To understand the role of the seed coat in regulation of houndstongue seed dormancy, the effects of manipulation of seed coat integrity on seed germination and O2 uptake were studied. The results suggest that the seed coat of this weed regulates dormancy in part by interfering with the diffusion of O2 to the embryo. Scanning electron microscopy showed a network of ridges on the seed coat surface that were partially dissolved following 1.5 min of sulphuric acid scarification. Mechanical scarification removed fragments of the seed coat surface. Both scarification treatments stimulated seed germination. Supply of an elevated level of O2 also stimulated seed germination. O2 uptake by seeds imbibed in O2-saturated water was 150% higher than that for seeds imbibed in air-saturated water. Although all treatments that stimulated seed germination also stimulated O2 uptake, there was a lack of a consistent, quantitative relationship between increases in O2 uptake and seed germination in various experiments. This suggests that limitation of O2 availability to the embryo is not the only factor involved in regulation of houndstongue seed dormancy by the seed coat. Mechanical restriction of embryo expansion by the seed coat may also be important. Methanol-insoluble phenolics constituted < 1% of the total phenolic pool in the embryo. Their potential oxidation could not account for more than a small fraction of the previously reported massive stimulation of O2 uptake by the embryo upon decoating. The present O2 uptake and seed germination studies indicate that not all of the large increase in O2 uptake following decoating is essential for houndstongue seed germination.

An appropriate energy feeding management that ensures the optimal dietary energy supply according to the energy expenditure (EE) is a crucial component for the horse’s performance. The main purpose of this study was to determine the EE during four specific exercises used in the training of Standardbred trotters (promenade, jogging, parcours and interval work-outs). A total of six Standardbred geldings performed four different testing situations on a track. The intensity (expressed in percentage of the maximal velocity over 500 m, i.e. v500) and volume (distance and duration) of the testing situations were determined according to practices reported by French trainers. Promenade and jogging included only an exercise phase, whereas parcours and interval situations also included a warm-up and a recovery phase. Oxygen uptake (VO2), carbon dioxide production (VCO2) and heart rate (HR) were continuously recorded from 2 min before the beginning through to the end of the testing situations, using a portable respiratory gas analyser. Blood lactate levels and rectal temperature were determined before and immediately after the exercise phase of each testing situations. EE of the different phases (warm-up, exercise and recovery) and EE of the entire testing situations (EETOTAL) were calculated from VO2 measurements and the O2 caloric equivalent. Interval and parcours situations induced higher physiological responses than promenade and jogging situations, particularly in terms of VO2peak, VCO2peak and HRpeak. The highest blood lactate concentration (6 mmol/l) was measured after the interval exercise, and respiratory exchange ratios ⩾1 were observed only for the parcours situation. The EE of exercise phase varied from 0.49 to 1.79 kJ/min per kg for promenade and parcours situations. The EE of warm-up and recovery phases did not differ between parcours and interval situations, and was estimated at 1.04 and 0.57 kJ/min per kg BW, respectively. On average, the warm-up and the recovery phases contributed to 38% and 19% of the EETOTAL. For promenade, jogging, parcours and interval situations, EETOTAL was evaluated at 12 618, 11 119, 13 698 and 18 119 kJ, respectively.

The effect of short-term (5 days) exposure to CO2-acidified seawater (year 2100 predicted values, ocean pH = 7.6) on key aspects of the function of the intertidal common limpet Patella vulgata (Gastropoda: Patellidae) was investigated. Changes in extracellular acid–base balance were almost completely compensated by an increase in bicarbonate ions. A concomitant increase in haemolymph Ca2+ and visible shell dissolution implicated passive shell dissolution as the bicarbonate source. Analysis of the radula using SEM revealed that individuals from the hypercapnic treatment showed an increase in the number of damaged teeth and the extent to which such teeth were damaged compared with controls. As radula teeth are composed mainly of chitin, acid dissolution seems unlikely, and so the proximate cause of damage is unknown. There was no hypercapnia-related change in metabolism (O2 uptake) or feeding rate, also discounting the possibility that teeth damage was a result of a CO2-related increase in grazing. We conclude that although the limpet appears to have the physiological capacity to maintain its extracellular acid–base balance, metabolism and feeding rate over a 5 days exposure to acidified seawater, radular damage somehow incurred during this time could still compromise feeding in the longer term, in turn decreasing the top-down ecosystem control that P. vulgata exerts over rocky shore environments.

A novel technique allows long-term monitoring of real-time oxygen consumption during seed germination in an open system. Most current techniques used to detect oxygen consumption by seeds measure the decrease in oxygen concentration in a closed chamber. This is not ideal for long-term experiments because the chamber must be replenished with air periodically, subjecting the seeds to abrupt changes in oxygen concentration. The current technique employs an open system, in which seeds are submerged in a continuously aerated aqueous environment. Oxygen electrodes are used to measure the steady-state concentration of oxygen in the solution, which is a function of both the rate of oxygen consumption by the seed and the rate of aeration from the atmosphere. The rate of aeration is directly dependent on the oxygen concentration of the bathing solution; therefore, previous calibration of the system allows the direct conversion of steady-state oxygen concentrations into oxygen consumption rates. Because oxygen is not limiting, the experimental design described here can monitor the same sample non-intrusively every minute for more than 24 h, allowing for greater precision than hourly readings often reported with current techniques. Multiple treatments and/or replicates can be run simultaneously, allowing sensitive comparison of various seed treatments or seed types. To illustrate its potential application, the technique was used to follow the rehydration and pre-emergence phases of germination of cucumber (Cucumis sativum), pea (Pisum sativum) and mustard (Brassica juncea) seeds, detect the inhibitory effects of surface sterilization techniques on seed respiration of cucumber, and follow the interaction of a bacterial biocontrol agent with germinating cucumber and pea seeds.

Reasons for performing the study: In human exercise physiology, the current gold standard for evaluating aerobic capacity is the measurement of oxygen consumption (VO2) and maximal oxygen uptake (VO2max). The evaluation of VO2 in horses is performed in some laboratories equipped with a treadmill but has only been exceptionally reported in field conditions because of the lack of adapted equipment. Objectives: The aim of this study was (1) to assess the feasibility of VO2 measurement on the track using a recently validated portable breath-by-breath gas analyser system adapted to horses (Cosmed K4b2® and Equimask®), (2) to compare these results with those obtained during a treadmill exercise test and (3) to study correlations between VO2 and physiological parameters usually measured in field condition such as heart rate (HR), lactataemia (LA) and the speed at which HR equals 200 beats per minute (bpm) (V200) or LA 4 mmol l− 1 (VLA4). Methods: Five healthy Standardbred trotters in training were submitted to two stepwise incremental exercise tests, one driven on the racetrack and the other on a high-speed treadmill with a 4% incline. Speed (v), HR, ventilatory parameters and VO2 were continuously recorded throughout the duration of the tests and LA was evaluated after each step. Results: All horses completed the test satisfactorily after an initial acclimatization to the mask. There were marked individual differences in ventilatory strategy, and breathing frequency (Rf) at the higher levels of exercise was noticeably low. The VCO2 measurements were incoherent. There were no significant differences between track and treadmill maximal data obtained during the last step [VO2peak (track: 139.9 ± 8.9 ml kg− 1 min− 1; treadmill: 139.9 ± 13.4 ml kg− 1 min− 1), LAmax (track: 6.5 ± 1.6 mmol l− 1; treadmill: 7.3 ± 3.0 mmol l− 1), HRmax (track: 229 ± 6.2 bpm; treadmill: 222 ± 13 bpm)], although the maximal speed required to reach similar workloads was significantly higher on the track (11.9 ± 0.6 m s− 1vs. 9.7 ± 0.4 m s− 1). The correlation between VO2 and HR (r = 0.87; P < 0.001) and VO2 and LA (r = 0.75; P < 0.0001) during both tests was good but no correlation was found between VO2peak and HRmax, LAmax, V200 or VLA4. Conclusions: This is the first report of a practical portable system to measure VO2 and ventilation continuously during high-speed field exercise tests. However, current mask design markedly influences ventilation and could have prohibited the attainment of VO2max. Furthermore, consistent VCO2 measurements should be implemented by the manufacturers. Potential relevance: Continuous breath-by-breath ventilation and VO2 measurements can be recorded in horses in the field at submaximal levels. With necessary adaptations to the system entailed, this study opens new perspectives in the analysis of physiological and metabolic mechanisms of exercise in the equine species in genuine track conditions.

Although toxic for early stages of embryo development, glucose is a physiological metabolic substrate at the morula and blastocyst stages. We evaluated the effect of adding 5.5 mM glucose from the morula stage on bovine blastocyst development and quality. In vitro matured and fertilised bovine oocytes were cultured in modified Synthetic Oviduct Fluid medium containing 5% fetal calf serum, but without added glucose, up to day 5 post-insemination (pi). Morulae were selected and further cultured in the presence or absence of 5.5 mM glucose. Blastocyst and hatched blastocyst rates were recorded. Oxygen, glucose and pyruvate uptakes as well as lactate release were evaluated. The quality of the resulting blastocysts was evaluated by the cell allocation to the inner cell mass (ICM) and trophectoderm (TE) and by the apoptotic index. Adding glucose increased the blastocyst rate at day 8 pi (80% vs 65%) but had no impact on hatching rate (25% vs 28%). A 22% decrease in oxygen uptake was observed in the presence of glucose, concomitant with an increase in lactate release, although no change was observed in pyruvate uptake. A slight decrease in blastocyst cell number was observed at day 7 in the presence of glucose while neither the ICM/TE cell ratio nor the apoptotic index were affected. In conclusion, adding 5.5 mM glucose from the morula stage has a limited impact on blastocyst rate and quality although important modifications were observed in embryo metabolism. It remains to be determined whether those modifications could influence embryo viability after transfer.

The relationships between macro-ecological patterns and physiological investigations in insects, especially those dealing with respiratory metabolism, are assessed in an attempt to encourage the development of the interaction between macroecology and physiological ecology. First, we demonstrate that although physiological ecology has been explicitly concerned with a number of issues relating to species boundaries, many questions remain unanswered. We argue that there are essentially two ways in which the relationship between physiological tolerances and species range boundaries have been investigated. The correlational approach involves physiological inference, physiological prediction, isocline analyses and climatic matching, and has often been criticized for a lack of rigour, while the experimental approach seeks to examine experimentally the relationships between physiological variables and range edges. Second, we use the recent debate on processes underlying latitudinal patterns in body size to caution against the conflation of patterns and processes operating at intraspecific and interspecific levels, the dangers inherent in invoking single explanatory variables, and an undue focus on adaptationist (e.g. optimization) rather than non-adaptationist explanations or some combination of the two. We show that both positive and negative relationships between body size and latitude have been found at the intraspecific level and suggest that interactions between temperature-induced heterochrony, and the relationship between habitat durational stability, growing season length, and generation time can be used to explain these differences. Similar variation in documented patterns is demonstrated at the interspecific level, and the mechanisms usually proffered to explain such clines (especially the starvation/desiccation-resistance hypothesis) are discussed. Interactions between various environmental factors, such as host-plant quality, and their effects on size clines are also discussed. Third, we argue that respiratory metabolism, as a measure of ATP cost, and its spatio-temporal variation are critical to many explanations of macroecological patterns. Adaptive changes in metabolism reputedly involve both depression (stress resistance) and elevation of metabolic rate, although recent studies are increasingly calling these ideas into question. In particular, flow-through respirometry is revolutionizing results by allowing careful separation of resting (or standard) and active metabolic rates. These techniques have rarely been applied to studies of metabolic cold adaptation in insects, one of the most polemical adaptations ascribed to high-latitude and high-altitude species. We conclude by arguing that physiological investigations of species tolerances are important in the context of macroecology, especially species distributional patterns and the possible impact of climate change thereon. However, we caution that relationships between abiotic variables, species tolerances, and distributional ranges may be non-linear and subject to considerable modification by the presence of other species, and that many of the pressing questions posed by macroecology have not been addressed by insect physiologists. Nonetheless, we suggest that because an understanding of the dynamics of species distributions is of considerable importance, especially in the context of current conservation problems, insect physiological ecology has much future scope.

The effect of feeding v. fasting, on tissue blood flow, oxygen uptake and proportional contributions of the portal drained viscera (PDV), liver (Expts 1 and 2) and hindquarters (HQ; Expt 2) to whole-body O2 uptake were studied in beef steers. The combined techniques of indirect calorimetry and net tissue flux, the latter being the product of arterio-venous concentration difference and blood flow, were used in the experiments. In response to fasting, whole-body O2 consumption decreased as did O2 uptake by all measured tissues except the liver (trend only in Expt 1). Blood flow to all measured tissues decreased during fasting and fractional uptake of O2 decreased in PDV and increased in liver and HQ (Expt 2). Proportional contribution of specific tissues to whole-body O2 uptake changed when animals were switched from the fed to the fasted state. The percentage consumed by PDV decreased from 25.4 to 19.9, by liver increased from 20.5 to 26.4 and by HQ was unchanged (9.6 and 10.5) in Expt 2. These significant responses in Expt 2 were observed as trends in Expt 1. The changes in proportional contribution of tissues to whole-animal O2 uptake reflect the changing metabolic role of specific tissues to lack of food supply. These findings emphasize the central role of the liver in metabolism and indicate that fasting (catabolic) measurements may not reflect the previous fed (anabolic) physiological state.

Ash-free-dry-weight determinations for a representative range of living brachiopod genera have revealed that a consistently high proportion of total organic mass is contained within the shell, partly as the organic matrix for biomineralisation and partly as minute extensions of the mantle tissues (caeca) housed within hollow endopunctae permeating the shell. On average 40% to 50% of the total organic mass of both articulate and inarticulate brachiopods is situated within the shell. This is true even for a rhynchonellid brachiopod which does not possess endopunctae, but which has a more dense protein matrix in its shell. The effectively hidden constituent of brachiopod tissue mass which is included in this component has often been overlooked, and as a result total metabolic tissue mass has been underestimated. This throws into question some previous interpretations of brachiopod respiratory and metabolic data.

The oxygen consumption rates of several living brachiopods have been measured, and when respiring tissue in caeca in the shell is taken into consideration, it is clear that brachiopod metabolic rates are low when compared with other marine invertebrates (e.g. between 10% and 50% of the oxygen uptake of comparable gastropods and bivalve molluscs held in similar conditions). This low rate cannot be attributed to a slower pumping rate by the brachiopod lophophore, as has been suggested, because the rate of water movement is comparable to that across the bivalve gill.

Nitrogen excretion rates have also been measured for a few living brachiopods, allowing a comparison with rates of oxygen consumption and providing an indication of the metabolic substrates used. These data on oxygen: nitrogen ratios suggest that one Antarctic brachiopod utilises exclusively protein as a metabolic substrate, while a temperate latitude species uses mainly protein during winter but lipids and carbohydrates during summer months. Histological observations, particularly of Terebratulina retusa from temperate waters, show that a specialised tissue layer in the brachiopod outer mantle epithelium proximal to the shell may be the site of storage of the protein that is metabolised during winter, and of carbohydrate mobilised during gonadal development in summer. The caeca have also been suggested as sites of storage of metabolites, and the possible relationships between these areas of mantle are discussed. It seems that the ability to store nutrients in the mantle, combined with flexibility of substrate utilisation and an inherently low metabolic rate, have been important factors in brachiopod evolution.