptake from the intercellular spaces with resultant numerous intracellular vacuoles of varied sizes. Solutes absorbed into the cells were probably first passed into the intercellular compartment to create a concentration gradient thus enhancing further absorption into the cell. We conclude that the uniquely elaborate ultrastructure of the enteric epithelium coupled with the vast microvillous surface areas reported elsewhere are partly responsible for the very high absorption rates reported in the fruit bat small intestine.     

Seasonal variation in food availability and relative importance of dietary items in the Gambian epauletted fruit bat (Epomophorus gambianus)

相似文献   

Seasonal effects on thermoregulatory responses of the Rock Kestrel, Falco rupicolis

Thermoregulatory responses are known to differ seasonally in endotherms and this is often dependent on the environment and region they are resident. Holarctic animals are exposed to severe winters and substantial seasonal variation in ambient temperature. In contrast, those in the Afrotropics have less severe winters, but greater variation in temperature, rainfall and net primary production. These environmental factors place different selection pressures on physiological responses in endotherms. In this study, metabolic rate (VO₂) and body temperature (T_b) were measured in captive bred Rock Kestrels (Falco rupicolus) from the Afrotropics after a period of summer and winter acclimatisation. Resting metabolic rate was significantly lower after the winter acclimatisation period than after the summer acclimatisation period, and there was a shift in the thermoneutral zone from 20–33 °C in summer to 15–30 °C in winter. However, no significant difference in basal metabolic rate between summer and winter was found. The results show that Rock Kestrels reduce energy expenditure at low ambient temperatures in winter as expected in an Afrotropical species.     

Seasonal effects on the thermoregulation of invasive rose-ringed parakeets (Psittacula krameri)

Invasive species are a major threat to global biodiversity. Rose-ringed parakeets Psittacula krameri are widely established outside their native range and are successful invaders in many countries, including South Africa. Physiological and behavioral responses to environmental conditions are considered to be major factors that influence the abundance and distribution of birds. As rose-ringed parakeets are able to tolerate wide varieties of climatic conditions as invaders, it is important to understand their physiological responses to these. This study examined the effects of seasonal changes in ambient temperatures (T_a) on metabolic rate and body temperature (T_b) of captive-bred rose-ringed parakeets. Resting metabolic rate at various T_a and basal metabolic rate were significantly lower in winter compared to summer, and the thermo-neutral zone was broader in winter than in summer. There was no significant difference in body mass (M_b) between seasons. These parakeets showed seasonal thermoregulatory responses that represented energy conservation as expected, rather than cold tolerance. They were relatively tolerant of low T_a and showed no hypothermia at 5 °C. Our results suggest that this species is physiologically and behaviorally equipped to cope with a range of climatic situations and this partly explains their global success as an invader species.     

Nitrogen and energy requirements of the short-tailed fruit bat (Carollia perspicillata): fruit bats are not nitrogen constrained

 Nitrogen (N) and energy (E) requirements were measured in adult Carollia perspicillata which were fed on four experimental diets. Bats ate 1.3–1.8 times their body mass ⋅ day^-1 and ingested 1339.5–1941.4 kJ ⋅ kg^-0.75 ⋅ day^-1. Despite a rapid transit time, dry matter digestibility and metabolizable E coefficient were high (83.3% and 82.4%, respectively), but true N digestibility was low (67.0%). Mass change was not correlated with E intake, indicating that bats adjusted their metabolic rate to maintain constant mass. Bats were able to maintain constant mass with digestible E intake as low as 1168.7 kJ ⋅ kg^-0.75 ⋅ day^-1 or 58.6 kJ ⋅ . Metabolic fecal N and endogenous urinary N losses were 0.87 mg N ⋅ g^-1 dry matter intake and 172.5 mg N ⋅ kg^-0.75 ⋅ day^-1, respectively, and bats required 442 mg N ⋅ kg^-0.75 ⋅ day^-1 (total nitrogen) or 292.8 mg N ⋅ kg^-0.75 ⋅ day^-1 (truly digestible nitrogen) for N balance. Based on E and N requirements and digestibilities, it was calculated that non-reproductive fruit bats were able to meet their N requirements without resorting to folivory and without over-ingesting energy. It was demonstrated that low metabolic fecal requirements allowed bats to survive on low-N diets. Accepted: 23 June 1996     

Seasonal and geographic variation in thermal biology of the lizard Microlophus atacamensis (Squamata: Tropiduridae)

1.

We studied physiological thermal adaptation in the lizard Microlophus atacamensis along a latitudinal range.     

Seasonal trends in body mass, food intake and resting metabolic rate, and induction of metabolic depression in arctic foxes (Alopex lagopus) at Svalbard

 Post-absorptive resting metabolic rates (RMRs), body mass and ad libitum food intake were recorded on an annual cycle in captive arctic foxes (Alopex lagopus) at Svalbard. During the light season in May and in the dark period in November, RMR during starvation and subsequent re-feeding were also measured. In contrast to earlier findings, the present study indicated a seasonal trend in post-absorptive RMR (in W · kg⁻¹ and W · kg^−0.75). The values in the light summer were 15% and 11% higher than the values in the dark winter, suggesting a physiological adaptation aiding energy conservation during winter in arctic foxes. Body mass and ad libitum food intake varied inversely through the year. A significant reduction in RMR (in W and W · kg^−0.75) with starvation (metabolic depression) was recorded both in May and November, indicating an adaptation to starvation in arctic foxes. The lack of metabolic depression during a period of starvation that was concomitant with extremely cold ambient temperatures in November 1994 indicates that metabolic responses to starvation may be masked by thermoregulatory needs. At very low ambient temperatures, arctic foxes may require increased heat production which cannot be achieved via below-average rates of metabolism. Accepted: 7 June 1999     

Effects of summer- and winter-like acclimation on the thermoregulatory behavior of fed and fasted desert hamsters, Phodopus roborovskii

1.

Thermoregulatory behavior of fed and fasted desert hamsters (Phodopus roborovskii) acclimated to summer- [16 light (L):8 dark (D), ambient temperature (T_a)=26.5 °C] and winter-like (8L:16D, T_a=10 °C) conditions was studied. Body temperature (T_b), selected temperature and activity were measured in hamsters placed in a thermal gradient system for 48 h.     

Seasonal variability in feeding behaviour, metabolic rates and carbon and nitrogen balances in the Sydney oyster, Saccostrea glomerata (Gould)

To establish if nutrients limit the growth of bivalves requires information not only on the quality of food available, but also the animals' feeding behaviour and endogenous metabolic demands. We hypothesized that growth of the Sydney rock oyster (Saccostrea glomerata) would vary in response to seasonal changes in food quality rather than quantity. We also predicted that the oysters would show feeding preferences for nitrogen over carbon, and this behaviour would result in carbon/nitrogen (C/N) ratios for ingested and absorbed matter that would be lower than the C/N of both the seston and the oysters' estimated metabolic maintenance requirements. The experiments were done in two phases under natural conditions. In phase 1, feeding behaviour was assessed on a single occasion and the results used to pose hypotheses for testing in phase 2, which included measurements made on three occasions encompassing autumn, winter and spring conditions. Growth rates varied with changes in ambient food quality and not with the concentration of total suspended matter. Feeding behaviour responded to food quality and, in most cases, resulted in nitrogen enrichment. For example, when nitrogen was potentially limiting to growth and/or maintenance, due to high food C/N (July) or high nitrogen demand (March), pre-ingestive selection ensured nitrogen enrichment of ingested matter and C/N ratios of ingested matter which were below the maintenance requirement. However, in November, when endogenous demands indicated an increased requirement for carbon, feeding behaviour resulted in carbon enrichment, an increase in carbon conversion efficiency, and ingested C/N ratios greater than the maintenance requirement. The results support the assertion of variable feeding physiology in oysters, responsive to both exogenous (seasonal differences in carbon and nitrogen availability) and endogenous (cycles of reproduction and growth) factors.     

北京地区大足鼠耳蝠主要食物及其食性组成的季节变化

20 0 2年 5月至 2 0 0 3年 11月初 (冬眠期除外 ) ,约每两周一次 (每次调查持续 1- 2晚 )于北京房山霞云岭乡四合村蝙蝠洞 (115°5 9′N ,39°4 3′E)捕捉觅食后返洞的大足鼠耳蝠 (Myotisricketti) ,通过 2 8次野外调查收集了 342个粪便样品 ,分析了其食物组成的频率差异。北京地区大足鼠耳蝠主要捕食宽鳍 (Zaccoplaty pus) (在总样品中的频率为 6 0 2 % )、鲫鱼 (Carassiusauratus) (5 8% )和洛氏 (Phoxinuslagowskii) (2 3% )三种淡水鱼 ;还捕食至少 7个目的昆虫 ,分别为鞘翅目 (2 0 2 % )、鳞翅目 (12 6 % )、同翅目 (9 6 % )、蜉蝣目(4 1% )、半翅目 (5 6 % )、双翅目 (3 5 % )和膜翅目 (2 6 % )。两年中三种淡水鱼的总频率与昆虫的总频率差异显著 ;年内数据比较显示 ,鱼类和昆虫频率 2 0 0 2年差异不显著 ,2 0 0 3年差异显著。大足鼠耳蝠雨季和旱季食物种类基本无差异 ,但鱼类和昆虫在其食物组成中有年内波动 ,即大足鼠耳蝠旱季多以鱼类为食 ,雨季捕获昆虫的数量相对增加。据两年的研究结果 ,证实北京房山霞云岭大足鼠耳蝠的食物主要组成部分是三种鱼类 ,而宽鳍为主要食物成分的原因是其多在水体浅层活动而易被大足鼠耳蝠捕获。从能量收支平衡的角度推测大足鼠耳蝠在雨季捕食昆虫可能     

Seasonal variation in the temperature preference of Arctic charr (Salvelinus alpinus)

(1)

Seasonal variation in thermal preference of Arctic charr from a North Norwegian population (70°N) was studied in an electronic shuttlebox, which allowed the fish to control the water temperature by moving between two chambers. The fish were acclimated to 12 °C and a natural photoperiod before measurements. Fish were tested in autumn (September–October), winter (January–February), spring (April–May) and summer (June–August).     

Seasonal variation in metabolic rate of a medium-sized frugivore, the Knysna Turaco (Tauraco corythaix)

Many seasonal thermoregulation studies have been conducted on Holarctic birds that live in predictable, highly seasonal climates with severe winters. However, relatively few studies have been conducted on their southern hemisphere Afrotropical counterparts that encounter less predictable climates with milder winters. These latter birds are expected to conserve energy in winter by downregulating their metabolic rates. Therefore in this study, metabolic rate was measured during summer and winter in Knysna Turaco, Tauraco corythaix (Musophagiformes, Musophagidae) (c. 310 g), a non-passerine, in order to test whether there is energy conservation in winter. No overall significant differences in resting metabolic rates over a range of ambient temperatures were observed between winter and summer. However, whole-organism basal metabolic rates were 18.5% higher (p=0.005) in winter than in summer (210.83±15.97 vs. 186.70±10.52 O₂ h⁻¹). Knysna Turacos had broad thermoneutral zones ranging from 20 to 28 °C in winter and 10 to 30 °C in summer. These results suggest that Knysna Turacos show seasonal thermoregulatory responses that represent cold defense rather than energy conservation, which is contrary to what was expected.     

Seasonal variation of thermoregulatory behaviour in the Hippopotamus (Hippopotamus amphibius)

The hippopotamus (Hippopotamus amphibius) spends more than 12 h a day in the water. Hippos are often submitted to water temperatures that vary with the seasons. We hypothesize that this difference between cool and warm water temperatures leads to variations in behavioural thermoregulation. We recorded the exposure of hippos to sunshine at the beginning and at the end of the dry season. Our results show that (1) sunshine exposure lasted much longer in cool water and (2) sun-bathing occurred during the hottest hours. It is therefore likely that in cool water hippos were cold and expressed an original behaviour of search for heat.     

Torpor, thermal biology, and energetics in Australian long-eared bats (Nyctophilus)

Previous studies have suggested that Australian long-eared bats (Nyctophilus) differ from northern-hemisphere bats with respect to their thermal physiology and patterns of torpor. To determine whether this is a general trait of Australian bats, we characterised the temporal organisation of torpor and quantified metabolic rates and body temperatures of normothermic and torpid Australian bats (Nyctophilus geoffroyi, 7 g and N. gouldi, 10 g) over a range of air temperatures and in different seasons. The basal metabolic rate of normothermic bats was 1.36 ± 0.17 ml g⁻¹ h⁻¹ (N. geoffroyi) and 1.22 ± 0.13 ml g⁻¹ h⁻¹ (N. gouldi), about 65% of that predicted by allometric equations, and the corresponding body temperature was about 36 °C. Below an air temperature of about 25 °C bats usually remained normothermic for only brief periods and typically entered torpor. Arousal from torpor usually occurred shortly after the beginning of the dark phase and torpor re-entry occurred almost always during the dark phase after normothermic periods of only 111 ± 48 min (N. geoffroyi) and 115 ± 66 min (N. gouldi). At air temperatures below 10 °C, bats remained torpid for more than 1 day. Bats that were measured overnight had steady-state torpor metabolic rates representing only 2.7% (N. geoffroyi) and 4.2% (N. gouldi) of the basal metabolic rate, and their body temperatures fell to minima of 1.4 and 2.3 °C, respectively. In contrast, bats measured entirely during the day, as in previous studies, had torpor metabolic rates that were up to ten times higher than those measured overnight. The steady-state torpor metabolic rate of thermoconforming torpid bats showed an exponential relationship with body temperature (r ² = 0.94), suggesting that temperature effects are important for reduction of metabolic rate below basal levels. However, the 75% reduction of metabolic rate between basal metabolic rate and torpor metabolic rate at a body temperature of 29.3 °C suggests that metabolic inhibition also plays an important role. Torpor metabolic rate showed little or no seasonal change. Our study suggests that Australian Nyctophilus bats have a low basal metabolic rate and that their patterns of torpor are similar to those measured in bats from the northern hemisphere. The low basal metabolic rate and the high proclivity of these bats for using torpor suggest that they are constrained by limited energy availability and that heterothermy plays a key role in their natural biology. Accepted: 22 November 1999     

Diurnal, seasonal and sex variations in rectal temperature of African giant rats (Cricetomys gambianus, Waterhouse)

(1)

Rectal temperature (T_r) was measured in captive African giant rats (Cricetomys gambianus, Waterhouse), live-trapped in the Savannah during the harmattan, hot-dry and rainy seasons with the aim of determining diurnal, seasonal and sex patterns.

(2)

Mean (±SEM) T_r in the morning (37.16±0.04 °C) was lower (P<0.001) than the afternoon (37.49±0.03 °C) and evening (37.66±0.03 °C). There was no significant difference (P>0.05) between afternoon and evening T_r during the harmattan and rainy seasons, but the difference was significant (P<0.001) during the hot-dry season. Overall T_r was higher (P<0.001) during the hot-dry (38.03±0.03 °C) than harmattan (37.17±0.03 °C) and rainy (37.21±0.03 °C) seasons. T_r of bucks was lower than that of does (P<0.0001) during the harmattan and rainy seasons, but sex difference during the hot-dry season was not significant (P>0.05).

(3)

Base-line T_r values for the African giant rats are shown for the first time. Season, time of day and sex influence fluctuations in T_rs of African giant rats, and should be considered during diagnostic and clinical evaluations.