Body Mass0 Research Articles

Ontogenetic scaling of foot musculoskeletal anatomy in elephants

This study quantifies the shape change in elephant manus and pes anatomy with increasing body mass, using computed tomographic scanning. Most manus and pes bones, and manus tendons, maintain their shape, or become more gracile, through ontogeny. Contrary to this, tendons of the pes become significantly more robust, suggesting functional adaptation to increasingly high loads. Ankle tendon cross-sectional area (CSA) scales the highest in the long digital extensor, proportional to body mass(1.08+/-0.21), significantly greater than the highest-scaling wrist tendon (extensor carpi ulnaris, body mass(0.69+/-0.09)). These patterns of shape change relate to the marked anatomical differences between the pillar-like manus and tripod-like pes, consistent with differences in fore- and hindlimb locomotor function. The cartilaginous predigits (prepollux and prehallux) of the manus and pes also become relatively more robust through ontogeny, and their pattern of shape change does not resemble that seen in any of the 10 metacarpals and metatarsals. Their CSAs scale above isometry proportional to body mass(0.73+/-0.09) and body mass(0.82+/-0.07) respectively. We infer a supportive function for these structures, preventing collapse of the foot pad during locomotion.

ONTOGENY OF THE FOOD-GATHERING SYSTEM IN ORDOVICIAN CRINOIDS

The growth of the food-gathering systems of Ordovician crinoids illustrates the solutions evolved to avoid or minimize problems of suspension feeding and maintenance. The column has low metabolic requirements and may even be self-sufficient; little or no food need be diverted from the crown to the column. The tissue that the food-gathering system supplies with food is all or mostly in the crown. The volume of tissue in the crown is isometric with its volume. Distal arm branches, ramules, or pinnules form throughout growth of most taxa. The number of arm branches is constant in hybocrinids and porocrinids. The length and number of plates in the food-gathering system show marked positive allometry relative to crown volume. Food grooves become wider in larger crinoids but growth rates vary greatly. Branch density declines in all species studied. The tubefoot spacing can be constant, increase, or decrease in larger crinoids. Food-gathering capacity is the number of food-catching tubefeet multiplied by the average food-groove width, and it is positively allometric in terms of crown volume. The food-gathering ratio (food-gathering capacity: crown volume) declines somewhat, remains the same, or increases slightly during growth. The food-gathering parameters are correlated with arm structure. Crinoids with pinnulate arms exhibit the highest food-gathering ratios, high values of tubefoot spacing and branch density, and narrow food grooves, and they catch small food particles with small and closely spaced tubefeet. The lowest food-gathering ratios are seen in crinoids with unbranched and nonpinnulate arms which possess low tubefoot spacings and branch densities and wide food grooves. On average these organisms ate larger food items collected by larger and more widely spaced tubefeet. Larger food-gathering ratios are associated with greater resistance to fluid flow through the arms and tubefeet. The allometry of the food-gathering systems of Ordovician crinoids suggests that their metabolic rates could be proportional to body mass0.75 as in many living animals and plants.

DIGESTIBLE ENERGY REQUIREMENTS FOR MAINTENANCE OF BODY MASS OF WHITE-TAILED DEER IN SOUTHERN TEXAS

Abstract Previous experiments designed to estimate daily digestible energy requirements for body-mass maintenance in white-tailed deer (Odocoileus virginianus) were conducted using deer adapted to northern environments. However, animals adapted to warmer, drier environments may have lower metabolic requirements than their temperate conspecifics. We conducted a feeding trial to estimate digestible energy requirements for maintenance of body mass of white-tailed deer in southern Texas and to determine if those requirements vary over time. By restricting dietary levels of digestible energy and measuring deer body mass every 3 days for a 30-day period, we developed a model relating digestible energy intake and change in body mass over time for 11 adult, nongravid females during autumn. Predicted daily digestible energy intake requirements for body-mass maintenance (kJ/kg body mass0.75) ranged from 820 ± 168 SE at trial initiation to 357 ± 42 at trial completion. Our experiment demonstrated that daily digestib...

Physiological correlates to off-road cycling performance

The aim of this study was to examine the relationships between maximal and submaximal tests for aerobic fitness and performance in an off-road cross-country circuit race. Thirteen competitive off-road male cyclists participated in the study. Peak oxygen uptake (VO2peak), peak power output, and lactate thresholds corresponding to 1 mmol · l-1 above baseline (lactate threshold) and to 4 mmol · l-1 (onset of blood lactate accumulation) were measured during an incremental cycling test. Race time and final ranking within the same group of cyclists were determined during a cross-country off-road competition. All correlations between the measured parameters of aerobic fitness and off-road cycling performance were significant, particularly between race time and physiological parameters scaled to body mass0.79 (r = -0.68 to - 0.94; P < 0.05) and between final ranking and physiological parameters expressed relative to body mass0.79 (r = -0.81 to - 0.96; P < 0.001). Moreover, there was a large difference (effect sizes = 1.12 - 1.70) in all measured parameters of aerobic fitness between the group of six cyclists with a race time above the median and the group of six cyclists with a race time below the median (P < 0.05). In conclusion, the results of this study provide empirical support to the widespread use of these maximal (VO2peak, peak power output) and submaximal (lactate thresholds) parameters of aerobic fitness in the physiological assessments of off-road cyclists. Furthermore, our results suggest body size should be taken into account when evaluating such athletes.

Standard and maximal metabolic rates of goannas (Squamata:Varanidae)

Standard metabolic rate and maximal metabolic rate during forced exercise are examined for nine species of goanna (genus Varanus), with body mass varying from 10 to 3,750 g. At 35 degrees C, the common pooled mass exponent for standard metabolic rate is 0.97 and at 25 degrees C it is 0.89, with considerable variation between species (0.43-1.20). Standard metabolic rate at 35 degrees C scales interspecifically with body mass0.92 and at 25 degrees C with body mass0.87. The Q10 for standard metabolic rate is approximately 2.5 between 25 degrees and 35 degrees C. At 35 degrees C, maximal metabolic rate scales intraspecifically with body mass0.79 and scales interspecifically with body mass0.72. Factorial metabolic scope ranges from nine for the larger species to 35 for the smaller species; it scales with body mass-0.199 at 35 degrees C. The maximal metabolic rate of 6.36 mL O2 g-1 h-1 for Varanus caudolineatus is the highest recorded for any squamate. Variations from the interspecific regression line appear to have some ecological significance. Varanus tristis (a widely foraging arboreal goanna) and Varanus eremius (a widely foraging terrestrial goanna) have a higher standard metabolic rate than Varanus acanthurus (a sedentary terrestrial goanna). The three arboreal goannas (Varanus caudolineatus, Varanus gilleni, and Varanus tristis) have a higher maximal metabolic rate than the terrestrial species (Varanus brevicauda, V. eremius, V. acanthurus, Varanus gouldii, Varanus rosenbergi, and Varanus panoptes).

Locomotor patterns and costs as related to body size and form in teiid lizards

Stride parameters and gaits were examined in seven species of teiid lizards in an attempt to understand size‐dependent variation of locomotor patterns. Scaling of body dimensions to body mass revealed that axial measures conformed to geometric similarity, whereas the limb segments exhibited an allometry which was statistically significantly less than geometric similarity. Variations in the relationships between stride lengths, stride frequencies and duty factors (% of the stride that foot contacts ground) represented locomotor specializations and were not strictly size‐dependent among species. At body length equivalent velocities, stride length and stride frequency scaled to body mass0.40±0.06 and 0.09±0.03, respectively. Cost during locomotion at body length equivalent velocities could be estimated by the square of the product of stride length and stride frequency. Plotting the cost during locomotion for geometrically similar lizards against body mass yielded an estimate of the cost during locomotion that was proportional to mass0.62±0.11. An estimate of the mass‐specific cost during locomotion at body length‐equivalent velocities scales to mass−0.38±0.11. Because the limbs of these lizards exhibit an allometry less than geometric similarity, a correction of the estimate of the mass‐specific cost during locomotion could be obtained by factoring in the effect of increased locomotor costs associated with relatively shorter pelvic limbs in larger lizards. The allometrically corrected estimate of the mass‐specific cost during locomotion was proportional to mass−0.31. This estimated regression, which is the relatiue cost of transport for a single, morphologically conservative family of lizards, predicts a slope quite close to that derived from studies of oxygen requirements during locomotion in lizards of several families (slope= ‐0.28, John‐Alder, Garland &amp; Bennett, 1986) and in mammals (slope= ‐0.32, Taylor, Heglund &amp; Maloiy, 1982).

Water flux and energy use in wild house mice (Mus domesticus) and the impact of seasonal aridity on breeding and population levels.

Water turnover rate (WTR), urine concentration and field metabolic rate (FMR) were examined in house mice, Mus domesticus, permanently inhabiting roadside verge areas and seasonally invading crops in semi-arid wheatlands in South Australia. FMR was approximately proportional to body mass0.5 and mean values varied from 4.8 ml CO2 g-1h-1 (2.9 kJ g-1d-1) in autumn and winter, to 7.0 ml CO2 g-1h-1 (4.2 kJ g-1d-1) in maturing crops during spring. WTR was independent of body mass, indicating that larger mice were selecting a diet containing moister foods. WTR was low in summer and high in winter, and in mice from crops varied from 165 ml l-1 body water d-1 (122 ml kg-1d-1) to 1000 ml l-1d-1 (725 ml kg-1d-1). Seasonal changes in WTR were less extreme on the roadside, where a greater diversity of food was available. In the crops, breeding occurred throughout summer during two of three years, but the population increased only in the one summer when mice had marginally higher WTR. On the roadside breeding and population growth were continuous during summer, except in a drought year. Avcrage urine concentration was inversely related to WTR, and varied from 2.0 to 4.8 Osm l-1. The data indicate that the water conserving abilities of mice equal those of many desert rodents. The water conserving abilities of mice living in crops during summer were fully extended, and in some years aridity limited breeding success and population levels. The degree of moisture stress to which mice are exposed during summer appears to depend not only on rainfall but also on other factors such as availability of food and shelter, and the level of weed infestation in crops.

Comparative Field Energetics of Two Macropod Marsupials and a Ruminant.

Field metabolic rates (FMRs) and water influx rates were measured via the doubly labelled water method in wild Tasmanian pademelons and grey kangaroos living in the Jock Marshall Reserve at Clayton, Victoria, and in wild black-tailed deer free-ranging within a nature reserve at Davis, California. Deer expended more than 3 times more energy per day than similar sized grey kangaroos. Feeding rates required to achieve energy balance were estimated from FMRs along with an estimate of metabolizable energy content of the food. The estimated feeding rates for pademelons and kangaroos were combined with similar values for 5 other species of macropods to calculate an allometric (scaling) relationship for food requirements of macropod marsupials. Feeding rate had the following relationship to body mass: g food (DM) consumed per day = 0.20 g body mass0.79 (r2 = 0.94). The findings reported herein should be useful for predicting the approximate food requirements of free-ranging macropods and deer for purposes of ecological modelling, conservation efforts and management programmes.

Cold-induced thermogenesis in younger and older Fischer 344 rats following exercise training

Pages R908–R916: Roger B. McDonald, Barbara A. Horwitz, and Judith S. Stern. “Cold-induced thermogenesis in younger and older Fischer 344 rats following exercise training.” Page R912: the y-axis label of Fig. 4 should read: VO2 [ml/(min x kg body mass0.67)]. Page R913: substitute corrected Table 3: (See PDF)

Structural and Functional Determinates of Metabolic Rate

SYNOPSIS. Standard metabolic rates are principally determined by relatively few factors: temperature, mass, and phylogenetic affinities. 1) Temperature. Body temperature has pervasive effects on biological processes through the influence of temperature on the activity of metabolically important enzymes: metabolic rates double or triple when body temperature increases 10°C. The absolute levels of metabolism that any temperature establishes may be subject to acclimatory or evolutionary change by alteration of enzyme composition or structure. In endotherms, the effects of this basic thermal dependence may be overcome by the physiological regulation of body temperature, but such regulation is very energetically expensive. 2) Body mass. Metabolic rate scales interspecifically with body mass0.75. We understand to a degree how animals are structured to produce this observed allometric dependence of metabolism on mass, principally by quantitative differences in cellular metabolism that can be attributed to differential mitochondrial content. But we do not understand why animals are so structured or what exactly is the reason for this particular mass exponent. 3) Phylogeny. Metabolic level varies among taxa, and the phylogenetic history and relative associations of an animal are important determinates of energy expenditure. Mammals and birds have substantially greater metabolic rates than do ectothermic vertebrates, even at common body temperatures. However, even within vertebrate classes, metabolic level varies among orders. The principle of symmorphosis has been proposed to describe the structural consequences of functional design and the morphogenetic response of biological systems to functional need.