Minimal metabolism, summit metabolism and plasma thyroxine in rodents from different environments

Rodents were live-trapped in three environments (desert, intermediate and coastal) in Southern California, USA, chosen because of the taxonomic overlap of species. Upon capture, blood samples were taken and plasma thyroxine concentrations were measured. Four species (Dipodomys merriami, Perognathus fallax, Peromyscus eremicus and Peromyscus californicus) were returned to the laboratory for measurement of minimal and summit rates of metabolism. Heteromyid rodents had significantly lower plasma thyroxine concentrations (14-44 nmol l-1) than cricetid rodents (18-93 nmol l-1). Although there was significant habitat difference in plasma thyroxine levels, this influence was not constant between heteromyid and cricetid rodents. In most species, the desert individuals had the lowest plasma thyroxine concentration. Minimal metabolic rates were lower than expected in all four species, as well as in the tropical heteromyid Liomys salvini and summit metabolic rates were similarly reduced in all species. Upon capture there was considerable variation in plasma thyroxine concentration of different species (23-93 nmol l-1). However, following 10 weeks in captivity, the range and variability of plasma thyroxine levels in these species was considerably reduced (32-64 nmol l-1).     

Pressure resistance of aerobic metabolism in eels from different water environments

Eels from different locations were tested comparing their energetic capacities to migrate by studying muscle (red and white) aerobic metabolism. As the migratory activity corresponds to a lengthy swimming activity at depth, their pressure resistance was evaluated by considering fish response to compression, mitochondrial respiration measured under pressure (101 ATA) and cytochrome c oxidase after 3 days under pressure. The results show that only fish from two of the sites have the metabolic capacities to cope with the high pressure encountered during migration.     

Oxygen consumption and body temperature in yellow-bellied marmot populations from montane-mesic and lowland-xeric environments

Summary Yellow-bellied marmots characteristically live in montane-mesic environments, but in several areas in western North America, this species extended its range into lowland-xeric habitats. Body mass was significantly smaller in the lowland-xeric population from eastern Washington at 393 m than in the montane-mesic population from western Colorado at 2900 m. Oxygen consumption of marmots from montane-mesic and lowland-xeric environments was signiflcantly affected by ambient temperature (T_A) water regimen, population, and a population x water regimen x temperature interaction. Lowland-xeric animals had a higher metabolic rate at low T_As, but a lower metabolic rate at higher T_As than the montane-mesic aminals. Oxygen consumption was lower on a restricted-water regimen than on ad libitum water in both populations. Coefficients relating oxygen consumption to body mass were affected by T_A, water regimen, and population. These intraspecific coefficients are larger than the interspecific coefficients for all mammals. Body temperature (T_B) was affected significantly by T_A, water regimen, and population. T_A body mass, and a population x water regimen interaction significantly affected conductance. Conductance generally was higher in the lowland-xeric than in the montane-mesic marmots. Both populations increased conductance at high T_A, but the lowland-xeric population dissipated a much higher proportion of the heat by evaporative water loss (EWL) than did the montane-mesic population. Metabolic water production exceeded or equaled EWL at 5–20°C. Smaller body size, reduced metabolism at high T_A, and increased EWL at high T_A characterized the lowland-xeric population.Metabolic rates of yellow-bellied marmots were higher than predicted from body size during the reproductive season but decreased to 67% of that predicted from the Kleiber curve by late summer. Marmots minimize thermoregulatory costs by concentrating activity at times when the microclimate is favorable, by tolerating hyperthermia at high T_A in the field, and by having a conductance lower than that predicted from body size.Abbreviations DHC dry-heat conductance - EHL evaporative heat loss - EWL evaporative water loss - HP heat produced - T _A ambient temperature - T _n body temperature - M body mass     

Geographic range and body size in Neotropical marsupials

Aim Our aim is to investigate the relationship between body size and geographical range in Neotropical marsupials, considering the possible effects of latitude and phylogeny. Location Neotropical region. Methods Phylogenetic generalized least‐squares regression method (PGLS) is used to investigate the relationship between body size, geographical range, and latitude considering the phylogenetic relationship between species. Data for 22 species were compiled from the literature. Results The scattergram of body size vs. geographical range was triangular in shape. Body size and geographical range were positively correlated throughout the phylogeny. Latitude was not important to this relationship. Conclusions The polygonal relationship between geographical range and body size seems to be moulded by ecological and geographical constraints rather than by a common association with latitude.     

Thermal acclimation of metabolism and preferred body temperature in lizards

• 1.1.|The standard metabolic rates (SMRs) and preferred body temperatures (PBTs) of the tropical cordylid Cordylus jonesi and temperature lacertid Lacerta lilfordi were determined following acclimation to constant environmental temperatures of 20 and 30°C.
• 2.2.|Although after 5 weeks the SMRs of Cordylus jonesi and Lacerta lilfordi displayed partial compensations of 20.9 and 10.5%, respectively, their PBTs did not alter over this period. Therefore, acclimation does not maintain complete metabolic homeostasis during either the active or inactive phase of the lizard.
• 3.3.|Cordylus jonesi allowed to thermoregulate behaviourally at their PBT during activity possessed similar SMRs to control animals maintained continually at the same background temperatures, indicating that acclimation state in lizards is determined by the body temperatures experienced while at rest.
• 4.4.|The particular acclimatory problems of animals exhibiting behavioural homeothermy are discussed.

     

常温常压下蚯蚓不同体段再生体节和再生质量研究

将蚯蚓从不同位置切断,得到有头无尾、无头有尾、无头无尾3组19种类型的体段,在常温(15～18℃)常压下培养,观察和记录其再生体节数和再生质量.结果表明,切断位置不同,其再生体节和再生质量有明显的差异.切后都保留了心脏、生殖环、脑或只切除了脑,所剩体节数均在实验所用蚯蚓的体节数的1/2以上的蚯蚓体段,再生体节数明显,其它各体段组再生体节数不明显或无.在培养13～27 d内死亡的蚯蚓,其再生质量呈减小趋势;能存活到48 d之后的蚯蚓,在有头无尾、无头有尾体段组中,再生质量呈增加趋势,在无头无尾体段组中,再生质量呈下降趋势.     

Quantitative comparisons between the karyotypes of Australian marsupials from three different superfamilies

Relative DNA values and percent lengths of chromosome arms have been studied for six species of the super-family Dasyuroidea, five species of Phalangeroidea and four species of Perameloidea. By multiplying by relative DNA values all percent lengths have been expressed in the same units. Two species are said to share a chromosome if neither of the arms differs at the 5% level of probability. It is argued that if species share at least two two-armed chromosomes, this can be taken as evidence of relationship. A standard dasyurid karyotype has been defined and individual species of Dasyuridae show only small deviations from it. The nature and significance of the bi-modal distribution of chromosome numbers in marsupials is discussed.     

环境温度对爪鲵体温及能量代谢的影响

应用封闭式小动物能量代谢仪测定了爪鲵在6℃、10℃、15℃、20℃和25℃环境条件下的体温和能量代谢以及在极端环境中的耐受性,探讨环境温度对爪鲵体温及能量代谢的影响.结果表明:爪鲵体温与环境温度呈正相关,其直线回归方程为:Tb=0.6966 0.9518Ta,相关非常显著.爪鲵对极端环境温度的耐受力较弱,在32℃-35℃高温和-2℃到-6℃低温 环境中的致死体温(TbL50)分别为27.7℃±0.9165℃和2.85℃±0.1539℃.在环 境温度为6℃-25℃的范围内,爪鲵的能量代谢与环境温度呈指数回归相关,指数方程为MR=0 .7495e0.0408x,相关显著.其代谢水平随环境温度的升高而升高,不同于内热源动物的代谢特征,爪鲵的体温调节和能量代谢显示出外热源动物的特点     

Energy metabolism and body temperature of barn owls fasting in the cold

Energetic adaptation to fasting in the cold has been investigated in a nocturnal raptor, the barn owl (Tyto alba), during winter. Metabolic rate and body temperature (Tb) were monitored in captive birds, (1) after acute exposure to different ambient temperatures (Ta), and (2) during a prolonged fast in the cold (4 degrees C), to take into account the three characteristic phases of body fuel utilization that occur during a long-term but reversible fast. In postabsorptive birds, metabolic rate in the thermoneutral zone was 4. 1+/-0.1 W kg-1 and increased linearly below a lower critical temperature of 23 degrees C. Metabolic rate was 70% above basal at +4 degrees C Ta. Wet thermal conductance was 0.22 W kg-1 degrees C-1. During fasting in the cold, the mass-specific resting metabolic rate decreased by 16% during the first day (phase I) and remained constant thereafter. The amplitude of the daily rhythm in Tb was only moderately increased during phase II, with a slight lowering (0. 6 degrees C) in minimal diurnal Tb, but rose markedly in phase III with a larger drop (1.4 degrees C) in minimal diurnal Tb. Refeeding the birds ended phase III and reversed the observed changes. These results indicate that diurnal hypothermia may be used in long-term fasting barn owls and could be triggered by a threshold of body lipid depletion, according to the shift from lipid to protein fuel metabolism occurring at the phase II/phase III transition. The high cost of regulatory thermogenesis and the limited use of hypothermia during fasting may contribute to the high mortality of barn owls during winter.     

Renal anatomy in sparrows from different environments

The renal anatomy of three species of sparrows, two from mesic areas, the House Sparrow (Passer domesticus) and Song Sparrow (Melospiza melodia), and one salt marsh species, the Savannah Sparrow (Passerculus sandwichensis) was examined. Electron microscopy was used to describe the ultrastructure of the nephron. In addition, stereology was used to quantify the volumes of cortex, medulla, and major vasculature of the kidneys, and the volumes and surface areas occupied by individual nephron components. There appeared to be no differences in the ultrastructural anatomy of the nephrons among the sparrows. Proximal tubules contained both narrow and wide intercellular spaces filled with interdigitations of the basolateral membrane. The thin limbs of Henle contained very wide intercellular spaces which were absent in the thick limbs of Henle. The distal tubule cells contained short, apical microvilli and infoldings of the basolateral membrane. In cross section, the medullary cones of all birds display an outer ring of thick limbs of Henle which surround an inner ring of collecting ducts, which in turn surround a central core of thin limbs of Henle. The Savannah Sparrow has a significantly higher volume of medulla compared to the two more mesic species. Within the cortex, the Savannah Sparrow also has a significantly higher volume of proximal tubules but a significantly lower volume of distal tubules than the other species. Within the medulla, the Savannah Sparrow has a significantly higher volume and surface area of capillaries, and a significantly higher surface area of thick limbs of Henle and collecting ducts than the mesic species. These data suggest that the salt marsh Savannah Sparrow has the renal morphology necessary to produce a more highly concentrated urine than the mesic zone species.     

Deep body and surface temperature responses to hot and cold environments in the zebra finch

Global warming increasingly challenges thermoregulation in endothermic animals, particularly in hot and dry environments where low water availability and high temperature increase the risk of hyperthermia. In birds, un-feathered body parts such as the head and bill work as ‘thermal windows’, because heat flux is higher compared to more insulated body regions. We studied how such structures were used in different thermal environments, and if heat flux properties change with time in a given temperature. We acclimated zebra finches (Taeniopygia guttata) to two different ambient temperatures, ‘cold’ (5 °C) and ‘hot’ (35 °C), and measured the response in core body temperature using a thermometer, and head surface temperature using thermal imaging. Birds in the hot treatment had 10.3 °C higher head temperature than those in the cold treatment. Thermal acclimation also resulted in heat storage in the hot group: core body temperature was 1.1 °C higher in the 35 °C group compared to the 5 °C group. Hence, the thermal gradient from core to shell was 9.03 °C smaller in the hot treatment. Dry heat transfer rate from the head was significantly lower in the hot compared to the cold treatment after four weeks of thermal acclimation. This reflects constraints on changes to peripheral circulation and maximum body temperature. Heat dissipation capacity from the head region increased with acclimation time in the hot treatment, perhaps because angiogenesis was required to reach peak heat transfer rate. We have shown that zebra finches meet high environmental temperature by heat storage, which saves water and energy, and by peripheral vasodilation in the head, which facilitates dry heat loss. These responses will not exclude the need for evaporative cooling, but will lessen the amount of energy expend on body temperature reduction in hot environments.