Lower Metabolic Efficiency Research Articles

A metabolic perspective on polyploid invasion and the emergence of life histories: Insights from a mechanistic model.

Whole-genome duplication (WGD, polyploidization) has been identified as a driver of genetic and phenotypic novelty, having pervasive consequences for the evolution of lineages. While polyploids are widespread, especially among plants, the long-term establishment of polyploids is exceedingly rare. Genome doubling commonly results in increased cell sizes and metabolic expenses, which may be sufficient to modulate polyploid establishment in environments where their diploid ancestors thrive. We developed a mechanistic simulation model of photosynthetic individuals to test whether changes in size and metabolic efficiency allow autopolyploids to coexist with, or even invade, ancestral diploid populations. Central to the model is metabolic efficiency, which determines how energy obtained from size-dependent photosynthetic production is allocated to basal metabolism as opposed to somatic and reproductive growth. We expected neopolyploids to establish successfully if they have equal or higher metabolic efficiency as diploids or to adapt their life history to offset metabolic inefficiency. Polyploid invasion was observed across a wide range of metabolic efficiency differences between polyploids and diploids. Polyploids became established in diploid populations even when they had a lower metabolic efficiency, which was facilitated by recurrent formation. Competition for nutrients is a major driver of population dynamics in this model. Perenniality did not qualitatively affect the relative metabolic efficiency from which tetraploids tended to establish. Feedback between size-dependent metabolism and energy allocation generated size and age differences between plants with different ploidies. We demonstrated that even small changes in metabolic efficiency are sufficient for the establishment of polyploids.

Serial adaptive laboratory evolution enhances mixed carbon metabolic capacity of Escherichia coli

Microbes have inherent capacities for utilizing various carbon sources, however they often exhibit sub-par fitness due to low metabolic efficiency. To test whether a bacterial strain can optimally utilize multiple carbon sources, Escherichia coli was serially evolved in L-lactate and glycerol. This yielded two end-point strains that evolved first in L-lactate then in glycerol, and vice versa. The end-point strains displayed a universal growth advantage on single and a mixture of adaptive carbon sources, enabled by a concerted action of carbon source-specialists and generalist mutants. The combination of just four variants of glpK, ppsA, ydcI, and rph-pyrE, accounted for more than 80% of end-point strain fitness. In addition, machine learning analysis revealed a coordinated activity of transcriptional regulators imparting condition-specific regulation of gene expression. The effectiveness of the serial adaptive laboratory evolution (ALE) scheme in bioproduction applications was assessed under single and mixed-carbon culture conditions, in which serial ALE strain exhibited superior productivity of acetoin compared to ancestral strains. Together, systems-level analysis elucidated the molecular basis of serial evolution, which hold potential utility in bioproduction applications.

Day‐night variation of microbial organic matter use in sediments of a saline shallow lake

Abstract Knowledge of microbial functioning linked to dissolved organic matter (DOM) in hypersaline lakes is limited. This study aimed to understand this relationship in surface and subsurface sediments and how it is affected by daytime and night‐time variability. A sampling regime, including daytime and night‐time measurements, was designed to record aerobic respiration, extracellular enzyme activity (β‐glucosidase, leu‐aminopeptidase and phosphatase), prokaryotic cell density and viability, content of pigment and extracellular polymeric substances (EPS), and organic matter weight in the surface and subsurface sediments. The main physicochemical characteristics and optical properties of DOM in the surface and interstitial waters were determined. Larger differences were detected in biofilm microbial activity between surface and subsurface sediments than between day and night, as a result of higher prokaryotic cell density and higher availability of fresh DOM at the surface, possibly released from primary production. Redox conditions, pH and DOM quantity and quality were strongly correlated with enzyme activity and variability in respiration, and might determine (through modifying nitrogen (N) and phosphorus (P) availability) how microbes use organic compounds differently at the two sediment depths. Low prokaryotic viability indicated that the microbial community was stressed in both surface and subsurface sediments. By contrast, higher EPS and pigment content and lower metabolic efficiency at the surface layer indicated harsher conditions compared to the subsurface layer. Pigment presence and variation in daily oxygen levels in the subsurface layer indicate that the two sediment depths are interconnected. Results suggest that surface and subsurface microbes have a distinct role in hypersaline shallow lake sediment. Microorganisms in surface sediments form a structured mat with high EPS and carotenoids and enhanced carbon metabolism. The mat also serves as a protection shield from light radiation, salinity and desiccation. At the subsurface, the lower availability of fresh organic compounds and oxygen reduces microbial biomass and activity which is, in turn, more efficient and focused on N and P acquisition.

Rural system sustainability evaluation based on emergy analysis: An empirical study of 321 villages in China

The deterioration of the rural ecosystem, the poverty of population, and the low well-being of farmers have brought great challenges to the realization of the Sustainable Development Goals (SDGs). Assessing the current situation of rural sustainable development and identifying limiting factors are critical to sustainable development of rural areas. This study evaluates rural sustainability of 321 villages in China based on emergy analysis. Then, random forest has been employed to determine the limiting factors of villages with different sustainable development levels. The results show that the current level of sustainable development in Chinese rural areas is relatively low (from 0.0040 to 9.5468), showing the trend of gradual increase in rural sustainability from the east to the west. There is a trade-off relationship between social-economic development and the ecological environment, resulting from only 32% of villages are high Emergy Yield Rate and low Environmental Loading Ratio. High-sustainability villages are rich in natural resources and higher metabolic efficiency but poor in people's living, indicating that the natural capital needs to be excavated to improve economic levels and social well-being in the future. Low-sustainability villages have better human well-being due to faster economic development, but unbalanced external inputs and outputs result in low metabolic efficiency and high environmental pressure. Precipitation, agricultural materials input, and people living consumption are the main driving factors for rural sustainability. It is suggested to introduce effective policies to increase economic measures and human well-being for high-sustainability villages, and appropriately decrease external purchasing such as fertilizer and pesticides for low-sustainability villages to make progress in rural sustainable development and Chinese Rural Revitalization.

Use of blood and its components in the treatment of anaemia in children

AbstractBlood transfusion is a well-established treatment for anaemia. Herein, blood and its components are transfused to replenish circulating blood volume, maintain the oxygen capacity of the blood and normalise the function of the coagulation system. Anaemia treatment by blood transfusions is a great challenge, especially with reference to paediatric patients. Blood is irreplaceable in a life-threatening situation, but it has its own side effects, just like all applied pharmacological products. Hence, it is extremely important to carefully select donors and utilise blood components according to the patient’s individual needs. Children represent a group that requires specific criteria to be met, mainly because of the fact that their physiological and haematological systems differ from those of adults. The most common types of anaemia seen in children are deficiency anaemias such as iron-deficiency anaemia, while less common are vitamin B12 deficiency anaemia or folate deficiency anaemia. Secondary anaemia is also relatively frequent in chronic diseases, among others, immunological or infectious, as well as renal, liver, endocrine and neoplastic diseases. Anaemia due to blood loss is also included in this group. Furthermore, some anaemias, such as aplastic anaemia (due to impaired erythrocyte production) and haemolytic anaemia (due to excessive destruction of red blood cells) may be congenital or acquired. Before deciding to implement blood therapy, the patient’s clinical condition or the different haematological, biochemical and immunological parameters at different stages of life should be considered. Since each transfusion may result in a variety of post-transfusion reactions, immunisation or transmission of infectious diseases, the decision to transfuse blood or blood components should be taken only when the patient cannot be treated effectively by any other means and the expected benefits of the transfusion outweigh the risks associated with possible complications. Considering the recipients’ low blood volume, low metabolic efficiency, higher haematocrit levels than in adults and immature immune system, products for these patients should be prepared in a special way. These components must ensure minimal risk of metabolic and haemostatic disorders. The collection of these products, as well as their preparation, storage and transfusion, should be carried out in accordance with current legislation.

Periprostatic Adipose Tissue Thromboinflammation Drives Early Prostatic Neoplastic Alterations in a Rat Model of Mild Metabolic Dysfunction

Emerging evidence links periprostatic adipose tissue (PPAT) inflammation, a consequence of metabolic impairment, and certain features of prostate cancer (PCa) aggressiveness. AT thromboinflammation, mediated by the proteolytic activation of protease‐activated receptors (PARs) particularly by thrombin and Factor Xa (FXa), drives AT dysfunction. Nevertheless, the contribution of PPAT thromboinflammation to early prostatic neoplastic alterations has not been investigated. Here, we utilized a non‐obese prediabetic rat model to assess prostatic neoplasia in association with PPAT thromboinflammation. Mild hypercaloric diet (MHC)‐fed rats exhibited hyperinsulinemia, hypertriglyceridemia, a lower metabolic efficiency, and a higher fat/lean ratio in comparison to regular chow‐fed rats. When compared to regular chow‐fed rats, MHC‐fed rats exhibited PPAT with larger adipocytes, enhanced oxidative stress and increased immune cell influx. Concurrently, prostates from MHC‐fed rats displayed higher number of prostatic intraepithelial neoplasia (PIN), enhanced expression of the proliferation markers Ki67 and PCNA, enhanced expression of cytokeratin 8 (CK8), pronounced fibrosis and increased immune cell influx. Further profiling of macrophage polarization in PPAT and the prostate is underway. Importantly, these prostatic and adipocytic manifestations were attenuated in MHC‐fed rats treated with non‐hemorrhagic doses of rivaroxaban, a direct FXa inhibitor. Ongoing in vitro investigation demonstrates that rivaroxaban reduces the migratory potential of murine prostate cancer cells (Plum‐AD); and the effect of rivaroxaban on the colony forming and sphere forming capacities of Plum‐AD cells are being studied. Further investigation is ongoing to delineate the molecular underpinnings of rivaroxaban‐associated amelioration of PPAT inflammation and the associated prostatic neoplastic alterations.

Biological Network Approach for the Identification of Regulatory Long Non-Coding RNAs Associated With Metabolic Efficiency in Cattle.

Background: Genomic regions associated with divergent livestock feed efficiency have been found predominantly outside protein coding sequences. Long non-coding RNAs (lncRNA) can modulate chromatin accessibility, gene expression and act as important metabolic regulators in mammals. By integrating phenotypic, transcriptomic, and metabolomic data with quantitative trait locus data in prioritizing co-expression network analyses, we aimed to identify and functionally characterize lncRNAs with a potential key regulatory role in metabolic efficiency in cattle.Materials and Methods: Crossbred animals (n = 48) of a Charolais x Holstein F2-population were allocated to groups of high or low metabolic efficiency based on residual feed intake in bulls, energy corrected milk in cows and intramuscular fat content in both genders. Tissue samples from jejunum, liver, skeletal muscle and rumen were subjected to global transcriptomic analysis via stranded total RNA sequencing (RNAseq) and blood plasma samples were used for profiling of 640 metabolites. To identify lncRNAs within the indicated tissues, a project-specific transcriptome annotation was established. Subsequently, novel transcripts were categorized for potential lncRNA status, yielding a total of 7,646 predicted lncRNA transcripts belonging to 3,287 loci. A regulatory impact factor approach highlighted 92, 55, 35, and 73 lncRNAs in jejunum, liver, muscle, and rumen, respectively. Their ensuing high regulatory impact factor scores indicated a potential regulatory key function in a gene set comprising loci displaying differential expression, tissue specificity and loci overlapping with quantitative trait locus regions for residual feed intake or milk production. These were subjected to a partial correlation and information theory analysis with the prioritized gene set.Results and Conclusions: Independent, significant and group-specific correlations (|r| > 0.8) were used to build a network for the high and the low metabolic efficiency group resulting in 1,522 and 1,732 nodes, respectively. Eight lncRNAs displayed a particularly high connectivity (>100 nodes). Metabolites and genes from the partial correlation and information theory networks, which each correlated significantly with the respective lncRNA, were included in an enrichment analysis indicating distinct affected pathways for the eight lncRNAs. LncRNAs associated with metabolic efficiency were classified to be functionally involved in hepatic amino acid metabolism and protein synthesis and in calcium signaling and neuronal nitric oxide synthase signaling in skeletal muscle cells.

Thermodynamic Modeling of the Competition Between Cancer and Normal Cells

AbstractOne of the recognized differences between normal and cancer cells is in their metabolic profile. Tumor cells tend to produce energy through glycolysis rather than the much more efficient oxidative phosphorylation pathway, which healthy cells generally prefer. This phenomenon is identified as the Warburg effect. Although several functional explanations have been proposed for the Warburg effect, the competitive advantage of it is still subject of debate. Here we present a thermodynamic model to simulate the competition of cancer and normal cells in terms of bioenergetics. Our model shows that the Warburg effect has an advantage because the entropy production rate is increased and metabolic efficiency is decreased for cancer cells. Although inefficiency is generally considered a competitive disadvantage for living organisms, the thermodynamic model shows that it is not always the case. Indeed, when the energy resources are abundant and the system has a limited ability to export entropy, the organism with a higher rate of entropy production will have a higher chance of survival despite its lower metabolic efficiency. This thermodynamic model predicts that as long as there are enough nutrients in circulating blood, there are two thermodynamic strategies to control cancer cell populations, i. e., (i) decreasing the entropy production rate of cancer cells and (ii) increasing normal cells’ entropy production rate.

Improving the production of 22-hydroxy-23,24-bisnorchol-4-ene-3-one from sterols in Mycobacterium neoaurum by increasing cell permeability and modifying multiple genes

BackgroundThe strategy of modifying the sterol catabolism pathway in mycobacteria has been adopted to produce steroidal pharmaceutical intermediates, such as 22-hydroxy-23,24-bisnorchol-4-ene-3-one (4-HBC), which is used to synthesize various steroids in the industry. However, the productivity is not desirable due to some inherent problems, including the unsatisfactory uptake rate and the low metabolic efficiency of sterols. The compact cell envelope of mycobacteria is a main barrier for the uptake of sterols. In this study, a combined strategy of improving the cell envelope permeability as well as the intracellular sterol metabolism efficiency was investigated to increase the productivity of 4-HBC.ResultsMmpL3, encoding a transmembrane transporter of trehalose monomycolate, is an important gene influencing the assembly of mycobacterial cell envelope. The disruption of mmpL3 in Mycobacterium neoaurum ATCC 25795 significantly enhanced the cell permeability by 23.4% and the consumption capacity of sterols by 15.6%. Therefore, the inactivation of mmpL3 was performed in a 4-HBC-producing strain derived from the wild type M. neoaurum and the 4-HBC production in the engineered strain was increased by 24.7%. Subsequently, to enhance the metabolic efficiency of sterols, four key genes, choM1, choM2, cyp125, and fadA5, involved in the sterol conversion pathway were individually overexpressed in the engineered mmpL3-deficient strain. The production of 4-HBC displayed the increases of 18.5, 8.9, 14.5, and 12.1%, respectively. Then, the more efficient genes (choM1, cyp125, and fadA5) were co-overexpressed in the engineered mmpL3-deficient strain, and the productivity of 4-HBC was ultimately increased by 20.3% (0.0633 g/L/h, 7.59 g/L 4-HBC from 20 g/L phytosterol) compared with its original productivity (0.0526 g/L/h, 6.31 g/L 4-HBC from 20 g/L phytosterol) in an industrial resting cell bio-transformation system.ConclusionsIncreasing cell permeability combined with the co-overexpression of the key genes (cyp125, choM1, and fadA5) involved in the conversion pathway of sterol to 4-HBC was effective to enhance the productivity of 4-HBC. The strategy might also be useful for the conversion of sterol to other steroidal intermediates by mycobacteria.

Feed conversion efficiency in dairy cows: Repeatability, variation in digestion and metabolism of energy and nitrogen, and ruminal methanogens

The objective was to study repeatability and sources of variation in feed conversion efficiency [FCE, milk kg/kg dry matter intake (DMI)] of lactating cows in mid to late lactation. Trials 1 and 2 used 16 cows (106 to 368d in milk) grouped in 8 pairs of 1 high- and 1 low-FCE cow less than 16d in milk apart. Trial 1 determined the repeatability of FCE during a 12-wk period. Trial 2 quantified the digestive and metabolic partitioning of energy and N with a 3-d total fecal and urine collection and measurement of CH4 and CO2 emission. Trial 3 studied selected ruminal methanogens in 2 pairs of cows fitted with rumen cannulas. Cows received a single diet including 28% corn silage, 27% alfalfa silage, 17% crude protein, and 28% neutral detergent fiber (dry matter basis). In trial 1, mean FCE remained repeatedly different and averaged 1.83 and 1.03 for high- and low-FCE cows, respectively. In trial 2, high-FCE cows consumed 21% more DMI, produced 98% more fat- and protein-corrected milk, excreted 42% less manure per kilogram of fat- and protein-corrected milk, but emitted the same daily amount of CH4 and CO2 compared with low-FCE cows. Percentage of gross energy intake lost in feces was higher (28.6 vs. 25.9%), but urinary (2.76 vs. 3.40%) and CH4 (5.23 vs. 6.99%) losses were lower in high- than low-FCE cows. Furthermore, high-FCE cows partitioned 15% more of gross energy intake toward net energy for maintenance, body gain, and lactation (37.5 vs. 32.6%) than low-FCE cows. Lower metabolic efficiency and greater heat loss in low-FCE cows might have been associated in part with greater energy demand for immune function related to subclinical mastitis, as somatic cell count was 3.8 fold greater in low- than high-FCE cows. As a percentage of N intake, high-FCE cows tended to have greater fecal N (32.4 vs. 30.3%) and had lower urinary N (32.2 vs. 41.7%) and greater milk N (30.3 vs. 19.1%) than low-FCE cows. In trial 3, Methanobrevibacter spp. strain AbM4 was less prevalent in ruminal content of high-FCE cows, which emitted less CH4 per unit of DMI and per unit of neutral detergent fiber digested than low-FCE cows. Thus lower digestive efficiency was more than compensated by greater metabolic efficiencies in high- compared with low-FCE cows. There was not a single factor, but rather a series of mechanisms involved in the observed differences in efficiency of energy utilization of the lactating cows in this study.

Refeeding after acute food restriction: Differential reduction in preference for ethanol and ethanol-paired flavors in selectively bred rats

Rats' voluntary ethanol intake varies with dispositional factors and energy status. The joint influences of these were of interest here. We previously reported that rats selectively bred for high voluntary saccharin intake (HiS) consume more ethanol and express more robust conditioning of preference for flavors paired with voluntarily consumed ethanol than do low-saccharin consuming counterparts (LoS). Three new experiments examined the effect of refeeding after an episode of food restriction on ethanol intake and on preference for ethanol-paired flavors in HiS and LoS rats. A 48-h episode of food restriction with wheel running reduced intake of and preference for 4% ethanol (Exp. 1a) and preference for an ethanol-paired flavor (Exp. 1b) during refeeding. Food restriction alone was sufficient to reduce the flavor preference (Exp. 2). Adding fat to the refeeding diet or extending the food restriction period exacerbated the effect (Exp. 3), yielding a frank aversion to ethanol-paired flavors in LoS rats. These studies indicate that rebound from negative energy balance shifts responses to ethanol-associated cues from preference toward aversion. Analyses of bodyweight changes and caloric intake during refeeding support this conclusion and further suggest that lower metabolic efficiency may be a marker for enhanced preference mutability.

Na+ Recirculation and Isosmotic Transport

The Na(+) recirculation theory for solute-coupled fluid absorption is an expansion of the local osmosis concept introduced by Curran and analyzed by Diamond & Bossert. Based on studies on small intestine the theory assumes that the observed recirculation of Na(+) serves regulation of the osmolarity of the absorbate. Mathematical modeling reproducing bioelectric and hydrosmotic properties of small intestine and proximal tubule, respectively, predicts a significant range of observations such as isosmotic transport, hyposmotic transport, solvent drag, anomalous solvent drag, the residual hydraulic permeability in proximal tubule of AQP1 (-/-) mice, and the inverse relationship between hydraulic permeability and the concentration difference needed to reverse transepithelial water flow. The model reproduces the volume responses of cells and lateral intercellular space (lis) following replacement of luminal NaCl by sucrose as well as the linear dependence of volume absorption on luminal NaCl concentration. Analysis of solvent drag on Na(+) in tight junctions provides explanation for the surprisingly high metabolic efficiency of Na(+) reabsorption. The model predicts and explains low metabolic efficiency in diluted external baths. Hyperosmolarity of lis is governed by the hydraulic permeability of the apical plasma membrane and tight junction with 6-7 mOsm in small intestine and < or = 1 mOsm in proximal tubule. Truly isosmotic transport demands a Na(+) recirculation of 50-70% in small intestine but might be barely measurable in proximal tubule. The model fails to reproduce a certain type of observations: The reduced volume absorption at transepithelial osmotic equilibrium in AQP1 knockout mice, and the stimulated water absorption by gallbladder in diluted external solutions. Thus, it indicates cellular regulation of apical Na(+) uptake, which is not included in the mathematical treatment.

Reduced Adiposity in Bitter Melon (Momordica charantia)–Fed Rats Is Associated with Increased Lipid Oxidative Enzyme Activities and Uncoupling Protein Expression

To further explore the antiobesity effect of freeze-dried bitter melon (BM) juice, activities of mitochondrial lipid oxidative enzymes as well as the expression of uncoupling proteins and their transcription coactivator peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1alpha) were determined in diet-induced obese (DIO) rats. Rats were fed high-fat (HF) diets to induce obesity, and the effect of BM was assessed at doses of 0.75, 1.0, or 1.25% (wt:wt). In a dose-response experiment, BM-supplemented rats had lower energy efficiency (g weight gained/kJ consumed), visceral fat mass, serum glucose, and insulin resistance index, but higher plasma norepinephrine than unsupplemented rats (P < 0.05). Hepatic and skeletal muscle triglyceride concentrations were lower in supplemented HF diet-fed rats than in unsupplemented HF diet-fed rats (P < 0.05). An HF diet supplemented with BM elevated activities of hepatic and muscle mitochondrial carnitine palmitoyl transferase-I (CPT-I) and acyl-CoA dehydrogenase (AD) (P < 0.05). In another experiment, BM (1.0 g/100 g) lowered visceral fat mass but increased serum adiponectin concentration in HF diet-fed rats (P < 0.05). In the final study, rats were fed the HF diet with 0, 1.0 or 1.25% BM. Both groups of BM-supplemented rats had higher uncoupling protein 1 in brown adipose tissue (P < 0.05) and uncoupling protein 3 in red gastrocnemius muscle (P < 0.05), measured by Western blotting and RT-PCR, than the controls. The expression of the transcription coactivator PGC-1alpha in both tissues was also significantly elevated in the BM-supplemented rats (P < 0.05). The present results suggest that decreased adiposity in BM-supplemented rats may result from lower metabolic efficiency, a consequence of increased lipid oxidation and mitochondrial uncoupling.

The High-Fat Diet–Fed Mouse

This study characterizes the high-fat diet-fed mouse as a model for impaired glucose tolerance (IGT) and type 2 diabetes. Female C57BL/6J mice were fed a high-fat diet (58% energy by fat) or a normal diet (11% fat). Body weight was higher in mice fed the high-fat diet already after the first week, due to higher dietary intake in combination with lower metabolic efficiency. Circulating glucose increased after 1 week on high-fat diet and remained elevated at a level of approximately 1 mmol/l throughout the 12-month study period. In contrast, circulating insulin increased progressively by time. Intravenous glucose challenge revealed a severely compromised insulin response in association with marked glucose intolerance already after 1 week. To illustrate the usefulness of this model for the development of new treatment, mice were fed an orally active inhibitor of dipeptidyl peptidase-IV (LAF237) in the drinking water (0.3 mg/ml) for 4 weeks. This normalized glucose tolerance, as judged by an oral glucose tolerance test, in association with augmented insulin secretion. We conclude that the high-fat diet-fed C57BL/6J mouse model is a robust model for IGT and early type 2 diabetes, which may be used for studies on pathophysiology and development of new treatment.

Paleoecological reconstruction of a lower Pleistocene large mammal community using biogeochemical (δ13C, δ15N, δ18O, Sr:Zn) and ecomorphological approaches

Ecomorphological and biogeochemical (trace element, and carbon, nitrogen, and oxygen isotope ratios) analyses have been used for determining the dietary niches and habitat preferences of large mammals from lower Pleistocene deposits at Venta Micena (Guadix-Baza Basin, Spain). The combination of these two approaches takes advantage of the strengths and overcome the weakness of both approaches. The range of δ13Ccollagen values for ungulate species indicates that C3 plants were dominant in the diet of these mammals. δ13Ccollagen values vary among ungulates: perissodactyls have the lowest values and bovids the highest ones, with cervids showing intermediate values. The hypsodonty index measured in lower molar teeth and the relative length of the lower premolar tooth row indicate that the horse, Equus altidens, was a grazing species, whereas the rhino, Stephanorhinus etruscus, was a mixed feeder in open habitats. The similar δ13Ccollagen values shown in both perissodactyls does not reflect differences in feeding behavior with other ungulates, but rather a lower isotope enrichment factor in these monogastric herbivores than in ruminants, owing to their lower metabolic efficiency. The cervids Eucladoceros giulii and Dama sp. show low hypsodonty values, indicating that they were mixed feeders or browsers from forested habitats, an ecomorphologically based conclusion corroborated in the former by its low δ15Ncollagen content (canopy effect). Bovid species (Bovini aff. Leptobos, Soergelia minor, and Hemitragus albus) presumably inhabited open environments, according to their comparatively high hypsodonty and δ15Ncollagen values. Carnivore species (Homotherium latidens, Megantereon whitei, Pachycrocuta brevirostris, Canis falconeri, and Canis etruscus) exhibit higher δ15Ncollagen values than ungulates. These results record the isotopic enrichment expected with an increase in trophic level and are also supported by low bone Sr.Zn ratios. The elevated δ15Ncollagen value for a sample of Mammuthus meridionalis, which came from an individual with unfused epiphyses, confirms that it was a suckling animal. The δ15Ncollagen value of the scimitar-cat H. latidens is well above that obtained for the young individual of Mammuthus, which indicates that juvenile elephants were an important part of its diet. The hippo, Hippopotamus antiquus, yielded unexpectedly high δ15Ncollagen values, which suggest feeding on aquatic, non-N2-fixing plants. The high δ18Ohydroxyl values of bovids Hemitragus and Soergelia and of cervid Dama indicate that these ungulates obtained most of their water requirements from the vegetation. The megaherbivores and Eucladoceros exhibit the lowest δ18Ohydroxyl values, which suggest increased water dependence for them. Paleosynecological analysis was based on the relative abundance of species of large mammals from different ecological categories, determined by feeding behavior and locomotion types. The comparison of the frequencies of such categories in Venta Micena with those found in modern African communities indicates that the composition of the paleocommunity closely resembles those of savannas with tall grass and shrubs. The net above-ground primary productivity estimated for the on-crop biomass of the mammalian species preserved in the fossil assemblage also yields a figure congruent with that expected for an open environment.

Fluctuating asymmetry and psychometric intelligence.

Little is known about the genetic nature of human psychometric intelligence (IQ), but it is widely assumed that IQ's heritability is at loci for intelligence per se. We present evidence consistent with a hypothesis that interindividual IQ differences are partly due to heritable vulnerabilities to environmental sources of developmental stress, an indirect genetic mechanism for the heritability of IQ. Using fluctuating asymmetry (FA) of the body (the asymmetry resulting from errors in the development of normally symmetrical bilateral traits under stressful conditions), we estimated the relative developmental instability of 112 undergraduates and administered to them Cattell's culture fair intelligence test (CFIT). A subsequent replication on 128 students was performed. In both samples, FA correlated negatively and significantly with CFIT scores. We propose two non-mutually exclusive physiological explanations for this correlation. First, external body FA may correlate negatively with the developmental integrity of the brain. Second, individual energy budget allocations and/or low metabolic efficiency in high-FA individuals may lower IQ scores. We review the data on IQ in light of our findings and conclude that improving developmental quality may increase average IQ in future generations.

Environmental Changes and Evolution of Marine Invertebrates from the Late Precambrian to the Cambrian

The rapid appearance of skeletons in various marine invertebrates in the beginning of the Cambrian produced the sudden explosive increase of the animal fossils. This dramatic evolutionary event was not performed by the explosive diversification of marine life but simply by the physiological changes of the organisms in increasing oxygen pressure in the earth's atmosphere. According to the recent physiological studies, various marine animals can survive in low dissolved oxygen conditions of rather long period with an anaerobic metabolism, suggesting the respiratory mechanisms of the primitive forms in the Precambrian. The anaerobic metabolic activities imposed some physiological restrictions on the animals through the acidic end-products (eg, inhibition of skeleton formation, small body size, and low metabolic efficiency etc.). The skeleton formation in the Cambrian life was initiated by the advent of aerobic metabolism, which indicated the release from the physiological restrictions by the anaerobic metabolism.

Assimilation Efficiency of Sanderlings (Calidris alba) Feeding on Horseshoe Crab (Limulus polyphemus) Eggs

Sanderlings (Calidris alba) feed extensively on horseshoe crab (Limulus polyphemus) eggs during their 4-wk spring migratory stopover on beaches in Delaware Bay. To assess metabolizable energy (ME) present in such a diet, we studied the assimilation efficiency of seven captive C. alba fed a Limulus egg diet for 3 wk. Each bird ingested on average 30.9 g eggs d⁻¹ (or approximately 8,300 eggs d⁻¹). The average metabolic efficiency was 38.6% ± 1.0%. Associated with this low metabolic efficiency was a rapid gastrointestinal passage rate of 63 ± 2.5 min (n = 4). While on the Limulus egg diet, the birds maintained body weight (51.3 ± 5.2 g); when switched to a diet of mealworms (Tenebrio larvae), they rapidly gained weight (1.8 ± 0.20 g d⁻¹) and exhibited an average metabolic efficiency of 75.9% ± 8.0%. We attributed the poor assimilation efficiency exhibited by C. alba when feeding on Limulus eggs to the resistance of the egg cuticle to chemical and enzymatic digestion; 72% of the ingested eggs are passed throu...

The effect of temperature on feeding, growth, and metabolism during the last larval stadium of the female house cricket, Acheta domesticus

Eighth instar female house crickets at 35°C developed faster, gained slightly more wet weight, and consumed less food, water, and oxygen than at 25°C. The duration of the 8th stadium at 25°C was 13 days (undisturbed), but was 14 days when disturbed by daily weighing. The duration of the 8th stadium at 30°C was 8 days and at 35°C was 6 days. During the first half of the 8th stadium at 25, 30, and 35°C, there was a high rate of food and water consumption resulting in statistically equal maximum dry weight achievement (124 mg). Respiratory quotients greater than one during this time indicated the conversion of ingested carbohydrate to fat. During the latter half of the 8th stadium, food and water consumption declined and the crickets lost weight. The period of weight loss was proportionally much longer at 25°C than at 30 or 35°C. Respiratory quotients lower than 1.0 during the latter half of the 8th stadium at 30 and 35°C indicated the metabolism of stored lipids. The respiratory quotient at 25°C never fell below 1.0, possibly because some food remained in the gut. The absorption efficiency was not influenced by temperature (25–35°C). Though the caloric content of the faeces was lower at 25°C than at 30 or 35°C, which correlated to the much longer time for food passage at 25°C than at 35°C, the difference in total calories egested was insufficient to alter the absorption efficiency. A longer period of reduced feeding and greater dry weight loss during the latter half of the 8th stadium at 25°C resulted in a lower metabolic efficiency at 25°C than at 30 or 35°C. Eighth instar crickets in response to a step-function transfer from 30°C–25 or 35°C showed an immediate (<1 hr) and complete metabolic adjustment which was not affected by the temperature history during the 7th stadium. House crickets did not exhibit temperature acclimation in the range 20–40°C, the metabolic rate being determined by ambient temperature. The Q 10 for oxygen consumption in the range 20–40°C was about 2.