Climate change and temperature dependent biogeography: oxygen limitation of thermal tolerance in animals

Recent years have shown a rise in mean global temperatures and a shift in the geographical distribution of ectothermic animals. For a cause and effect analysis the present paper discusses those physiological processes limiting thermal tolerance. The lower heat tolerance in metazoa compared to unicellular eukaryotes and bacteria suggests that a complex systemic rather than molecular process is limiting in metazoa.Whole animal aerobic scope appears as the first process limited at low and high temperatures linked to the progressively insufficient capacity of circulation and ventilation. Oxygen levels in body fluids may decrease reflecting excessive oxygen demand at high or insufficient aerobic capacity of mitochondria at low temperatures. Aerobic scope falls at temperatures beyond the thermal optimum and vanishes at low or high critical temperatures when transition to an anaerobic mitochondrial metabolism occurs. The adjustment of mitochondrial densities on top of parallel molecular or membrane adjustments appears crucial to maintain aerobic scope and to shift thermal tolerance.In conclusion, the capacity of oxygen delivery matches full aerobic scope only within the thermal optimum. At temperatures beyond only time limited survival is supported by residual aerobic scope, then anaerobic metabolism and finally molecular protection by heat shock proteins and antioxidative defence. In a cause and effect hierarchy the progressive increase in oxygen limitation at extreme temperatures may even enhance oxidative and denaturation stress. As a corollary, capacity limitations at a complex level of organisation, the oxygen delivery system, define thermal tolerance limits before molecular functions become disturbed

Birth Order and the Intrahousehold Allocation of Time and Education

A potential determinant of intrahousehold distribution is the birth order of children. While a number of studies have analysed birth order effects in developed countries there are still only a few dealing with developing countries. This paper develops a model of intrahousehold allocation with endogenous fertility, which captures the relation between birth order and investment in children and shows that a birth order effect in intrahousehold allocation can arise even without assumptions about parental preferences for specific birth order children or genetic endowments varying by birth order. The important contribution is that fertility is treated as endogenous, something which other models of intrahousehold allocation have ignored despite the large literature on determinants of fertility. The implications of the model are that children with higher birth orders have an advantage over siblings with lower birth orders and that parents who are inequality averse will not have more than one child. The model furthermore shows that not taking account of the endogeneity of fertility when analysing intrahousehold allocation may seriously bias the results. The effects of a child’s birth order on its human capital accumulation are analysed using a longitudinal data set from the Philippines. Contrary to most longitudinal data sets this data set covers a very long period. We are, therefore, able to examine the effects of birth order on both number of hours in school during education and completed education. The results for both are consistent with the predictions of the model.

Simultaneous observations of haemolymph flow and ventilation in marine spider crabs at different temperatures: a flow weighted MRI study

In vivo magnetic resonance imaging (MRI) and angiography were applied to the marine spider crab Maja squinado for a study of temperature effects and thermal tolerance. Ventilation and haemolymph circulation were investigated during progressive cooling from 12°C to 2°C. The anatomical resolution of MR images from Maja squinado obtained with a standard spin echo sequence were suitable to resolve the structures of various internal organs. The heart of the animal could be depicted without movement artifacts. The use of a flow compensated gradient echo sequence allowed simultaneous observations of ventilation, reflected by water flow through the gill chambers as well as of haemolymph flow. Simultaneous investigation of various arteries was possible by use of flow weighted MRI. In addition to those accessible by standard invasive flow sensitive doppler sensors, flow changes in gill, leg arteries and the venous return could be observed. Both ventilation and haemolymph flow decreased during progressive cooling and changes in haemolymph flow varied between arteries. Haemolymph flow through the Arteria sternalis, some gill and leg arteries was maintained at low temperatures indicating a reduced thermal sensitivity of flow in selected vessels. In support of previous invasive studies of haemolymph flow as well as heart and ventilation rates, the results demonstrate that the operation of gills and the maintenance of locomotor activity are critical for cold tolerance. A shift in haemolymph flow between arteries likely occurs to ensure the functioning of locomotion and ventilation in the cold

Physiological capacity of Cancer setosus larvae — Adaptation to El Niño Southern Oscillation conditions

Temperature changes during ENSO challenge the fauna of the Pacific South American coast. In many ectotherm benthic species pelagic larvae are the most important dispersal stage, which may, however, be particularly vulnerable to such environmental stress. Thermal limitation in aquatic ecotherms is hypothesized to be reflected first in the aerobic scope of an animal. Here we present results on whole animal oxygen consumption and on the activities of two metabolic key enzymes, citrate synthase (CS) and pyruvate kinase (PK)) of Cancer setosus zoeal larvae, acclimated to different temperatures. Larvae acclimated to cooler temperatures (12 and 16 °C) were able to compensate for the temperature effect as reflected in elevated mass specific respiration rates (MSR) and enzyme activities. In contrast, warm acclimated larvae (20 and 22 °C) seem to have reached their upper thermal limits, which is reflected in MSR decoupling from temperature and low Q10 values (Zoea I: 1.4; Zoea III: 1.02). Thermal deactivation of CS in vitro occurred close to habitat temperature (between 20 and 24 °C), indicating instability of the enzyme close to in vivo thermal limits. The capacity of anaerobic metabolism, reflected by PK, was not influenced by temperature, but increased with instar, reflecting behavioral changes in larval life style. Functioning of the metabolic key enzyme CS was identified to be one possible key for larval limitation in temperature tolerance

The effects of changing climate on faunal depth distributions determine winners and losers

Changing climate is predicted to impact all depths of the global oceans, yet projections of range shifts in marine faunal distributions in response to changing climate seldom evaluate potential shifts in depth distribution. Marine ectotherms’ thermal tolerance is limited by their ability to maintain aerobic metabolism (oxygen- and capacity-limited tolerance), and is functionally associated with their hypoxia tolerance. Shallow-water (<200 m depth) marine invertebrates and fishes demonstrate limited tolerance of increasing hydrostatic pressure (pressure exerted by the overlying mass of water), and hyperbaric (increased pressure) tolerance is proposed to depend on the ability to maintain aerobic metabolism, too. Here, we report significant correlation between the hypoxia thresholds and the hyperbaric thresholds of taxonomic groups of shallow-water fauna, suggesting that pressure tolerance is indeed oxygen-limited. Consequently, it appears that the combined effects of temperature, pressure, and oxygen concentration constrain the fundamental ecological niches (FENs) of marine invertebrates and fishes. Including depth in a conceptual model of oxygen- and capacity-limited FENs’ responses to ocean warming and deoxygenation confirms previous predictions made based solely on consideration of the latitudinal effects of ocean warming (e.g. Cheung et al., 2009), that polar taxa are most vulnerable to the effects of climate change, with Arctic fauna experiencing the greatest FEN contraction. In contrast, the inclusion of depth in the conceptual model reveals for the first time that temperate fauna as well as tropical fauna may experience substantial FEN expansion with ocean warming and deoxygenation, rather than FEN maintenance or contraction suggested by solely considering latitudinal range shifts

Model-Based Design of Process Strategies for Cell Culture Bioprocesses: State of the Art and New Perspectives

Production processes for biopharmaceuticals with mammalian cells have to provide a nearly optimal environment to promote cell growth and product formation. Design and operation of a bioreactor are complex tasks, not only with respect to reactor configuration and size but also with respect to the mode of operation. New concepts for the design and layout of process strategies are required to meet regulatory demands and to guarantee efficient, safe, and reproducible biopharmaceutical production. Key elements are critical process parameters (CPPs), which affect critical quality attributes (CQAs), quality by design (QbD), process analytical tools (PAT), and design of experiment (DoE). In this chapter, some fundamentals including process and control strategies as well as concepts for process development are discussed. Examples for novel model-based concepts for the design of experiments to identify suitable fed-batch-feeding strategies are shown