Metabolic Costs Of Maintenance Research Articles

Larger guts and faster growth in mice selected for high basal metabolic rate.

Postnatal growth in birds and mammals is the time of highest vulnerability and relatively high energy demands and therefore shapes the organisms' future outcomes. Several different factors might impose limitations on growth in juveniles, one of them being the efficiency of the digestive process and size of the gastrointestinal tract. We tested the gut size-growth rate relationship using a unique experimental model-mice from a selection experiment designed to produce two lines with divergent levels of basal metabolic rate (BMR): the high BMR (H-BMR) and low BMR (L-BMR) line types. These lines differ with respect to not only BMR, but also correlated traits-internal organ size and food intake. Applying a cross-fostering design and a thermoregulatory burden imposed by shaving the mothers, we demonstrated that the mass of intestine strongly affected the growth rate, with the H-BMR pups having larger intestines and growing faster, and with reduced growth rate of pups of both lines nursed by shaved L-BMR mothers. Our study also provides a functional link between high growth rate of neonates and high BMR of adults, partly reflecting metabolic costs of maintenance of their guts.

Positive allometry of sexually selected traits: Do metabolic maintenance costs play an important role?

Sexual selection drives the evolution of some of the most exaggerated traits in nature. Studies on sexual selection often focus on the size of these traits relative to body size, but few focus on energetic maintenance costs of the tissues that compose them, and the ways in which these costs vary with body size. The relationships between energy use and body size have consequences that may allow large individuals to invest disproportionally more in sexually selected structures, or lead to the reduced per-gram maintenance cost of enlarged structures. Although sexually selected traits can incur energetic maintenance costs, these costs are not universally high; they are dependent on the relative mass and metabolic activity of tissues associated with them. Energetic costs of maintenance may play a pervasive yet little-explored role in shaping the relative scaling of sexually selected traits across diverse taxa. Also see the video abstract here: https://youtu.be/JyuoQIeA33Q.

Influence of feed ration size on somatic and muscle growth in landlocked dwarf and farmed Atlantic salmon Salmo salar.

We examined the possible adaptation of the dwarf Bleke population of Atlantic salmon Salmo salar from Lake Byglandsfjord in southern Norway to limited food resources. The growth performance and muscle development in juvenile Bleke and farmed S. salar under satiated or restricted (50%) feeding were examined for 10 months, starting 3 weeks after first-feeding stage. Four-thousand fish were divided into four replicated groups and random samples of 16-40 fish per group were measured six times during the experiment. The two strains showed no significant difference in mean body mass when fed restricted ration, but the individual variation was considerably higher in the farmed fish. Both Bleke and farmed S. salar grew significantly faster when fed to satiation, but the farmed S. salar showed much higher gain in mass and were three times heavier (201.5 g vs 66.7 g) and possessed twice as many fast muscle fibres (179,682 vs 84,779) compared with landlocked S. salar after 10 months. Farmed fish fed full ration displayed both hypertrophic and hyperplasic muscle growth, while the increased growth in Bleke S. salar was entirely associated with a larger fibre diameter. The landlocked Bleke strain has apparently adapted to low food availability by minimising the metabolic costs of maintenance and growth through reduced dominance hierarchies and by an increase in average muscle fibre diameter relative to the ancestral condition.

The effect of food conditioning on feeding and growth responses to variable rations in fast and slow growing spat of the Manila clam (Ruditapes philippinarum)

Two groups of clam spat (Ruditapes philippinarum) belonging to different growth categories of fast (F) and slow (S) growers were each conditioned to diets of low and high phytoplankton concentration (0.3 and 1.0mg POMl−1, respectively), and their components of energy balance measured across a range of food concentrations, in order to ascertain the combined contribution of endogenous and exogenous (food ambient) factors to growth performance. Analysis of the physiological traits indicates that both higher food acquisition and higher metabolic efficiencies were responsible for faster growth rates recorded with F spats in the tested range of food concentration (0.3 to 1.1mg POMl−1). In both types of clams acute response to increased food availability involved ingestion regulation by adjusting clearance rates was observed, thus helping to maintain nearly constant absorption efficiency values (around 70%) across food levels. Optimal ration (that providing maximum ingestion and scope for growth values) was found to rise from mid- (0.65mg POMl−1) to high food concentration (1.1mg POMl−1) following the change in conditioning from low to high food levels. Increased capacity to process food efficiently is accounted for by greater digestive investments in clams conditioned to high ration that results in increased metabolic costs of maintenance (recorded as rates of oxygen consumption after 4days starvation), and associated to decline in growth performance during transitory exposure to poor food conditions.

Metabolic costs of hybridization in Newts

Abstract. Heterospecific hybrids often suffer from a lowered fitness relative to parental species. Contextdependent intrinsic costs of hybridization are partially due to a malfunction in cell biochemical machinery that affects metabolic rates at the organismal level. This study examines whether heterospecific hybridization influences the metabolic costs of maintenance in F1 hybrids between closely related newts, Triturus carnifex and T. dobrogicus. When controlled for body size, oxygen consumption in hybrid newts was 59–76 % higher than in the parental species. This suggests that high standard metabolic rates in hybrids may contribute to the costs of hybridization in newts.

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.

The role of leaf height in plant competition for sunlight: analysis of a canopy partitioning model

A global method of nullcline endpoint analysis is employed to determine the outcome of competition for sunlight between two hypothetical plant species with clonal growth form that differ solely in the height at which they place their leaves above the ground. This difference in vertical leaf placement, or canopy partitioning, produces species differences in sunlight energy capture and stem metabolic maintenance costs. The competitive interaction between these two species is analyzed by considering a special case of a canopy partitioning model (RR Vance and AL Nevai, J. Theor. Biol. 2007, 245:210-219; AL Nevai and RR Vance, J. Math. Biol. 2007, 55:105-145). Nullcline endpoint analysis is used to partition parameter space into regions within which either competitive exclusion or competitive coexistence occurs. The principal conclusion is that two clonal plant species which compete for sunlight and place their leaves at different heights above the ground but differ in no other way can, under suitable parameter values, experience stable coexistence even though they occupy an environment which varies neither over horizontal space nor through time.

Fever and sickness behavior during an opportunistic infection in a free-living antelope, the greater kudu (Tragelaphus strepsiceros)

To study their thermal responses to climatic stress, we implanted seven greater kudu (Tragelaphus strepsiceros) with intra-abdominal, brain, carotid, and subcutaneous temperature data loggers, as well as an activity logger. Each animal was also equipped with a collar holding a miniature black globe thermometer, which we used to assess thermoregulatory behavior. The kudu ranged freely within succulent thicket vegetation of the Eastern Cape Province, South Africa. The kudu spontaneously developed a bacterial pneumonia and consequent fever that lasted between 6 and 10 days. The fever was characterized by a significant increase in mean 24-h abdominal temperature from 38.9 +/- 0.2 degrees C to 40.2 +/- 0.4 degrees C (means +/- SD, t(6) = 11.01, P < 0.0001), although the amplitude of body temperature rhythm remained unchanged (t(6) = 1.18, P = 0.28). Six of the kudu chose warmer microclimates during the fever than when afebrile (P < 0.0001). Despite the selection of a warmer environment, on the first day of fever, the abdominal-subcutaneous temperature difference was significantly higher than on afebrile days (t(5) = 3.06, P = 0.028), indicating vasoconstriction. Some kudu displayed increased frequency of selective brain cooling during the fever, which would have inhibited evaporative heat loss and increased febrile body temperatures, without increasing the metabolic maintenance costs of high body temperatures. Average daily activity during the fever decreased to 60% of afebrile activity (t(6) = 3.46, P = 0.014). We therefore have recorded quantitative evidence for autonomic and behavioral fever, as well as sickness behavior, in the form of decreased activity, in a free-living ungulate species.

The potential of producing heterotrophic bacteria biomass on aquaculture waste

The effluent from the drumfilter of a recirculation aquaculture system was used as substrate to produce heterotrophic bacteria in suspended growth reactors. The effects of organic carbon supplementation (0, 3, 6, 8 g/l sodium acetate) and of hydraulic retention times (11–1 h) on bacteria biomass production and nutrient conversion were investigated. Bacteria production, expressed as volatile suspended solids (VSS), was enhanced by organic carbon supplementation, resulting in a production of 55–125 g VSS/kg fish feed (0.2–0.5 g VSS/g carbon). Maximum observed crude protein production was ∼100 g protein/kg fish feed. The metabolic maintenance costs were 0.08 Cmol/Cmol h, and the maximum growth rate was 0.25–0.5 h −1. Ninety percent of the inorganic nitrogenous and 80% of ortho-phosphate were converted. Producing bacteria on the drumfilter effluent results in additional protein retention and lowers overall nutrient discharge from recirculation aquaculture systems.

The metabolic cost of reproduction in an oviparous lizard

Abstract1. Studies of reproductive effort in ectotherms have focused primarily on the energetic investment in gamete production; much less is known about the indirect energetic costs of reproduction, such as increased metabolic costs of maintenance or activity.2. The metabolic cost of reproduction in the oviparous lizard, Sceloporus undulatus, was investigated by measuring the metabolic rate of females prior to and following oviposition.3. The metabolic rates of gravid females were adjusted for embryonic metabolism by subtracting the metabolic rate of egg clutches, measured immediately after oviposition.4. The metabolic rate of females when gravid was elevated by 122% compared with that when non‐gravid. The difference was not detected until the metabolic rates of gravid females were adjusted for the metabolic rates of the embryos.5. The increment in metabolic rate associated with reproduction was not correlated with clutch mass or body mass, indicating that different components of reproductive effort (i.e. metabolism vs gametic investment) may not covary in a predictable fashion.6. Indirect energetic costs of reproduction constitute a substantial portion of the reproductive effort of female S. undulatus, and should be incorporated into theoretical considerations of life history.

Time and Energy Constraints in Pinniped Lactation

Previous reviews have recognized patterns of lactation in pinnipeds divided along phylogenetic lines. This study extended previous models of lactation in pinnipeds by explicitly taking into account all the energetic costs to mothers. Based on an analysis of time-energy budgets, the feasible lactation strategy for a species can be shown to depend on body mass. Due to increased metabolic costs of maintenance, species with a large body mass cannot normally sustain lactation by foraging during lactation unless they have access to rich local prey resources. Consequently, large pinnipeds must normally sustain lactation from body reserves. This disadvantage is compensated in large pinnipeds by freedom to forage in support of offspring at greater range whereas small pinnipeds are restricted to foraging within the locality of the pupping colony. In the absence of correlations between major life-history variables and body mass in pinnipeds, the principal patterns of lactation are likely to be different solutions to the trade-off between foraging on a relatively rich prey resource at long range and foraging on a poorer prey resource within a restricted range. Hence phylogeny may be less important than adaptation in the evolution of pinniped lactation.

Time and Energy Constraints in Pinniped Lactation

Previous reviews have recognized patterns of lactation in pinnipeds divided along phylogenetic lines. This study extended previous models of lactation in pinnipeds by explicitly taking into account all the energetic costs to mothers. Based on an analysis of time‐energy budgets, the feasible lactation strategy for a species can be shown to depend on body mass. Due to increased metabolic costs of maintenance, species with a large body mass cannot normally sustain lactation by foraging during lactation unless they have access to rich local prey resources. Consequently, large pinni‐peds must normally sustain lactation from body reserves. This disadvantage is compensated in large pinnipeds by freedom to forage in support of offspring at greater range whereas small pinnipeds are restricted to foraging within the locality of the pupping colony. In the absence of correlations between major life‐history variables and body mass in pinnipeds, the principal patterns of lactation are likely to be different solutions to the trade‐off between foraging on a relatively rich prey resource at long range and foraging on a poorer prey resource within a restricted range. Hence phylogeny may be less important than adaptation in the evolution of pinniped lactation.

Towards a physiological and genetical understanding of the energetics of the stress response

We consider stress as an environmental change that results in reduction of net energy balance (i.e. growth and reproduction). Reduced energy balance restricts the environmental range of an organism and may change the environmental optima at which maximum production can be achieved. We emphasize individual differences in net energy balance and the interrelationships among genetic heterozygosity, rate of protein synthesis, efficiency of protein synthesis and whole organism measures of both routine and maintenance metabolic rate. Lastly, we consider the consequences of genetically determined individual differences in metabolic maintenance costs within the context of variable environments and how genetic/environmental interactions can define individual responses to environmental extremes.

Energetic Constraints of Juvenile Chum Salmon (Oncorhynchus keta) Migrating in Estuaries

Experiments on fish feeding behavior, field measures of fish sizes, migration rate, and prey resources, and an energetic growth model are used to evaluate the growth of juvenile chum salmon (Oncorhynchus keta) during outmigration in an estuary. Fish growth is defined as the difference between energy intake and metabolic costs. Energy intake is estimated from prey densities and foraging parameters, namely pursuit swimming speeds and energetic expenditures, and prey handling and encounter rates. Relationships for foraging parameters as functions of fish sizes and field prey abundance are used to evaluate energy intake by fish in the estuary. This information and calculations of metabolic costs allow predictions of fish growth during the migration. Results show that metabolic costs of maintenance and migration lie in a delicate balance with food intake and growth. Growth efficiencies exceeding 20% occur when metabolic expenditures decline and energy intake rates permit growth without depletion of the food supply. Defining such energetic balances facilitates characterization of carrying capacities of coastal ecosystems and has implications for enhancement of juvenile fish growth and, in turn, fish survival and production at sea.

The cause of reduced growth of Manduca sexta larvae on a low-water diet: Increased metabolic processing costs or nutrient limitation?

Relative growth rates and nitrogen accumulation rates are lower for third-instar Manduca sexta larvae on an artificial diet containing 65% water than on one containing 82% water, due to reduced efficiencies of conversion of digested food and digested nitrogen into larval biomass. Uric acid production is 2.0–2.5-fold greater, and non-feeding respiration rates 16.0% higher in the larvae on the low-water diet. Food is the major source of water for the larvae, with metabolic water making only a minor contribution to water input. Faecal excretion is the major avenue of water loss, although a significant amount of water is also lost by transpiration. Larvae from the low-water diet retain and use a higher percentage of the water they gain than larvae from the high-2ater diet (49.4% vs 41.9%). They produce much drier faeces (48.1% water vs 77.3% water), and, because their tissues are less hydrated (81.3% water vs 88.1% water), they synthesize 70% more new, fully hydrated tissue from a given amount of water than larvae from the high-water diet. We discuss problems involved in the use of determinations of efficiency of conversion of digested food in establishing causal links between diet, growth, and metabolic maintenance costs, and also offer a definition of food processing costs that distinguishes them from metabolic costs attributable to other processes, such as food acquisition, growth, and moulting. We conclude that reduced growth and reduced efficiency of conversion of digested food on low-water diets are due to limitation in the amount of water available for the synthesis of new hydrated tissue, and not to the imposition of higher food processing costs.

Metabolic maintenance costs of the suspension feeder Styela plicata

The bioenergetic basis of the biannual reproductive cycle of the solitary tunicate Styela plicata was investigated in order to evaluate hypotheses concerning the lack of larval settlement in summer. The rate of ingestion and absorption efficiency were measured in order to provide an estimate of the rate at which material was made available for maintenance, growth, and reproduction. At a given temperature the rate of ingestion was proportional to the 0.7 power of wet mass. the ingestion rate increased rapidly with increasing temperature between 12° and 18°C (Q10≃3), but was independent of temperature between 18° and 28°C. Absorption efficiency was independent of temperature and body size and averaged approximately one-third for both carbon and nitrogen. Metabolic maintenance costs were estimated from measurements of oxygen consumption and excretion of ammonia and urea reported for s. plicata. These require only 18±11% of the carbon and 37±22% of the nitrogen absorbed from the gut of S. plicata over the temperature range 12° to 28°C. Metabolic maintenance makes no excessive demands on the material absorbed in the gut at a particular time of year, and a surplus of carbon and nitrogen substrate is available throughout the year for growth and reproduction. Predation on larvae and young adults may be responsible for the low rate of settlement observed in summer months.

OXYGEN UPTAKE OF THE SOLITARY TUNICATE STYELA PLICATA.

1. The oxygen consumption of the solitary tunicate Styela plicata was measured in order to estimate routine metabolic maintenance costs of the animal throughout the year. 2. The acclimatized oxygen consumption of Styela is proportional to the 0.7 power of body weight; this value is independent of the acclimatization temperature. 3. Q10 declines with increasing temperature, averaging 3 between 10° and 20° C, and 1.7 between 20° and 30° C. 4. Disproportionately large metabolic costs of routine activity cannot be invoked to explain the apparent lack of reproduction by Styela plicata during the warmest summer months. 5. The northern limit of Styela plicata is in the vicinity of Cape Hatteras, North Carolina. Winter mortality of adults is likely to limit the northern extension of Styela beyond Hatteras, and dislodgement from substrate during cold (growth inhibited) periods is suggested as one cause of winter mortality. 6. At temperatures greater than 10° C, oxygen uptake of Styela is independent of oxygen tension at normoxic conditions. An analysis of the critical oxygen tension as a function of temperature and body size suggests that ciliary activity may decrease the oxygen diffusion distance in the branchial sac at increased temperatures, and that the surface area per unit volume oxygen consumed may increase with increasing body size because of the demands of filter-feeding on the branchial sac.