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.     

Reproductive success and individual variation in feeding frequency of House Sparrows (Passer domesticus)

Parental care is assumed to be closely associated with individual differences in reproductive success. We investigated how feeding frequencies varied among parents and how this affected the subsequent reproductive success in insular populations of House Sparrows Passer domesticus in northern Norway. Female parents fed their offspring more than male parents did, and the feeding rates were positively related to the feeding rates of the partner. A positive relationship between feeding rates and bill depth was present in females. In males, the feeding rates were negatively related to total badge size and positively related to visible badge size, after the effect of other variables had been taken into account. A non-linear convex relationship between feeding frequency and hatch day was present in males, which could reflect either the seasonal change in weather conditions or the seasonal variation in food availability. For both sexes, feeding frequencies increased with increasing brood size, but at the same time the average feeding rate per nestling decreased with increased brood sizes. Finally, our results indicate that the amount of parental investment, measured as feeding rates during the nestling stage, may have a positive long-term influence both on the number of fledglings that recruit as well as the probability that fledglings survive until recruitment.     

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 acclimatization of metabolism in Eurasian tree sparrows (Passer montanus)

Acclimatization to winter conditions is an essential prerequisite for survival of small passerines of the northern temperate zone. Changes in photoperiod, ambient temperature and food availability trigger seasonal acclimatization in physiology and behavior of many birds. In the present study, seasonal adjustments in several physiological, hormonal, and biochemical markers were examined in wild-captured Eurasian tree sparrows (Passer montanus) from the Heilongjiang Province in China. In winter sparrows had higher body mass and basal metabolic rate (BMR). Consistently, the dry mass of liver, heart, gizzard, small intestine, large intestine and total digestive tract were higher in winter than in that in summer. The contents of mitochondrial protein in liver, and state-4 respiration and cytochrome c oxidase (COX) activity in liver and muscle increased significantly in winter. Circulating level of serum triiodothyronine (T₃) was significantly higher in winter than in summer. Together, these data suggest that tree sparrows mainly coped with cold by enhancing thermogenic capacities through increased organ masses and heightened activity of respiratory enzymes activities. The results support the view that prominent winter increases in BMR are manifestations of winter acclimatization in tree sparrows and that seasonal variation in metabolism in sparrows is similar to that in other small temperate-wintering birds.     

The role of the pineal gland in the photoperiodic control of bird song frequency and repertoire in the house sparrow, Passer domesticus

Temperate zone birds are highly seasonal in many aspects of their physiology. In mammals, but not in birds, the pineal gland is an important component regulating seasonal patterns of primary gonadal functions. Pineal melatonin in birds instead affects seasonal changes in brain song control structures, suggesting the pineal gland regulates seasonal song behavior. The present study tests the hypothesis that the pineal gland transduces photoperiodic information to the control of seasonal song behavior to synchronize this important behavior to the appropriate phenology. House sparrows, Passer domesticus, expressed a rich array of vocalizations ranging from calls to multisyllabic songs and motifs of songs that varied under a regimen of different photoperiodic conditions that were simulated at different times of year. Control (SHAM) birds exhibited increases in song behavior when they were experimentally transferred from short days, simulating winter, to equinoctial and long days, simulating summer, and decreased vocalization when they were transferred back to short days. When maintained in long days for longer periods, the birds became reproductively photorefractory as measured by the yellowing of the birds' bills; however, song behavior persisted in the SHAM birds, suggesting a dissociation of reproduction from the song functions. Pinealectomized (PINX) birds expressed larger, more rapid increases in daily vocal rate and song repertoire size than did the SHAM birds during the long summer days. These increases gradually declined upon the extension of the long days and did not respond to the transfer to short days as was observed in the SHAM birds, suggesting that the pineal gland conveys photoperiodic information to the vocal control system, which in turn regulates song behavior.     

Effects of short-term acclimation on thermoregulatory responses of the rock kestrel, Falco rupicolus

The effects of a short-term acclimation period on basal metabolic rate (BMR) and resting metabolic rate (RMR) were measured in captive-bred Rock Kestrels (Falco rupicolus). Birds were exposed to winter conditions (pre-acclimation) in a semi-natural environment before they were acclimated for a period of 3 weeks at a constant temperature of 25 °C and a constant light:dark cycle (12:12 h) (post-acclimation). After acclimation the kestrels showed changes in RMR, BMR and the width of the thermoneutral zone. There was inter- and intra-individual phenotypic plasticity in BMR and RMR both pre- and post-acclimation. However, more inter-individual variation was seen after acclimation. This study concurs with recent suggestions that phenotypic plasticity in BMR is prevalent in avian physiology, and thus a single-species-specific BMR value may not be representative. Furthermore, comparative avian studies of BMR need to account for phenotypic plasticity.     

Seasonal regulations of resting metabolic rate and thermogenesis in striped hamster (Cricetulus barabensis)

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Resting metabolic rate (RMR), nonshivering thermogenesis (NST) and mitochondria cytochrome c oxydase (COX) activity of brown adipose tissue (BAT), as well as weight of skin and fur were measured in striped hamsters (Cricetulus barabensis) that were live-trapped in the summer, autumn, winter and spring.     

Seasonal acclimation in resting metabolism of the skink, Mabuya brevicollis (Reptilia: Scincidae) from southwestern Saudi Arabia

The resting metabolic rate (RMR) of seasonally-acclimated Mabuya brevicollis of various body masses was determined at 20, 25, 30, 35 and 40 °C, using open-flow respirometry. RMR (ml g⁻¹ h⁻¹) decreased with increasing mass at each temperature. RMRs increaProd. Type: FTPsed as temperature increased. The highest and lowest Q₁₀ values were obtained for the temperature ranges 20–25 °C and 30–35 °C for the summer-acclimated lizards. The exponent of mass “b” in the metabolism-body mass relation ranged from 0.41 to 0.61. b values were lower in the autumn and winter-acclimated lizards than in spring and summer-acclimated lizards. Seasonal acclimation effects were evident at all temperatures (20–40 °C) for M. brevicollis. Winter-acclimated skinks had the lowest metabolic rates at different temperatures. The pattern of acclimation exhibited by M. brevicollis may represent a useful adaptation for lizards inhabiting subtropical deserts to promote activity during their active seasons.     

Thyroid hormones increase liver and muscle thermogenic capacity in the little buntings (Emberiza pusilla)

Thyroid hormones can increase energy expenditure and stimulate basal thermogenesis by lowering metabolic efficiency. In the present study, we examined the effects of thyroid hormones on basal heat production as well as on several physiological and biochemical measures indicative of thermogenic capacity to test our hypothesis that thyroid hormones stimulate increases in thermogenesis in little buntings. Little buntings that fed on thyroxine (T₄)–laced poultry food of 3 and 5 ppm concentrations showed increases in basal metabolic rate (BMR) during the 3-week acclimation. At the end, these buntings had lower body weights, higher levels of contents of mitochondrial protein, state 4 respiration and cytochrome c oxidase activity in liver and muscle, and higher concentrations of serum triiodothyronine (T₃) and T₄ compared to control buntings. These results support the argument that thyroid hormones play an important role in the regulation of thermogenic ability in buntings by stimulating mitochondrial respiration and enzyme activities associated with aerobic metabolism.     

Seasonal changes in body mass and thermogenesis in tree shrews (Tupaia belangeri): The roles of photoperiod and cold

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in small, wild mammals. To determine the contributions of photoperiod and cold on seasonal changes in energy metabolism and body mass, the resting metabolic rates (RMR), nonshivering thermogenesis (NST), energy intake and gut morphology of the tree shrews were determined in winter and summer and in laboratory acclimated animals. Body mass, RMR and NST increased in winter, and these changes were mimicked by exposing animals to short-day photoperiod or cold in the animal house. Energy intake and digested energy also increased significantly in winter, and also during exposure of housed animals to both short-day photoperiod and cold. The lengths and weights of small intestine increased in winter. These results indicated that Tupaia belangeri overcomes winter thermoregulatory challenges by increasing energy intake and thermogenesis, and adjusted gut morphology to balance the total energy requirements. Short-day photoperiod and cold can serve as environmental cues during seasonal acclimatization.     

Coevolution of Cryptosporidium tyzzeri and the house mouse (Mus musculus)

Two house mouse subspecies occur in Europe, eastern and northern Mus musculus musculus (Mmm) and western and southern Mus musculus domesticus (Mmd). A secondary hybrid zone occurs where their ranges meet, running from Scandinavia to the Black Sea. In this paper, we tested a hypothesis that the apicomplexan protozoan species Cryptosporidium tyzzeri has coevolved with the house mouse. More specifically, we assessed to what extent the evolution of this parasite mirrors divergence of the two subspecies. In order to test this hypothesis, we analysed sequence variation at five genes (ssrRNA, Cryptosporidium oocyst wall protein (COWP), thrombospondin-related adhesive protein of Cryptosporidium 1 (TRAP-C1), actin and gp60) in C. tyzzeri isolates from Mmd and Mmm sampled along a transect across the hybrid zone from the Czech Republic to Germany. Mmd samples were supplemented with mice from New Zealand. We found two distinct isolates of C. tyzzeri, each occurring exclusively in one of the mouse subspecies (C. tyzzeri-Mmm and C. tyzzeri-Mmd). In addition to genetic differentiation, oocysts of the C. tyzzeri-Mmd subtype (mean: 4.24 × 3.69 μm) were significantly smaller than oocysts of C. tyzzeri-Mmm (mean: 4.49 × 3.90 μm). Mmm and Mmd were susceptible to experimental infection with both C. tyzzeri subtypes; however, the subtypes were not infective for the rodent species Meriones unguiculatus, Mastomys coucha, Apodemus flavicollis or Cavia porcellus. Overall, our results support the hypothesis that C. tyzzeri is coevolving with Mmm and Mmd.     

Thermoregulatory responses in seasonally acclimatized captive Southern White-faced Scops-owls

Seasonal thermoregulatory responses that are associated with cold tolerance have been reported for many species that inhabit regions where winters are severe (e.g. Holarctic), but relatively few studies have focused on species from regions where the climate is more unpredictable (e.g. Southern Africa). In this study, metabolic rate (VO₂) and body temperature (T_b) was measured during summer and winter in captive Southern White-faced Scops-owl (Ptilopsis granti), to test for thermoregulatory responses representing energy conservation in winter. During winter the Southern White-faced Scops-owls increased resting metabolic rate (RMR) by 45% to regulate a set point T_b—a result similar to what had been shown in small passerines from the Holarctic region. Increased RMR and increased conductance at cold T_a's are suggestive of improved cold tolerance. Basal metabolic rate (BMR) was 0.60 mL O₂ g⁻¹ h⁻¹ and showed no seasonal flexibility. Thus, contrary to expectation, the Southern White-faced Scops-owls showed seasonal thermoregulatory responses that are unlikely to represent energy conservation which was expected for a medium-sized bird inhabiting unpredictable climates in Southern Africa.     

Cytochrome oxidase I sequences reveal possible cryptic diversity in the cosmopolitan symbiotic copepod Nesippus orientalis Heller, 1868 (Pandaridae: Siphonostomatoida) on elasmobranch hosts from the KwaZulu-Natal coast of South Africa

Over the past decade, numerous molecular phylogenetic studies uncovered cryptic diversity within the Copepoda, yet very few investigations focused on symbiotic copepods. Here we report mitochondrial DNA cytochrome oxidase I diversity in the cosmopolitan elasmobranch symbiont Nesippus orientalis off the KwaZulu-Natal coast of South Africa. Analysis of partial COI sequences of copepods sampled from a diversity of shark hosts, revealed the presence of two divergent clades. Diversity within the clades does not appear to be structured based on host species, host individual, geographic locality or time of sampling. However, divergence between the two clades seems to be related to host species. Phylogenetic analyses of representatives from the two clades, along with Nesippus spp., Caligus spp. and Lepeophtheirus spp. outgroups, further supports the distinction between the two clades. Future molecular phylogenetic investigations of widespread copepod symbionts most likely will reveal far greater levels of biodiversity than currently recognized.     

Seasonal effects on thermoregulatory abilities of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in KwaZulu-Natal,South Africa

Seasonal variations in ambient temperature (T_a) require changes in thermoregulatory responses of endotherms. These responses vary according to several factors including taxon and energy constraints. Despite a plethora of studies on chiropteran variations in thermoregulation, few have examined African species. In this study, we used the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi, body mass≈115 g) to determine how the thermoregulatory abilities of an Afrotropical chiropteran respond to seasonal changes in T_a. Mass specific Resting Metabolic Rates (RMR_Ta) and basal metabolic rate (BMR) were significantly higher in winter than in summer. Furthermore, winter body mass was significantly higher than summer body mass. A broad thermoneutral zone (TNZ) was observed in winter (15–35 °C) compared with summer (25–30 °C). This species exhibited heterothermy (rectal and core body temperature) during the photophase (bats' rest-phase) particularly at lower T_as and had a low tolerance of high T_as. Overall, there was a significant seasonal variation in the thermoregulatory abilities of E. wahlbergi. The relative paucity of data relating to the seasonal thermoregulatory abilities of Afrotropical bats suggest further work is needed for comparison and possible effects of climate change, particularly extreme hot days.     

Effects of photoperiod on energy budgets and thermogenesis in Mongolian gerbils (Meriones unguiculatus)

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To investigate the role of photoperiod on the regulation of energy budgets and thermogenesis in Mongolian gerbils, body mass (BM), body fat mass (BFM), basal metabolic rate (BMR), nonshivering thermogenesis (NST), gross energy intake (GEI), mitochondrial cytochrome c oxidase (COX) activity and uncoupling protein1 (UCP1) content of brown adipose tissue (BAT), and serum tri-iodothyronine (T₃), thyroxine (T₄) and leptin levels were measured.     

环境温度对白头鹎代谢产热和蒸发失水的影响

基础代谢率(BMR)是恒温动物维持正常生理机能的最小产热速率,是动物在清醒时维持身体各项基本功能所需的最小能量值。"能量需求"假设认为,鸟类短期BMR的调整可以通过改变内部器官的大小来适应能量需求。以白头鹎(Pycnonotus sinensis)为研究对象,分别在10℃和30℃的不同环境中适应4周后,测定了其BMR、蒸发失水(EWL)和内部器官(心、肝、肾、胃、小肠和整体消化道)的重量,同时分析了白头鹎内部器官的变化及与BMR的关系。驯化4周后,白头鹎暖温组(30℃)的体重有明显降低的趋势;经协方差校正体重后,低温组(10℃)单位体重BMR与整体BMR明显高于暖温组,同时两组间EWL表现出显著差异。协方差分析表明,低温组白头鹎的肝脏、肾脏、小肠及总消化道重量显著高于暖温组。低温引起白头鹎能量需求增加,内部器官发生相应改变,要求摄入更多的氧气以维持代谢平衡,导致散失更多的蒸发水。     

Comparative pollen morphology of Brachylena, Tarchananthus and two species of Tubulifloridites (Asteraceae) from the Eocene, Knysna Lignite of South Africa

Two fossil taxa Tubulifloridites antipodica and T. viteauensis recovered from the Eocene Knysna Lignite of South Africa were examined with scanning (SEM) and transmission electron microscopy (TEM). The details of their sculpturing and wall structure are similar to the same species of fossil dispersed pollen taxa recovered from southwestern Africa and South America. Fifteen species of the woody South African taxa, Brachylaena (9 species) and Tarchonanthus (6 species) were investigated with SEM and TEM. All of the taxa are tricolporate, spherical to slightly prolate, microechinate to echinate and have a bilayered columellate infrastructure, except B.ilicifolia, which has a single columellate infrastructural level with the “granularization” of the outer portion of the infrastructural layer or the inner layer of the tectum. There is a similar distribution of plesiomorphic and derived pollen characters in a number of aster subfamilies and tribes suggesting a similar evolutionary progression of pollen, and pollen wall character evolution was occurring synchronously in a variety of aster subfamilies during the middle Tertiary and that these unique pollen features may be important to the evolution and diversification of the Asteraceae.