Energy budget and foraging behaviour of the Cape gannet Morus capensis during the breeding season

Includes abstract.Includes bibliographical references.This thesis deals with the energy expenditure of free-ranging Cape gannets Morus capensis breeding at Malgas Island, South Africa. I sought to determine the energy budget of family units and to extrapolate this to the whole population. Energy expenditure was measured using the doubly labelled water technique on adults and chicks. CO2 production was determined from ratios of isotope turnover, and converted into energy expenditure using a factor suitable for a fish-eating seabird

From growth to extinction : explored by life history and metabolic theory

The laws of energy and material conservation are fundamental principles across various scales and systems. Based on the conservation laws, I derive several theoretical models to understand mechanisms behind the energy budget of ontogenetic growth and the pattern of the late Pleistocene extinction of megafauna in the Americas. First, I present a model, empirically grounded in data from birds and mammals, that correctly predicts how growing animals allocate food energy between synthesis of new biomass and maintenance of existing biomass. Previous energy budget models have typically been based on rates of either food consumption or metabolic energy expenditure. The model provides a framework that reconciles these two approaches and highlights the fundamental principles that determine rates of food assimilation and rates of energy allocation to maintenance, biosynthesis, activity, and storage. The model predicts that growth and assimilation rates for all animals should cluster closely around two canonical curves. Second, the previous model, which focuses on endotherms, has been extended to understand effects of temperature on the energy budget of ontogenetic growth of ectotherms. A tendency for ectotherms to develop faster but mature at smaller body sizes in warmer environments has been studied for decades, and is called the temperature size rule (TSR). It can be explained by a simple model in which the rate of growth or biomass accumulation and the rate of development or differentiation have different temperature dependence. The model accounts for both TSR and the less frequently observed reverse-TSR, predicts the fraction of energy allocated to maintenance and synthesis over the course of development, and the temperature independent growth efficiency. It also predicts that less total energy is expended when developing at warmer temperatures for TSR and vice versa for reverse-TSR. It has important implications for effects of climate change on ectothermic animals and also provides how selection may lead to the evolution of both TSR and reverse-TSR. Finally, based on mammalian life history and life history scaling relationships, an exploitation-extinction theory has been developed for the rate of human harvest in the disappearance of the Pleistocene megafauna in the Americas. The theory demonstrates that the added mortality of human harvest on populations need not be selective to produce a size-biased extinction. The variation in the adult natural instantaneous mortality rate and/or the maximum recruitment compensation at any body mass are main components determining the probability of extinction. The theory successfully predicts the shapes of the extinction probability curves for the late Pleistocene extinction in the Americas. It provides a theoretical basis to challenge a major criticism of the overkill theory that early Paleoindian hunters had to be extremely selective to have produced the highly size-biased pattern characteristic to the late Pleistocene extinction of megafauna in the Americas

Metabolic reconstitution of germ-free mice by a gnotobiotic microbiota varies over the circadian cycle.

The capacity of the intestinal microbiota to degrade otherwise indigestible diet components is known to greatly improve the recovery of energy from food. This has led to the hypothesis that increased digestive efficiency may underlie the contribution of the microbiota to obesity. OligoMM12-colonized gnotobiotic mice have a consistently higher fat mass than germ-free (GF) or fully colonized counterparts. We therefore investigated their food intake, digestion efficiency, energy expenditure, and respiratory quotient using a novel isolator-housed metabolic cage system, which allows long-term measurements without contamination risk. This demonstrated that microbiota-released calories are perfectly balanced by decreased food intake in fully colonized versus gnotobiotic OligoMM12 and GF mice fed a standard chow diet, i.e., microbiota-released calories can in fact be well integrated into appetite control. We also observed no significant difference in energy expenditure after normalization by lean mass between the different microbiota groups, suggesting that cumulative small differences in energy balance, or altered energy storage, must underlie fat accumulation in OligoMM12 mice. Consistent with altered energy storage, major differences were observed in the type of respiratory substrates used in metabolism over the circadian cycle: In GF mice, the respiratory exchange ratio (RER) was consistently lower than that of fully colonized mice at all times of day, indicative of more reliance on fat and less on glucose metabolism. Intriguingly, the RER of OligoMM12-colonized gnotobiotic mice phenocopied fully colonized mice during the dark (active/eating) phase but phenocopied GF mice during the light (fasting/resting) phase. Further, OligoMM12-colonized mice showed a GF-like drop in liver glycogen storage during the light phase and both liver and plasma metabolomes of OligoMM12 mice clustered closely with GF mice. This implies the existence of microbiota functions that are required to maintain normal host metabolism during the resting/fasting phase of circadian cycle and which are absent in the OligoMM12 consortium

Starving to grow:The ecology and evolution of growth curve plasticity

All organisms grow in size throughout their life. Some species display a largely constant growth curve, while the growth curve of other species is largely plastic and therefore strongly depends on environmental factors such as the resource availability. This thesis explores how the level of growth curve plasticity affects the ecological and evolutionary dynamics of a population. On the individual level, growth curve plasticity is tightly intertwined with the energy allocation schemes of an individual and the energetic trade-offs between growth, reproduction and maintenance. This is modeled using a simple dynamic energy budget model. Fluctuations in the environment accumulate in the size of individuals if growth is largely plastic. As a consequence, the level of growth curve plasticity strongly influences the size-structure of a population. This size-structure can therefore contain valuable information about the environmental limitations experienced by a population. The first part of this thesis explores how this information can be deduced from size measurements of individuals from natural populations such as North Sea fish stocks. The second part of this thesis uses size-structured models to show that the dynamics of a population is driven by limitations in either growth or reproduction. These two regimes show differences in the population structure, the occurrence and type of population dynamic cycles, the effects of harvesting and optimal fishing strategies. Overall, this thesis shows that the level of growth curve plasticity should be considered when exploring the dynamics of structured populations on any level of biological organization

Urban Productivity & Spatial Patterns Across Scales

Understanding the nuances at play across different spatial scales is of crucial importance when considering urban economic-energetic size-cost performance, specifically when longer-term consequences are considered. Through the application of an allometric understanding of cities, a more nuanced narrative is offered highlighting the interplay of urban productivity and spatial configurations of human interactions across scales. This is presented in three parts. In the initial examination of the urban economic-energetic size-cost balance across spatial scales, we seek new insights on the effects of scale in relation to urban connectivity and density for maximizing urban size-cost balance. For this, we use the urban system in England and Wales as a topical testbed where agglomeration-based arguments have been used in support of better inter-city connectivity in order to address a historic North-South regional economic productivity divide. The inadequate connectivity thought to be affecting the economic performance across the urban network in England and Wales, however, is shown to permeate across spatial scales. More broadly, this points at a scale-induced hierarchy of urban connectivity concerning potential improvements needed at inter- and intra-city scales. This is followed by an examination of the universality and transferability of scaling insights, and their nuances, between different cities and systems of cities. Considering the current transport schemes designed to address the North-South economic gap, we examine the continental comparisons drawn specifically from the inter-city transport infrastructure connecting the Randstad in the Netherlands and Rhine-Ruhr metropolitan region in Germany. Our examination points towards fundamental differences that exist in the structure and distribution of population density across the countries and their city-regions across various scales. Additionally, the cross comparison demonstrates that, although scaling insights are transferable between urban systems, a simple multi-scale assessment of individual systems of cities in isolation is sufficient when investigating urban connectivity from an urban allometric point of view. Finally, returning full circle to the effects of spatial scales and distance on the geographical patterns of urban connectivity, we review a mathematically grounded approach to sort and organize the intra- and inter-city connectivity hierarchy while matching complementary infrastructural needs based on size-cost balances for a number of different scenarios. Together, this narrative provides a somewhat enhanced and most crucially spatially multi-scale examination of the arguments regarding connectivity and agglomeration in an urban context

The role of physical activity, cardiorespiratory fitness and exercise on the autonomic and arterial systems of healthy adolescents

Cardiovascular diseases (CVD) are the leading cause of death worldwide and the atherosclerotic process that precedes CVD starts during childhood. Physical activity (PA), cardiorespiratory fitness (CRF) and exercise are well known as preventive strategies for CVD. One possible mechanism for such prevention is the role of PA, CRF and exercise on the arterial and autonomic systems. The aim of this thesis was to investigate using observational and experimental studies the role of PA, CRF and exercise on the autonomic and arterial systems of healthy adolescents. Chapter 4 systematically reviewed observational cross-sectional studies and provided level one evidence for a significant and positive association between resting parasympathetic function and moderate-to-vigorous PA in youth. Chapter 4 also indicated that gaps exist in the literature such as the associations between PA intensities, CRF and heart rate variability (HRV). These findings were furthered in Chapter 5 which showed that vigorous PA (VPA) and moderate PA (MPA) were positively related with HRV at rest and cardiac autonomic recovery following exercise in adolescents. In Chapter 6 a high-fat meal was used aiming to increase CVD risk in the postprandial state, and it was demonstrated that PA levels and CRF are not significantly associated with postprandial HRV and arterial stiffness in adolescents. Aiming to investigate possible associations between the vascular and autonomic system, measures of baroreflex sensitivity (BRS) were introduced. Chapter 7 showed that BRS and its autonomic and vascular components present a between-day coefficient of variation lower than 20% whilst within day coefficient of variations were lower than 34% in adolescents. In Chapter 8 acutely following high- and moderate-intensity interval exercise a decrease in blood pressure was observed concomitantly with decreases in BRS. This was mainly mediated by decreases in the autonomic modulation, and the duration of the decreases in blood pressure was higher following high-intensity interval exercise. Chapter 9 extended these findings by demonstrating that the changes in BRS following the ingestion of glucose was not altered by the high or moderate-intensity exercise performed before glucose ingestion. Chapter 10 showed that following four weeks of high-intensity exercise interval training no improvements were observed in BRS and its autonomic and vascular components at rest or acutely following exercise. Collectively, the present thesis contributes significantly to the literature by providing novel evidence in healthy adolescents on the role of PA intensities, CRF and exercise on the arterial and autonomic systems at rest, acutely following exercise and in the postprandial state. The results gathered in this thesis indicate potential of the autonomic and vascular function as targets of CVD risk reduction in youth.Coordenação de aperfeiçoamento de pessoal de nível superior - CAPES. Brazi

The physical, environmental, and evolutionary determinants of biological architecture

Thesis (Ph. D. in Physical Biology)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 201-224).The relationship between structure and function is a longstanding and central topic in biology, evolution, and ecology. The importance of morphology is clearly visible in the diverse forms taken by innumerable organisms in order to perform a myriad of functions. Examining the great variety of morphological characteristics it would seem that the overall principle of evolution is the only way to generalize the observed diversity: given differences in environments and random biological variation a great multitude of body plans have been invented as adaptations to many dynamic habitats given specific evolutionary histories. In this thesis I will show how focusing on diverse organisms makes it possible to identify common first-order laws of evolutionary organization. More specifically I will show how these common laws derive from a connection between organism structure, physical limitations, environmental constraints, and basic metabolic, biochemical, or energetic principles. Furthermore, I will show how this top level of biological organization holds significant predictive power for regional ecology and for interpreting the general trends of evolutionary history. In Chapter 2 we begin by deriving a model for the growth of single cells and populations of cells. This model is based on the partitioning of metabolic resources and the scaling relationship between metabolism and body size. We show that the growth of diverse classes of organisms is connected by common unit energetics. However there exist striking differences in the broad trends between growth rate and body size across these different classes and we show that this is a consequence of major evolutionary transitions which adjust the partitioning of metabolic resources. We interpret major evolutionary transitions to occur in response to energetic limitations. We also find that multicellular living for unicellular organisms provides a metabolic and reproductive advantage. In Chapters 3 and 4 we further investigate these features in microbial biofilms which exhibit rich spatial patterning. Using a mathematical model and experimentation we find that the tall vertical structures produced by these biofilms have optimal geometry for resource uptake and the growth efficiency of the entire colony. Our model allows us to predict the observed changes in feature geometry given alterations to the environmental conditions that the biofilms are grown in. Furthermore, we are able to show that the morphology of these structures is dependent on single cell physiology. For example, single genetic knockouts of flagellar motility radically alter the temporal dynamics of feature spacing. Our work highlights morphology as a central property in multicellular organisms which mediates the interaction between environmental conditions and physiology. In Chapter 5 we highlight the importance of morphology in complex multicellular life where we develop a general model of tree architecture which we link to physiological success within a given environment. Although this model is general, uses only tree size as a governing parameter, and does not consider speciation we are able use local resource availability to predict broad regional patterns in plant traits such as maximum tree height. Each of these chapters highlights the importance of structure and morphology at multiple biological scales. In Chapter 6 we show how the importance of structure extends to the genetic level where the specific encoding of a gene can have implicit information and functionality beyond the basic translation of codons. We investigate the observed implicit function of dramatic and frequent changes in the mutation rate of an organism given the structure of the mutL gene. We show mathematically that altering mutation rates is an evolutionarily advantageous strategy, and we show bioinformatically that the specific genetic structure that gives rise to this trait is under positive evolutionary selection.by Christopher Andrew Poling Kempes.Ph.D.in Physical Biolog

Physiological and transcriptomic aspects of adaptation to extreme environments

Doctor of PhilosophyDepartment of BiologyMichael ToblerExtremophiles are organisms with the ability to survive in environments characterized by strong physicochemical stressors lethal to most other organisms, providing excellent models to further our understanding of life's capacities and limitations to deal with far-from-average conditions. I studied how physiological processes varied among fish residing in starkly different environmental conditions to understand how organisms cope with extreme environments and disentangle the roles of short-term plastic responses and evolved population differences in shaping physiological responses. I used the Poecilia mexicana model, a series of extremophile fish populations that has colonized toxic hydrogen sulfide (H₂S) rich springs and caves, to address three major objectives: (1) I investigated the energetic consequences of life in extreme environments and tested whether predicted reductions in organismal energy demands evolved repeatedly along replicated environmental gradients. (2) I characterized variation in gene expression among populations and organs to test for interactive effects between different stressors and identify potential physiological mechanisms underlying adaptation to H₂S and cave environments. (3) I conducted common garden and H₂S-exposure experiments to test how evolutionary change and plasticity interact to shape variation in gene expression observed in nature. To address these objectives, I measured variation in metabolic physiology and quantified variation in physiological processes through genome-wide gene expression analyses. I found that adaptation to extreme environments directly impacts energy metabolism, with fish living in extreme environments consistently expending less energy overall. Reductions in energy demand have evolved in convergence and were primarily mediated through a life history shift (reduction in body mass). The quantification of gene expression across divergent habitats and organs revealed organ-specific physiological responses in H₂S-rich and cave habitats. Gene expression variation in the relevant genes was primarily shaped by evolutionary change in gene regulation, and ancestral plastic responses play a minor role in causing the observed expression differences between replicated sulfidic and nonsulfidic populations in nature. Overall, my research has implications for understanding the capacities and constraints that shape life in extreme environments and aids in our understanding of modifications in physiological pathways mediating adaptation to elevated H₂S and perpetual darkness

Characterisation of cardiac structure and function in late adolescence and modification by adiposity and other cardiovascular risk factors

Cardiovascular disease remains one of the leading causes of death worldwide. However, a large proportion of research in the field focuses primarily on middle- to old- age, by which time much damage to the heart and vascular system has been incurred. The rationale for this research was to gain a clearer picture of cardiovascular health in late adolescence, prior to the onset of adulthood. In this thesis I characterise the cardiac structure and function of individuals from the ALSPAC cohort (average age 17.7 years) through analysing M-Mode, two dimensional and Doppler echocardiographic measures and haemodynamic, biochemical and anthropometric measures. Adiposity, sex and genetic predisposition are considered as key exposures which impact a range of cardiovascular outcomes. I consider the relationships of fat mass and lean mass with cardiovascular outcomes and the ways in which left ventricular mass indexation is affected by adiposity, lean mass, height and body surface area. I then discuss the roles which particular haemodynamic and biochemical biomarkers have in mediating associations between fat mass and left ventricular structural and functional outcomes. Finally I consider the influence which genes associated with body mass index have on key cardiovascular measures, including cardiac structural and functional measures. Adiposity has a direct and detrimental effect on cardiovascular health. My findings provide insights into the way in which adiposity affects the development of an adverse cardiometabolic phenotype from a comparatively young age and also have interesting implications for future research. Furthermore, they serve as another important reminder of the need for adiposity to be monitored throughout the life course

Metabolic syndrome risk and mental health: Relationship with physical activity and physical fitness in Flemish adults

Het metabool syndroom vertoont wereldwijd een hoge, stijgende prevalentie, en gaat gepaard met een verhoogd risico op cardiovasculaire aandoeningen, type II diabetes en vroegtijdige dood. Psychologische stress vormt eveneens een belangrijke publieke gezondheidsbedreiging omwille van de hoge prevalentie en de geassocieerde gezondheidsrisico’s, waaronder depressie, angststoornissen, en het metabool syndroom. Op basis van bepaalde biologische processen, zouden, naast stress, ook fysieke activiteit en fysieke fitheid, een causale rol kunnen hebben in de ontwikkeling van het metabool syndroom. Bovendien ondersteunen bepaalde theorieën mogelijke positieve effecten van fysieke activiteit op stress. De studie van de onderlinge relaties tussen fysieke activiteit, fysieke fitheid, stress en het metabool syndroom is dus een belangrijke bron van informatie voor de ontwikkeling van effectieve preventiestrategieën tegen stress en het metabool syndroom. Het voornaamste doel van deze thesis bestond eruit deze onderlinge relaties te onderzoeken in een populatie van Vlaamse volwassenen tussen 18 en 75 jaar. Voorafgaand werden echter een aantal computergestuurde psychologische vragenlijsten en een nieuw geconstrueerde continue risicoscore voor het metabool syndroom onderzocht op respectievelijk betrouwbaarheid en validiteit. De eerste studie toonde aan dat de computergestuurde versie van vijf verschillende psychologische gezondheidsvragenlijsten als een betrouwbaar alternatief voor de originele versie mag gebruikt worden in een algemene volwassen populatie. Vervolgens werd aangetoond dat een continue risicoscore van het metabool syndroom, geconstrueerd om een aantal beperkingen van reeds bestaande binaire definities op te vangen, een valide instrument is voor epidemiologisch onderzoek. In de vier relatiestudies konden we, evenwel hun cross-sectioneel karakter in het achterhoofd houdend, vooreerst besluiten dat sportparticipatie door middel van positieve effecten op sociale steun en coping, een vermindering van stress, angst en depressie kan veroorzaken. Verder kan een vermindering van sedentair gedrag resulteren in een risicoverlaging voor het metabool syndroom, supplementair op een risicoverlaging door een toename in matige tot intense fysieke activiteit. Wat betreft fysieke fitheid kan een hogere spierkracht bij vrouwen eveneens beschermend zijn tegen het metabool syndroom, bovenop een beschermend effect van een goede aerobe fitheid, terwijl bij mannen enkel een mogelijk beschermend effect van aerobe fitheid tegen het metabool syndroom werd gevonden. Tenslotte toonde een causaal model aan dat het beschermend effect van matige tot intense fysieke activiteit tegen het metabool syndroom voornamelijk zou veroorzaakt worden door een toename in fysieke fitheid