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.     

Seasonal variations in metabolism and thermoregulation in the striped hamster (Cricetulus barabensis)

(1)

Metabolic rate (MR), thermal neutral zone (TNZ), body temperature (T_b), and thermal conductance were measured in striped hamsters (Cricetulus barabensis) that were live-trapped in winter and summer.     

黑线仓鼠繁殖输出与基础代谢率的关系

为了解黑线仓鼠繁殖输出与基础代谢率(BMR)的关系,阐明最大持续能量收支(SusMR)的限制水平, 揭示哺乳期能量收支对策,本文测定了哺乳期黑线仓鼠的体重、摄食量、BMR 和身体组成,以及哺乳期的胎仔数、胎仔重和泌乳能量支出(MEO)。结果显示,黑线仓鼠哺乳期体重降低了15.0 ± 0.8% , 摄食量显著增加, 哺乳高峰期平均摄食量为13.9 ± 0.3 g /d, 摄入能为222.1 ± 5.3 kJ/ d, 比哺乳初期增加121% , 比对照组高288% ;哺乳高峰期MEO 为62.4 ± 2.3 kJ/ d, 哺乳末期BMR 为49.7 ± 1.1 kJ/ d; 断乳时平均胎仔数4.7 ± 0.2、窝胎仔重50.5 ±1.6 g; 哺乳末期BMR 比对照组增加48% ,BMR 与消化系统各器官的相关性高于对照组; BMR 与胎仔数、胎仔重、乳腺重量和MEO 显著正相关。结果表明:初次繁殖的黑线仓鼠哺乳期SusMR 限制为4.47 ×BMR, 在自身维持和繁殖输出之间采取了“权衡分配”的原则,通过体重降低以减少BMR 的增加幅度, 从而有利于繁殖输出。     

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

(1)

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.     

繁殖经历对黑线仓鼠哺乳期能量收支的影响

为探讨繁殖经历与哺乳期最大持续能量收支的关系,对连续4 次繁殖的黑线仓鼠哺乳期的能量收支情况进行了测定。结果显示:1)不同繁殖组哺乳高峰期的摄食量、泌乳能量支出(MEO)、胎仔数和胎仔重差异不显著,静止代谢率(RMR)、非颤抖性产热(NST)、褐色脂肪组织(BAT)线粒体细胞色素c 氧化酶(COX)活性、血清甲状腺激素(T3 、T4 )和催乳素水平也无明显变化;2)摄食量与MEO、胎仔重和RMR 呈显著正相关。结果表明,不同繁殖经历的黑线仓鼠主要通过降低产热和增加能量摄入来满足哺乳高峰期的能量需求;哺乳期最大持续代谢率(SusMR)可能受乳腺组织泌乳能力的限制,与“外周限制假说” 的预测一致,不支持“中心限制假说”;SusMR 限制因素和哺乳期能量收支策略可能与繁殖经历无关。     

环境温度和繁殖经历对黑线仓鼠哺乳期能量收支的影响

为探讨环境温度和繁殖经历对黑线仓鼠哺乳期能量收支的影响,将连续3次繁殖的黑线仓鼠暴露于温度梯度降低的条件下(30—0℃,1℃/4d),使初次、第2和3次繁殖的动物分别暴露于30—20℃、20—10℃、10—0C℃,测定了哺乳期能量收支。与初次繁殖的动物相比,第3次繁殖组动物的摄食量显著增加,静止代谢率、非颤抖性产热、褐色脂肪组织细胞色素c氧化酶(COX)活性和血清T3水平显著增加,而断乳时胎仔重显著降低。结果表明:(1)低温下繁殖的黑线仓鼠处于负能量平衡,在自身维持和哺育后代的能量分配之间存在权衡,低温下产热增加,繁殖输出减少;(2)黑线仓鼠可能感知环境温度的变化,在连续降低温度的条件下降低繁殖投资,符合"季节性投资假说"的预测。     

食物限制对黑线仓鼠免疫功能的影响

温带地区小型哺乳动物经常面临着食物资源的波动。食物对动物的免疫功能具有重要影响。将19只成年雄性黑线仓鼠(Cricetulus barabensis)随机分为自由取食组(n=9)和限食组(n=10)。注射植物血球凝集素(PHA)来测定细胞介导的免疫反应,用匙孔血蓝蛋白(KLH)免疫动物,然后测定抗KLH抗体的浓度以反映其体液免疫功能。旨在检验食物限制是否会抑制黑线仓鼠的细胞免疫和体液免疫功能。结果发现,与对照组相比,限食组黑线仓鼠具有较低的体重、体脂、脾脏鲜重、血清瘦素水平、免疫球蛋白Ig G和Ig M浓度。而限食对胸腺鲜重、白细胞数、皮质酮水平以及PHA反应没有显著影响。结果表明黑线仓鼠免疫系统的不同成分对限食反应存在差异,在食物资源短缺时,黑线仓鼠防御细胞外病原体的能力降低,从而导致生存能力的下降。     

食物限制对黑线仓鼠能量代谢和产热的影响

为阐明动物应对食物短缺的能量学对策与其自身的代谢水平的关系,测定了不同限食程度下黑线仓鼠的体重、基础代谢率和非颤抖性产热。结果发现,限食使基础代谢率、非颤抖性产热、褐色脂肪组织细胞色素c氧化酶活性降低。90% 限食驯化4 周后,存活率为80% ,60% 限食驯化4 周后,存活率为30% 。低温驯化使黑线仓鼠基础代谢率和非颤抖性产热显著增加,使80% 限食动物的体重和存活率显著降低。高基础代谢率组的摄食量比低基础代谢率组多23.8% ,80% 限食后两组体重降低的幅度和存活率差异不显著。结果表明:高水平的代谢率使黑线仓鼠对食物资源短缺的敏感性增加;支持“代谢率转换假说”,符合“具有储食习性的动物对食物短缺的生理耐受性较低” 的预测。     

被毛在黑线仓鼠能量代谢、产热和体温调节中的作用

为阐明小型哺乳动物被毛的季节性变化及其在能量代谢和体温调节中的作用,测定了季节性驯化,以及不同光周期和温度驯化的黑线仓鼠的被毛重量、体温和能量收支。结果显示: (1)冬季黑线仓鼠的被毛重量和产热显著高于夏季;(2)短光照(8L∶16D)和低温(5℃ ) 对被毛生长的影响不显著; (3)与室温组(21℃ )相比,低温组(5℃ )摄入能、基础代谢率(BMR)、非颤抖性产热(NST) 、褐色脂肪组织细胞色素c 氧化酶活性和热传导率显著增加,而暖温组(30℃ )显著降低; (4)室温和低温下,剃毛导致摄入能、BMR、NST 和热传导率显著增加;结果表明:被毛的作用与环境温度有关,低温下被毛降低了能量需求,增强了动物应对低温环境的适应能力;被毛的适应性变化是独居的野生小型哺乳动物应对环境温度季节性波动的主要适应策略之一,在其能量代谢和体温调节中具有重要作用和意义。     

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.     

Seasonal adjustments in body mass and thermogenesis in Mongolian gerbils (<Emphasis Type="Italic">Meriones unguiculatus</Emphasis>): the roles of short photoperiod and cold

Seasonal adjustments in body mass and thermogenesis are important for the survival of small mammals during acclimatization in the temperate zone. To determine the contributions of short photoperiod and cold temperatures to seasonal changes in thermogenesis and body mass in Mongolian gerbils (Meriones unguiculatus), body mass, basal metabolic rate (BMR), nonshivering thermogenesis (NST), energy intake and energy digestibility were determined in seasonally acclimatized and laboratory acclimated animals. Body mass showed significant seasonal changes and decreased to a minimum in winter. Both BMR and NST increased in winter, and these changes were mimicked by exposing animals to short photoperiod or cold temperatures in the animal house. Digestible energy intake also increased significantly in winter, and also during exposure of housed animals to both short photoperiod and cold. These results suggest that Mongolian gerbils overcome winter thermoregulatory challenges by increasing energy intake and thermogenesis, and decreasing body mass to reduce total energy requirements. Short photoperiod and cold can serve as effective environmental cues during seasonal acclimatization.     

Regulation of body weight and thermogenesis in seasonally acclimatized Brandt's voles (Microtus brandti)

Seasonal changes in an animal's morphology, physiology, and behavior are considered to be an adaptive strategy for survival and reproductive success. In the present study, we examined body weight and several behavioral, physiological, hormonal, and biochemical markers in seasonally acclimatized Brandt's voles (Microtus brandti) to test our hypothesis that Brandt's voles can decrease energy intake associated with decrease in body weight, body fat content, serum leptin level, and increasing thermogenesis in winter conditions. We found that the body weight of Brandt's voles was lowest in winter (December to February) and highest in spring and early summer (May to June). This seasonal variation in body weight was associated with changes in other markers examined. For example, the winter decrease in body weight was accompanied by increased energy intake and enhanced nonshivering thermogenesis (NST) as well as by decreased body fat mass and reduced levels of circulating leptin. Further, circulating levels of leptin were positively correlated with body weight and body fat mass, and negatively correlated with energy intake and uncoupling protein 1 contents. Together, these data do not support our hypothesis and suggest that leptin may be involved in this process and serve as a starvation signal in Brandt's voles.     

东北地区黑线仓鼠的代谢产热特征及其体温调节

为探讨寒冷地区黑线仓鼠 (Cricetulusbarabensis)的代谢产热特征及体温调节 ,本文采用封闭式流体压力呼吸仪对其代谢率、热传导和体温等热生物学指标进行了测定。结果显示 :在环境温度为 5～ 35℃的范围内 ,黑线仓鼠的体温基本维持恒定 ,平均体温为 36 33± 0 2 3℃ ;热中性区为 2 5～ 32 5℃ ;基础代谢率为 3 4 9±0 36mlO2 / (g·h) ;环境温度 (Ta)在 5～ 2 5℃范围内 ,代谢率 (MR)与Ta 呈负相关 ,回归方程为 :MR [mlO2 / (g·h) ]=9 6 0 - 0 2 2Ta (℃ ) ,在此范围内 ,黑线仓鼠的热传导率 (C)最低 ,平均为 0 2 8± 0 0 1mlO2 /(g·h·℃ ) ;代谢预期比和热传导预期比 (F值 )为 1 6 8。黑线仓鼠的基本热生物学特征为 :较高的BMR和热传导率 ,相对较低的体温和较宽的热中性区。这些特征可能限制了其在极端寒冷和干旱环境中的分布和生存.     

Seasonal regulations of energetics, serum concentrations of leptin, and uncoupling protein 1 content of brown adipose tissue in root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau

Survival of small mammals in winter requires proper adjustments in physiology, behavior and morphology. The present study was designed to examine the changes in serum leptin concentration and the molecular basis of thermogenesis in seasonally acclimatized root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau. In January root voles had lower body mass and body fat mass coupled with higher nonshivering thermogenesis (NST) capacity. Consistently, cytochrome c oxidase activity and mitochondrial uncoupling protein-1 (UCP1) protein contents in brown adipose tissues were higher in January as compared to that in July. Circulating level of serum leptin was significantly lower in winter and higher in July. Correlation analysis showed that serum leptin levels were positively related with body mass and body fat mass while negatively correlated with UCP1 protein contents. Together, these data provided further evidence for our previous findings that root voles from the Qinghai-Tibetan plateau mainly depend on higher NST coupled with lower body mass to enhance winter survival. Further, fat deposition was significantly mobilized in cold winter and leptin was potentially involved in the regulation of body mass and thermogenesis in root voles. Serum leptin might act as a starvation signal in winter and satiety signal in summer.     

EP-1不育剂对内蒙古沙地黑线仓鼠种群结构与繁殖的影响

2003年在内蒙古锡林郭勒盟浑善达克沙地进行了EP-1不育剂控制黑线仓鼠的野外实验,分析新型EP系列不育剂对黑线仓鼠种群结构和繁殖的影响。采用逐月夹线调查方法,监测EP-1不育剂对沙地黑线仓鼠种群结构与数量动态的作用。结果表明,投药区与对照区相比,不育剂对黑线仓鼠的性别比例没有影响,对照区域投药区相比雄性比例没有差异。投药区黑线仓鼠种群幼鼠比例下降,比对照区相比幼鼠比例下降40%—60%,持续时间达4个月以上。春季一次性投放EP-1不育剂,可实现对沙地黑线仓鼠整个繁殖季节的繁殖控制。此外,EP-1不育剂对沙地鼠类种群年龄结构与数量的作用成效,随着时间的推移逐渐下降,这可能跟沙地鼠类具有扩散迁移习性有关。     

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.     

不同繁殖状态雌性黑线仓鼠对植物血凝素的反应模式

由植物血凝素（Phytohemagglutinin,ＰＨＡ） 诱导产生的肿胀反应是生态免疫学中被广泛使用的免疫学参数,通过注射部位的肿胀程度大体上可反映细胞介导的免疫和天然免疫的综合变化情况。为探讨小型哺乳动物不同繁殖状态对ＰＨＡ 的反应模式,以非繁殖期、妊娠期、哺乳期和断乳期的雌性黑线仓鼠为研究对象,测定了注射ＰＨＡ 和生理盐水前（０ ｈ）及注射后６ ｈ、１２ ｈ 和２４ ｈ 注射部位皮肤组织的增厚程度。结果显示：（１）黑线仓鼠对ＰＨＡ 的反应有两种模式：非繁殖期、妊娠期和断乳期对ＰＨＡ 的反应模式相似,都在注射后６ ｈ 最高,１２ ｈ 和２４ ｈ 后逐渐下降;哺乳期对ＰＨＡ 的反应在注射后６ ｈ、１２ ｈ 和２４ ｈ 接近,彼此间的差异均不显著。（２）哺乳期黑线仓鼠的ＰＨＡ 反应高峰值有下降趋势,但与非繁殖期、妊娠期和断乳期高峰值之间的差异不显著。结果表明,黑线仓鼠在哺乳期对ＰＨＡ 的反应模式不同于其他繁殖阶段,且反应的高峰值被延迟,这对其存活可能有害,但有助于繁殖进程的延续和后代的生长发育。     

北小麝鼩的代谢产热和体温调节特征

为探讨食虫目小型哺乳动物的代谢产热和体温调节特征,本文采用封闭式流体压力呼吸仪测定了北小麝鼩在环境温度5 ～ 30℃下的静止代谢率(RMR),结果显示:在环境温度(Ta)为17 5 ～25℃ 的范围内,北小麝鼩的体温基本维持恒定,平均体温为36.55 ± 0.38℃ ;热中性区(TNZ) 为20 ～ 25℃ ;基础代谢率BMR 为5.46 ±0.23 (mLO₂ /g· h),其中环境温度在25℃ 时静止代谢率最低,为4.84 ± 0.39 (mLO₂ /g· h)。在5 ～ 25℃环境温度范围内,热传导值保持稳定;在此温度范围内,北小麝鼩的热传导率(C) 最低,平均为0.42 ± 0.01mLO₂ / (g·h·℃ )。总之,北小麝鼩的产热和体温调节特征为较高的BMR,中等的热传导率,较低的体温和较宽的热中性区。这些特征可能与该物种体型小、夜行性、主要以无脊椎动物为食等生活习性密切相关。     

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.     

Photoperiodic regulation in energy intake, thermogenesis and body mass in root voles (Microtus oeconomus)

The present study was designed to examine whether photoperiod alone was effective to induce seasonal regulations in physiology in root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau noted for its extreme cold environment. Root voles were randomly assigned into either long photoperiod (LD; 16L:8D) or short photoperiod (SD; 8L:16D) for 4 weeks at constant temperature (20 degrees C). At the end of acclimation, SD voles showed lower body mass and body fat coupled with higher energy intake than LD voles. SD greatly enhanced thermogenic capacities in root voles, as indicated by elevated basal metabolic rate (BMR), nonshivering thermogenesis (NST), mitochondrial protein content and uncoupling protein-1 (UCP1) content in brown adipose tissue (BAT). Although no variations in serum leptin levels were found between SD and LD voles, serum leptin levels were positively correlated with body mass and body fat mass, and negatively correlated with energy intake and UCP1 content in BAT, respectively. To summarize, SD alone is effective in inducing higher thermogenic capacities and energy intake coupled with lower body mass and body fat mass in root voles. Leptin is potentially involved in the photoperiod induced body mass regulation and thermogenesis in root voles.