KLH单独刺激不影响黑线仓鼠的静止代谢率

根据生活史理论,免疫功能与产热和繁殖等其他生理学功能类似,具有能量代价。然而,关于提高免疫能力的能量学代价的实验例证很少,且此类代价可能受所选择的免疫学参数和实验测定的影响。为探究提高小型哺乳动物免疫能力的能量学代价,以匙孔血蓝蛋白（Keyhole limpet haemocyanin,KLH）作为外源抗原刺激,在注射前（第0天）、注射后第5天和第10天,分别测定非繁殖期雌、雄性黑线仓鼠（Cricetulus barabensis）体重和静止代谢率（Resting metabolic rate, RMR）的变化,通过眼眶静脉丛采血技术和ELISA分析,分别测定第5天（抗IgM抗体）和第10天（抗IgG抗体）动物血清抗体含量的变化。结果显示：（1）雄鼠的体重高于雌鼠,雌、雄鼠实验组和对照组之间的体重均无差异且不随时间而增加;（2）无论雌鼠还是雄鼠,注射KLH组血清中抗IgM和抗IgG抗体的含量均高于注射生理盐水的对照组动物;（3）注射KLH前后,RMR既无性别差异,也无组间差异,同一组动物的RMR均不随取样时间点而变化（KLH注射后第5天和第10天）。结果表明,单一的KLH刺激激活了黑线仓鼠的体液免疫,但在能量不受限的情况下不影响体重和能量收支的变化。有两种可能的解释：黑线仓鼠增强的体液免疫可能以免疫系统内另一免疫组分活动的降低作为代价,或它对体液免疫应答具有构建能力,温和的免疫刺激不伴随额外的能量学代价。     

Energetic and developmental costs of mounting an immune response in greenfinches (<Emphasis Type="Italic">Carduelis chloris</Emphasis>)

It is assumed that there is a trade-off between the costs allocated to mounting an immune defence and those allocated to costly functions such as breeding and moulting. The physiological basis for this is that mounting an immune response to pathogen challenge has energetic and/or nutrient costs which may interfere with metabolic processes of the challenged individual. If the energetic costs of mounting an immune response are not too high, animals may face such costs by increasing their acquisition of food energy, suggesting that limited nutrients may be responsible for the costs of immune defence. We assessed the energetic and developmental costs of mounting an immune response in an experiment in captivity with first-year greenfinches (Carduelis chloris) challenged with sheep red blood cells and Brucella abortus. Antibody production against both antigens increased the daily energy expenditure (4.7%) of immune-challenged birds relative to control birds, although the difference was non-significant. We estimated that the maximum effect size supported by the data would be 9.9% higher in immune-challenged birds relative to control birds. We plucked the two outermost rectrices of each bird to assess the effects of the immune challenge on growth of the regenerated feathers. The immune challenge had no significant effect on the length of the regenerated rectrices. However, these feathers were more asymmetric in length in immune-challenged birds than in control birds. Although first-year male greenfinches paid a relatively low energetic cost when mounting an immune response, we suggest that immune-challenged individuals may have paid some costs over the long term based on the increased fluctuating asymmetry in the developing feathers.     

Humoral immune response suppresses reproductive physiology in male Brandt's voles (Lasiopodomys brandtii)

In order to evaluate the potential costs of humoral immune response, which is important for survival in small wild mammals, we studied the physiological function of adult male Brandt's voles (Lasiopodomys brandtii) challenged with human immunoglobulin G (IgG). Compared with controls, the immunochallenged voles showed significantly higher antibody levels 15 days after injection. Serum testosterone levels, and mass of testes and epididymides were lower in immunochallenged voles than in control animals. Body mass remained stable during the course of the experiment. Total and digestible energy intake showed a transient decrease following IgG injection, while resting metabolic rate (RMR) increased. Taken together, these data suggest a shift in metabolic priorities in response to immune challenge. Our results provide evidence that mounting a humoral immune response to an immunological challenge may have fitness costs in male Brandt's voles.     

Immune activity elevates energy expenditure of house sparrows: a link between direct and indirect costs?

The activation of an immune response is beneficial for organisms but may also have costs that affect fitness. Documented immune costs include those associated with acquisition of special nutrients, as well as immunopathology or autoimmunity. Here, we test whether an experimental induction of the immune system with a non-pathological stimulant can elevate energy turnover in passerine birds. We injected phytohaemagglutinin (PHA), a commonly used mitogen that activates the cell-mediated immune response, into the wing web of house sparrows, Passer domesticus. We then examined energetic costs resulting from this immune activity and related those costs to other physiological activities. We found that PHA injection significantly elevated resting metabolic rate (RMR) of challenged sparrows relative to saline controls. We calculated the total cost of this immune activity to be ca. 4.20 kJ per day (29% RMR), which is equivalent to the cost of production of half of an egg (8.23 kJ egg(-1)) in this species. We suggest that immune activity in wild passerines increases energy expenditure, which in turn may influence important life-history characteristics such as clutch size, timing of breeding or the scheduling of moult.     

长爪沙鼠对植物血凝素的反应及能量学代价的性别和季节差异

以野生长爪沙鼠为对象,通过外源注射植物血凝素(Phytohemagglutinin,PHA)和磷酸盐缓冲液,分别测定了夏季和冬季沙鼠注射前、注射24 h 和48 h 后体重和静止代谢率(Resting metabolic rate,RMR)的变化,以及48 h 后沙鼠足增重量和白细胞总数(White blood cell counts,WBCs)的变化,以检测沙鼠的免疫功能和能量代价的性别和季节差异。结果显示:1)注射PHA 能显著增加沙鼠足重和白细胞的总数,夏季白细胞的总数高
于冬季;2)冬季沙鼠体重高于夏季,雄鼠大于雌鼠,但PHA 处理对注射前后沙鼠的体重无影响;3)冬季RMR高于夏季,雄鼠大于雌鼠,但PHA 处理对沙鼠的RMR 无影响,PHA 处理对注射前后沙鼠的RMR 也无影响。这些结果表明,长爪沙鼠对PHA 的反应具有季节差异,但无性别差异,也没有发现明显的能量学代价,这可能与野外环境条件的大幅度波动(如环境温度和食物条件等)和沙鼠的繁殖状态有关。     

Energetic trade-offs between immunity and reproduction in male Japanese quail (Coturnix coturnix)

We investigated a postulated trade-off between reproduction and immune function by comparing the energetic costs of an immune response with phytohemagglutinin challenge (or injection) in castrated (low testosterone [T]) and intact (high T) Japanese Quail (Coturnix coturnix). Intact birds had higher resting metabolic rate (RMR) and significantly lower immune response than castrates. RMR of intact birds did not change in response to an immune challenge, suggesting that maintenance of reproductive tissues and associated high T is both immunosuppressive and energetically costly. Despite having a greater immune response than intact quail, castrates had a lower pre-challenge RMR than intact birds and paradoxically tended to decrease RMR during an immune challenge. This paradox may be because of pro-inflammatory cytokines that are released during immune responses. Cytokines promote energy conservation through malaise and soporific behaviors, possibly explaining the co-occurrence of a relatively strong immune response and a decrease in nocturnal RMR in castrates. The lower immune response in intact birds may not elicit as great a response of pro-inflammatory cytokines owing to an already elevated RMR from reproductive state, thus reducing any effect on RMR. The suppressed immune response and elevated RMR in intact birds may be because of T; however, we cannot separate the effects of T per se from the metabolic requirements of reproductive tissues.     

Costs of immune response in cold-stressed laboratory mice selected for high and low basal metabolism rates

To study whether mounting an immune response is energetically costly, mice from two lines divergently selected for high (H-BMR) and low (L-BMR) basal metabolic rate (BMR) were immunized with sheep red blood cells. Their energy budgets were then additionally burdened by sudden transfer from an ambient temperature of 23 degrees C to 5 degrees C. We found that the immune response of H-BMR mice was lower than that of L-BMR mice. However, the interaction between line affiliation and ambient temperature was not significant and cold exposure did not result in immunosuppression in either line. At 23 degrees C the animals of both lines seemed to cover the costs of immune response by increasing food consumption and digestive efficiency. This was not observed at 5 degrees C, so these costs must have been covered at the expense of other components of the energy budget. Cold exposure itself elicited a considerable increase in food intake and the mass of internal organs, which were also heavier in H-BMR than in L-BMR mice. However, irrespective of the temperature or line affiliation, immunized mice had smaller intestines, while cold-exposed immunized mice had smaller hearts. Furthermore, the observed larger mass of the liver and kidneys in immunized mice of both lines kept at 23 degrees C was not observed at 5 degrees C. Hence, immunization compromised upregulation of the function of metabolically active internal organs, essential for meeting the energetic demands of cold. We conclude that the difficulties with a straightforward demonstration of the energetic costs of immune responses in these animals stem from the extreme flexibility of their energy budgets.     

Is resting metabolic rate related to reproductive output in an orb-web spider,Argiope radon?

1. Resting metabolic rate (RMR) is a fundamental feature of animal biology that reflects the baseline level of energy expenditure. There are two main strategies that can address energy demands; animals can reallocate energy from maintenance by reducing RMR to meet energy demands (compensation model) or they can increase intake rate by increasing metabolic activities (performance model). 2. Orb-web spiders are sit-and-wait foragers that typically reside at the centre of their web waiting to intercept prey. Given their sedentary resource acquisition strategy, it is predicted that lower RMR is favoured to reduce self-maintenance energetic costs and to allow greater allocation to oogenesis (i.e., egg sac development). 3. In this study, we tested temporal variation in RMR of female Argiope radon (Araneae: Araneidae) spiders in response to mating status. Then we tested the degree to which between-individual variation in the parental RMR relates to reproductive output and spiderling early life-history traits. 4. Despite the notable between-individual variation, we found a temporal consistency of RMR in the female spiders at early adulthood. Mated females significantly reduced their RMR by around 35% compared to their unmated stage which supports compensation model. However, there was a significant correlation between female RMR and mass of the egg sac in these spiders which is an evidence for performance model. 5. Our findings suggest that energy management in this species is a complex phenomenon, both strategies are in effect simultaneously at within- and between-individual level shaping the individuals' phenotype.     

Energetic costs of parasitism in the Cape ground squirrel Xerus inauris

Parasites have been suggested to influence many aspects of host behaviour. Some of these effects may be mediated via their impact on host energy budgets. This impact may include effects on both energy intake and absorption as well as components of expenditure, including resting metabolic rate (RMR) and activity (e.g. grooming). Despite their potential importance, the energy costs of parasitism have seldom been directly quantified in a field setting. Here we pharmacologically treated female Cape ground squirrels (Xerus inauris) with anti-parasite drugs and measured the change in body composition, the daily energy expenditure (DEE) using doubly labelled water, the RMR by respirometry and the proportions of time spent looking for food, feeding, moving and grooming. Post-treatment animals gained an average 19g of fat or approximately 25kJd-1. DEE averaged 382kJd-1 prior to and 375kJd-1 post treatment (p>0.05). RMR averaged 174kJd-1 prior to and 217kJd-1 post treatment (p<0.009). Post-treatment animals spent less time looking for food and grooming, but more time on feeding. A primary impact of infection by parasites could be suppression of feeding behaviour and, hence, total available energy resources. The significant elevation of RMR after treatment was unexpected. One explanation might be that parasites produce metabolic by-products that suppress RMR. Overall, these findings suggest that impacts of parasites on host energy budgets are complex and are not easily explained by simple effects such as stimulation of a costly immune response. There is currently no broadly generalizable framework available for predicting the energetic consequences of parasitic infection.     

Does the strength of an immune response reflect its energetic cost?

The energetic cost of immune responses has been proposed to be an important basis for trade-offs between life-history traits, such as between survival and reproduction. A critical assumption of this hypothesis is that the magnitude of the energetic cost increases with the strength of an immune response, so that energy can be saved by partly suppressing a response. Here, we test this assumption experimentally. The immune system of great tits Parus major was experimentally activated by injecting different doses of phytohemagglutinin (PHA) in the wing web. We found the resting metabolic rate of immune challenged birds to increase by 5%. However, although great tits injected with a high dose had a stronger immune response, this was not paralleled by a higher metabolic rate. Thus, we found the energetic cost of the immune response to be relatively low and not dose-dependent. This suggests to us that the energetic cost of immune responses cannot form the basis for trade-offs between life-history traits.     

Immune challenge affects basal metabolic activity in wintering great tits

The costs of exploiting an organism's immune function are expected to form the basis of many life-history trade-offs. However, there has been debate about whether such costs can be paid in energetic and nutritional terms. We addressed this question in a study of wintering, free-living, male great tits by injecting them with a novel, non-pathogenic antigen (sheep red blood cells) and measuring the changes in their basal metabolic rates and various condition indices subsequent to immune challenge. The experiment showed that activation of the immune system altered the metabolic activity and profile of immune cells in birds during the week subsequent to antigen injection: individuals mounting an immune response had nearly 9% higher basal metabolic rates, 8% lower plasma albumin levels and 37% higher heterophile-to-lymphocyte ratios (leucocytic stress indices) than sham-injected control birds. They also lost nearly 3% (0.5 g) of their body mass subsequent to the immune challenge. Individuals that mounted stronger antibody responses lost more mass during the immune challenge. These results suggest that energetic expenditures to immune response may have a non-trivial impact upon an individual's condition.     

Energy and distribution in subterranean rodents: sympatry between two species of the genus Ctenomys

The low basal metabolic rate (BMR) observed in subterranean rodents, compared to that of surface-dwelling species of comparable size, has been proposed to be an adaptation to underground life. Two main hypotheses have been proposed to explain this finding, the cost of burrowing and the thermal stress. The former states that the low BMR is due to the high cost of extending the tunnel system whereas the other relates it to the possibility of overheating in burrows where evaporative and convective heat exchange are restricted. Additionally, both hypotheses related the energetics of subterranean rodent with spatial distribution. The genus Ctenomys is an excellent model to evaluate the cost of burrowing or thermal stress, since they are widely distributed, with members differing markedly in body mass. The aim of this study was to assess digging and basal energetics in two Ctenomys species that live in sympatry in a coastal grassland, but differ in their microspatial distribution by soil preference. We used the obtained energetic data to test both energy-distribution hypotheses. We measured BMR and digging metabolic rate (DMR) through open flow respirometry in two species exposed to soft and hard soils. In brief, DMR in Ctenomys talarum (100-170 g), as in Ctenomys australis (250-600 g), was unaffected by soil hardness. Within thermoneutral zone of each species, DMR/RMR quotient was lower in the smaller species. Our data did not support the thermal stress hypothesis, but the cost of burrowing hypothesis was not rejected. Other alternative hypotheses are proposed to explain the distribution of C. talarum and C. australis.     

Male mealworm beetles increase resting metabolic rate under terminal investment

Harmful parasite infestation can cause energetically costly behavioural and immunological responses, with the potential to reduce host fitness and survival. It has been hypothesized that the energetic costs of infection cause resting metabolic rate (RMR) to increase. Furthermore, under terminal investment theory, individuals exposed to pathogens should allocate resources to current reproduction when life expectancy is reduced, instead of concentrating resources on an immune defence. In this study, we activated the immune system of Tenebrio molitor males via insertion of nylon monofilament, conducted female preference tests to estimate attractiveness of male odours and assessed RMR and mortality. We found that attractiveness of males coincided with significant down‐regulation of their encapsulation response against a parasite‐like intruder. Activation of the immune system increased RMR only in males with heightened odour attractiveness and that later suffered higher mortality rates. The results suggest a link between high RMR and mortality and support terminal investment theory in T. molitor.     

The effects of reproductive state on digestive efficiency in three sympatric bat species of the same guild

The functional link between food as an energy source and metabolizable energy is the digestive tract. The digestive organs may change in size, structure, or retention time in response to energetic demands of the animal. Very efficient digestive tracts may be better at processing food but require higher energetic investments for maintenance even when post-absorptive. These costs influence the resting metabolic rate (RMR) that is defined as the energy necessary to fuel vital metabolic functions in a resting animal. In bats a trade-off between the necessity for a highly efficient digestive tract and moderate energetic maintenance costs may be particularly important. We hypothesized that low RMR coincides with low digestive efficiency (defined as apparent metabolizable energy coefficient (MEC)) and that phases of increased energetic demand are compensated for by increased digestive efficiency. We measured RMR and apparent MEC in the bats species Myotis nattereri, M. bechsteinii, and Plecotus auritus. In support of our hypothesis, M. nattereri has the lowest mass-specific RMR of the three species and the lowest apparent MEC. However, apparent MEC did not change during phases with differing energetic demands in any of the bat species, probably because bats operate at the limit of their sustainable energy demand.     

House sparrows offset the physiological trade‐off between immune response and feather growth by adjusting foraging behavior

Growing feathers and mounting immune responses are both energetically costly for birds. According to the life history trade‐off hypothesis, it has been posited that the costs of feather growth lead to temporal isolation between molt and other expensive activities, reproduction for example. In contrast to life cycle events, the need to mount an immune response can occur at any time, including during feather growth. Thus, we hypothesized that mounting an immune response during feather growth may divert energy and resources from feather growth and impair feather renewal. To test this hypothesis, we clipped or plucked the same feathers of male house sparrows Passer domesticus biblicus. In the clipped group (n = 16), the feathers were absent with no regrowth; in the plucked group (n = 14), feathers were absent and regrowth was initiated. We also had an intact control group of 15 sparrows. We then initiated an inflammatory immune response by subcutaneous injection over the left breast muscle of the birds with a lipopolysaccharide (LPS) and quantified behavioral and physiological responses. We predicted that sparrows with plucked feathers would incur the highest energetic costs while mounting an immune response, and would increase their foraging effort to offset this cost. We found no difference in body mass and resting metabolic rates among sparrows subjected to the different feather and immune treatments. However, we did find that while sparrows with plucked feathers increased foraging efficiency following the immune challenge by paying fewer but longer visits to the food tray, allowing them to maintain food consumption. Foraging efficiency in sparrows with clipped feathers was reduced. We also found that quality of newly grown feathers after the immune challenge was poorer in the plucked group, suggesting that mounting an immune response competes with feather growth for resources.     

Wheel-running activity and energy metabolism in relation to ambient temperature in mice selected for high wheel-running activity

Interrelationships between ambient temperature, activity, and energy metabolism were explored in mice that had been selectively bred for high spontaneous wheel-running activity and their random-bred controls. Animals were exposed to three different ambient temperatures (10, 20 and 30°C) and wheel-running activity and metabolic rate were measured simultaneously. Wheel-running activity was decreased at low ambient temperatures in all animals and was increased in selected animals compared to controls at 20 and 30°C. Resting metabolic rate (RMR) and daily energy expenditure (DEE) decreased with increasing ambient temperature. RMR did not differ between control and selected mice, but mass-specific DEE was increased in selected mice. The cost of activity (measured as the slope of the relationship between metabolic rate and running speed) was similar at all ambient temperatures and in control and selected mice. Heat generated by running apparently did not substitute for heat necessary for thermoregulation. The overall estimate of running costs was 1.2 kJ/km for control mice and selected mice.     

Energetics during hatchling dispersal of the olive ridley turtle Lepidochelys olivacea using doubly labeled water

Studies of metabolism are central to the understanding of the ecology, behavior, and evolution of reptiles. This study focuses on one phase of the sea turtle life cycle, hatchling dispersal, and gives insight into energetic constraints that dispersal imposes on hatchlings. Hatchling dispersal is an energetically expensive phase in the life cycle of the olive ridley turtle Lepidochelys olivacea. Field metabolic rates (FMRs), determined using the doubly labeled water (DLW) method, for L. olivacea hatchlings digging out of their nest chamber, crawling at the sand surface, and swimming were five, four, and seven times, respectively, the resting metabolic rate (RMR). The cost of swimming was 1.5 and 1.8 times the cost of the digging and crawling phases, respectively, and we estimated that if L. olivacea hatchlings swim at frenzy levels, they can rely on yolk reserves to supply energy for only 3-6 d once they reach the ocean. We compared our RMR and FMR values by establishing an interspecific RMR mass-scaling relationship for a wide range of species in the order Testudines and found a scaling exponent of 1.06. This study demonstrates the feasibility of using the DLW method to estimate energetic costs of free-living sea turtle hatchlings and emphasizes the need for metabolic studies in various life-history stages.     

Effect of dietary restriction on immune response of laboratory mice divergently selected for basal metabolic rate

To study whether dietary restriction (DR; 70% of ad lib. feeding)-elicited immunosuppression results from the trade-off between the costs of mounting an immune response and the metabolic costs of maintenance, we subjected mice from two divergent lines selected for high basal metabolic rate (H-BMR) and low BMR (L-BMR) to 4 wk of DR and then challenged them with keyhole limpet hemocyanin (KLH) antigen. Those line types differ genetically with respect to BMR and to the mass of metabolically expensive internal organs, which are larger in H-BMR mice. In mice of both line types, DR resulted in a significant reduction of body mass, an immune response, and the downsizing of spleen, lymph nodes, thymus, heart, and kidneys but not small intestines. DR resulted in a greater reduction of the spleen and lymph nodes in mice of the H-BMR line type, whereas the thymus was more affected in L-BMR line type. In contrast, immunization resulted in an increase of liver mass in DR mice of both line types. A comparison of the results of current and earlier studies on the same mouse line types suggests that metabolic trade-offs involving the costs of an immune response are more apparent when animals are forced to increase energy demands (e.g., by cold exposure) compared to when energy demands are decreased through DR. Our findings also suggest that divelrgent selection on BMR resulted in between-line-type differences in T-cell- and B-cell-mediated types of an immune response. More generally, our results indicate that production of a wide repertoire of antibodies is not correlated with high BMR.     

Effects of feeding and habitat on resting metabolic rates of the Pacific walrus

Arctic marine mammals live in a rapidly changing environment due to the amplified effects of global warming. Pacific walruses (Odobenus rosmarus divergens) have responded to declines in Arctic sea-ice extent by increasingly hauling out on land farther from their benthic foraging habitat. Energy models can be useful for better understanding the potential implications of changes in behavior on body condition and reproduction but require behavior-specific metabolic rates. Here we measured the resting metabolic rates (RMR) of three captive, adult female Pacific walruses through breath-by-breath respirometry when fed and fasted resting out of water (sitting and lying down) and while fed resting in water. RMR in and out of water were positively related with pretrial energy intake when not fasted and 25% higher than RMR when walruses were fasted and out of water. Overall, RMR was higher than previously estimated for this species. Fasting RMR out of water was only 25% lower than subsurface swimming metabolic rates suggestive of relatively efficient swimming in adult females. Our results identify the importance of considering feeding status and species-specific differences in affecting metabolic costs. Further research is needed to better understand potential energetic costs of thermoregulation at temperatures experienced by wild walruses.     

Energetic output of subadult polar bears (Ursus maritimus): resting, disturbance and locomotion.

1. Indirect calorimetry was used to determine metabolic rates in subadult polar bears at rest after human-controlled disturbance and at four rates of locomotion. 2. Disturbance factors that do not result in locomotion would only have a significant effect on energy expenditure if they occurred over an extended period of time. 3. Human disturbance resulting in locomotion would have a relatively high energetic cost to individual animals. 4. Polar bears may require a relatively high energetic output to initiate walking.