Sudden Environmental Changes Research Articles

Transcriptional response to heat shock in liver of snow trout (Schizothorax richardsonii)--a vulnerable Himalayan Cyprinid fish.

The snow trout (Schizothorax richardsonii) belonging to family Cyprinidae, is an endemic fish of the Himalayan region. The species is tagged as vulnerable species in the IUCN red list of threatened species. The fish thrives well in snowmelt water of several streams and rivers in the region but are occasionally exposed to more than 20 °C during the summer season. Therefore, we have used deep RNA sequencing to decipher the transcriptome of snow trout and characterize the genes and molecular pathways involved in heat shock response. In this study 72,601,298 and 65,428,283 raw reads for heat-shocked and control, respectively, were obtained by Illumina paired-end sequencing technology. The de novo assembled transcriptome was tested for differential gene expression across the treatment groups. The quality of assembly was high with N75 and N50 lengths of 461 and 1274 bases, respectively. A total of 65 unique transcripts were differentially expressed in liver under heat shock and control. Annotated blast matches reveal that differentially expressed transcripts correspond to critical chaperones and molecular pathways, previously shown to be important for thermal stress in other fish species. Eight randomly selected heat-stressed responsive transcripts were also observed to be upregulated during qRT-PCR analysis. This study is the preliminary step to understanding the responses during sudden environmental changes like heat shock. The reference transcriptome database would also aid further studies on biological and physiological aspects of the snow trout under abiotic stresses.

Morphology-based functional groups as effective indicators of phytoplankton dynamics in a tropical cyanobacteria-dominated transitional river–reservoir system

Cyanobacteria dominance is often associated with economic, ecological and health problems. The potential production of toxic compounds calls for frequent monitoring of cyanobacteria and their toxin production in many aquatic systems. Methods to simplify this process and facilitate management responses to sudden environmental changes are needed to improve the capability of risk-assessment. We tested the effectiveness of two different functional approaches (Functional Groups – FG, Reynolds et al., 2002; and Morphology-Based Functional Groups – MBFG, Kruk et al., 2010) as well as single species and taxonomic classifications as the best proxy of spatio-temporal phytoplankton dynamics and dominance of toxic algae in an impacted transitional river–reservoir system in the tropics. The Paraíba do Sul River and Funil Reservoir are located in one of the most heavily impacted regions of Brazil, and the latter system has a history of intense, long-lasting toxic cyanobacteria blooms. Sampling was conducted over the two climatological periods of the region: warm-rainy (October/2011 and January/2012) and cold-dry (July/2011 and May/2012), with stations in the following areas: tributary, reservoir and river (downstream from the dam). Our results showed that the MBFG classification was the most effective approach, i.e., best explained the response of the phytoplankton community to environmental variations. Environmental factors including light, nutrients, water temperature and hydrology increased the occurrence of different MBFGs on both spatial and temporal scales. The lotic areas showed a more diverse composition of MBFGs, including species with high to moderate tolerance to light limitation and flushing conditions (MBFGs I, III, IV, V and VI). In Funil Reservoir, phytoplankton biovolume was dominated by bloom-forming cyanobacteria (MBFGs III and VII) and remained high throughout the study. This dominance was related to the overall eutrophic conditions, low light availability and increased water-column stability of the reservoir. The seasonal dynamics in the reservoir was mainly related to changes in temperature and hydrology. Our results show for the first time that morphology captures efficiently eco-strategies of bloom-forming cyanobacteria and the MBFG approach can be used to predict and monitor the development of cyanobacteria HABs in temporal and spatial scales.

Non-invasive measurement of adrenocortical activity in a myrmecophageous mammal, the bat-eared fox

Measuring physiological stress reactions through the quantification of plasma cortisol often involves physical restraint, which acts as a stressor itself. Here, we present the validation of a non-invasive method for assessing adrenocortical activity as an indicator of stress in the bat-eared fox (Otocyon megalotis). By conducting an adrenocorticotropic hormone (ACTH) challenge, we examined the suitability of three enzyme immunoassays (EIAs) detecting 11,17 dioxoandrostanes (11,17-DOA) as well as faecal glucocorticoid metabolites (fGCM) with a 5β-3α-ol-11-one (3α,11oxo-CM), or 11,17,21-trihydroxy-4-ene-20-one structure (cortisol), respectively, for monitoring stress-related physiological responses in male and female bat-eared foxes. Our results suggest that the cortisol EIA seems most suitable for measuring fGCMs in this myrmecophageous mammal. Using the cortisol EIA, we compared fGCM concentrations of three populations of foxes. Only one population experienced a sudden change in social environment and the assay appeared to effectively detect the expected resulting increase in stress hormone levels. Therefore, the identified EIA is effective at detecting intraspecific variation in fGCM levels and hence is a useful tool to evaluate physiological stress responses in this species.

Robust filtering for Markovian jump neutral systems with distributed delays

ABSTRACTOver the past decades, a great deal of attention has been devoted to parameter-invariant neutral systems. However, in practical applications, the jump of parameters frequently occurs to neutral systems on account of sudden environmental changes, which can be described by Markovian jump systems. This paper mainly deals with the problem of robust filtering for uncertain Markovian jump neutral systems with distributed delays. The uncertain parameters are assumed to be time varying and norm bounded. By utilizing the Newton–Leibniz formula and integral inequality technique, the delay-dependent sufficient conditions for the existence of the filter are derived such that the filtering error system is stochastically stable with an performance constraint. Based on the obtained criteria and by employing congruent transformation, the robust filter is designed in terms of linear matrix inequalities. Finally, a numerical example is provided to illustrate the effectiveness of the proposed method.

The Role of Recombination in Evolutionary Rescue.

How likely is it that a population escapes extinction through adaptive evolution? The answer to this question is of great relevance in conservation biology, where we aim at species' rescue and the maintenance of biodiversity, and in agriculture and medicine, where we seek to hamper the emergence of pesticide or drug resistance. By reshuffling the genome, recombination has two antagonistic effects on the probability of evolutionary rescue: it generates and it breaks up favorable gene combinations. Which of the two effects prevails depends on the fitness effects of mutations and on the impact of stochasticity on the allele frequencies. In this article, we analyze a mathematical model for rescue after a sudden environmental change when adaptation is contingent on mutations at two loci. The analysis reveals a complex nonlinear dependence of population survival on recombination. We moreover find that, counterintuitively, a fast eradication of the wild type can promote rescue in the presence of recombination. The model also shows that two-step rescue is not unlikely to happen and can even be more likely than single-step rescue (where adaptation relies on a single mutation), depending on the circumstances.

Response of green hydra (Hydra viridissima) to variability and directional changes in food availability

AbstractNatural environments tend to be variable resulting in alternating periods of high and low food availability. Therefore, animals have to be able to accommodate to sudden environmental changes by adjusting their physiology and behaviour to new conditions. We investigated how simulated food variability affects life history traits (asexual reproduction and stress tolerance) and response to environmental change in laboratory experiments with green hydra (Hydra viridissima). We assigned hydra into four groups differing in feeding frequency (high or low) and food regularity (random or stable). After 21 days of accommodation, feeding frequency was changed (increased or decreased) in half of each group, the other half was kept as a control group. Hydra showed a delayed response to environmental change (increased or decreased feeding frequency). This delay in response was greater under an unpredictable feeding scheme. Animals on a random scheme had lower budding rates and lower stress tolerance. Follow-up experiments suggest that this might be due to receiving food on subsequent days, since we found that animals fed daily have lower budding rates than those fed on alternate days. We hypothesize that frequent feeding might cause high levels of oxidative/xenobiotic stress which could overwhelm the defence system of these animals.

The response of small and medium-sized enterprises to potential water risks: an eco-cluster approach

This paper investigates the perception of mangers of small and medium-sized enterprises (SMEs) in undertaking collaborative forms to overcome the weaknesses faced by individual SMEs in an attempt to tackle production and operational risks associated with water issues. It particularly examines the effect of water related problems on the operations of SMEs mainly as a result of excessive and sudden environmental changes (e.g. droughts and floods) and strict public policy requirements (e.g. the Clean Water Act). Current literature examines these reasons at an individual firm level and mainly for large firms. To fill this gap, this paper focuses on examining these issues in SMEs. A case study was conducted on a sample of 10 SMEs located in Northern Greece and operating in the food industry in order to examine the perceptions of managers/owners of SMEs regarding the suitability of collaborative forms to face potential water risks. The findings showed that despite the low awareness of managers/owners of SMEs concerning the effects of water risks on their operations, they considered collaboration between SMEs as a good tool for eliminating water risks and gaining financial benefits.

Regulatory principles governing Salmonella and Yersinia virulence.

Enteric pathogens such as Salmonella and Yersinia evolved numerous strategies to survive and proliferate in different environmental reservoirs and mammalian hosts. Deciphering common and pathogen-specific principles for how these bacteria adjust and coordinate spatiotemporal expression of virulence determinants, stress adaptation, and metabolic functions is fundamental to understand microbial pathogenesis. In order to manage sudden environmental changes, attacks by the host immune systems and microbial competition, the pathogens employ a plethora of transcriptional and post-transcriptional control elements, including transcription factors, sensory and regulatory RNAs, RNAses, and proteases, to fine-tune and control complex gene regulatory networks. Many of the contributing global regulators and the molecular mechanisms of regulation are frequently conserved between Yersinia and Salmonella. However, the interplay, arrangement, and composition of the control elements vary between these closely related enteric pathogens, which generate phenotypic differences leading to distinct pathogenic properties. In this overview we present common and different regulatory networks used by Salmonella and Yersinia to coordinate the expression of crucial motility, cell adhesion and invasion determinants, immune defense strategies, and metabolic adaptation processes. We highlight evolutionary changes of the gene regulatory circuits that result in different properties of the regulatory elements and how this influences the overall outcome of the infection process.

The sedimentary record of the 1960 tsunami in two coastal lakes on Isla de Chiloé, south central Chile

This study describes sediments deposited by the tsunami following the 1960 Great Chilean Earthquake (MW 9.5) in two coastal lakes, Lakes Cucao and Huelde, on the west coast of Isla de Chiloé, south central Chile (42.6°S). Sub-bottom profiles and side scan sonar mosaics illustrate the sedimentary context of transects of gravity cores. The stratigraphy of both lakes features gyttja sedimentation, interrupted by the abrupt emplacement of a sandy layer with mud rip-up clasts and a mud cap. This sandy layer reflects a sudden change in sedimentary environment, most probably caused by a high-energy inundation. Radionuclide analyses (137Cs and 210Pb) date the inundation deposit to shortly before the mid 1960s. The only known event that matches the sedimentological and chronological criteria is the AD 1960 tsunami. Using grain size analysis and comparisons with samples from modern environments, we demonstrate that the proximal (seaward) part of the deposit consists of a mixture of sand derived from subaerial sources and reworked gyttja lake sediment. In the distal (landward) part of Lake Cucao, the sand component is lost and the deposit consists entirely of remobilised lake sediments. The repetition of tsunami deposit sequences in Lake Huelde suggests a minimum of three inundating waves. Sub-bottom profiles and side scan sonar mosaics reveal tsunami inundation over the barrier and more prominently through the outlet river channel. The dominant role of the river channel as a pathway for sediment transport is also described in core samples by tsunami deposits that fine away from the channel mouth. The identification and description of the deposit left by a known tsunami provide important insights into tsunami sedimentation in coastal lakes and have the potential to help in the search for paleotsunami evidence.

E. coli DH5α cell response to a sudden change in microfluidic chemical environment.

Motile bacteria respond to changing chemical environment by moving towards or away from a particular location. Bacterial migration under chemical gradient is one of the most studied areas in biomedical field. In this work we looked into how bacterial cells respond to sudden change in the microfluidic chemical environment. E. coli DH5α cells were subjected to an attractant gradient (0.1 mM sorbitol--attractant to E. coli cells) and after 120 min the same cells were exposed to an inhibitor (0.1 mM NiSO4) gradient in the same microfluidic device. Our studies revealed that when the E. coli DH5α cells were exposed to 0.1 mM sorbitol, they showed faster chemotaxis towards the attractant (0.1 mM sorbitol) and achieved steady state by 60 min. When we replaced 0.1 mM sorbitol with 0.1 mM NiSO4 in the device we found that that the E. coli DH5α cells started responding to change in chemical environment within 10 min and achieved steady state at the end of 60 min. This shows that the bacterial cells respond to change in local chemical environment is within few minutes.

Transfer RNAs Mediate the Rapid Adaptation of Escherichia coli to Oxidative Stress.

Translational systems can respond promptly to sudden environmental changes to provide rapid adaptations to environmental stress. Unlike the well-studied translational responses to oxidative stress in eukaryotic systems, little is known regarding how prokaryotes respond rapidly to oxidative stress in terms of translation. In this study, we measured protein synthesis from the entire Escherichia coli proteome and found that protein synthesis was severely slowed down under oxidative stress. With unchanged translation initiation, this slowdown was caused by decreased translation elongation speed. We further confirmed by tRNA sequencing and qRT-PCR that this deceleration was caused by a global, enzymatic downregulation of almost all tRNA species shortly after exposure to oxidative agents. Elevation in tRNA levels accelerated translation and protected E. coli against oxidative stress caused by hydrogen peroxide and the antibiotic ciprofloxacin. Our results showed that the global regulation of tRNAs mediates the rapid adjustment of the E. coli translation system for prompt adaptation to oxidative stress.

Warning signals for eruptive events in spreading fires

Spreading fires are noisy (and potentially chaotic) systems in which transitions in dynamics are notoriously difficult to predict. As flames move through spatially heterogeneous environments, sudden shifts in temperature, wind, or topography can generate combustion instabilities, or trigger self-stabilizing feedback loops, that dramatically amplify the intensities and rates with which fires propagate. Such transitions are rarely captured by predictive models of fire behavior and, thus, complicate efforts in fire suppression. This paper describes a simple, remarkably instructive physical model for examining the eruption of small flames into intense, rapidly moving flames stabilized by feedback between wind and fire (i.e., "wind-fire coupling"-a mechanism of feedback particularly relevant to forest fires), and it presents evidence that characteristic patterns in the dynamics of spreading flames indicate when such transitions are likely to occur. In this model system, flames propagate along strips of nitrocellulose with one of two possible modes of propagation: a slow, structured mode, and a fast, unstructured mode sustained by wind-fire coupling. Experimental examination of patterns in dynamics that emerge near bifurcation points suggests that symptoms of critical slowing down (i.e., the slowed recovery of the system from perturbations as it approaches tipping points) warn of impending transitions to the unstructured mode. Findings suggest that slowing responses of spreading flames to sudden changes in environment (e.g., wind, terrain, temperature) may anticipate the onset of intense, feedback-stabilized modes of propagation (e.g., "blowup fires" in forests).

An Exponential Melanoma Trend Model

The present study investigated whether whole population exposure to radiation introduced by radio broadcasting and cell phone systems might explain recent increases in melanoma trends in Nordic countries or not. Trends were modeled using a single exponential function of the time each age group has been living in the new environment since an environmental change took place. The results clearly show that melanoma incidences started to increase exponentially by the time lived as an adult since 1955 and that a second trend break occurred in 1997. We searched best fit between calculated and reported age-standardized rates by parameter variation, and compared calculated with reported age-specific rates without further parameter adjustments. Local variations of breast cancer, lung cancer and all cancers together significantly correlated with corresponding local melanoma rates in Sweden. Increasing cancer trends since around 1997 seem related to a population covering environmental change effective from early 90’s. We conclude that this exponential trend model can be a useful tool in understanding responses to sudden environmental changes.

Solar-induced Thermal Activity and Stratification in Pond Water

Ponds are universally used to store water for a large number of uses. With the increasing demand for more fresh water, ponds, lakes and reservoirs are likely to be constructed on a larger scale. We must understand the effects of environmental changes on fresh water if we are to most efficiently utilize this resource. This study undertakes to increase our understanding of the rate of thermal response of ponds and other bodies of water to every-day environmental changes. The central research agenda is to investigate how the temperature of pond water from top to bottom responds to the day/night cycle, changes in air temperature just above the surface, cloud conditions, and other sudden environmental changes. Data collection for this study spanned October 2007 to June 2011 and had a continuous time resolution of 50 seconds.

Plant pathogen evolution and climate change.

Abstract The earth's system is currently experiencing dramatic climate change, with predicted rates of global-mean temperature increase unprecedented in the past 1000 years. Also temperature patterns at the local scale and precipitation regimes are rapidly changing. Extreme climatic events are becoming more intense and frequent, especially on the regional scale. Such sudden environmental changes reduce the time for adaptation and increase the vulnerability of natural ecosystems. Plant pathogens have three major adaptive responses to climate change: to exploit the existing phenotypic plasticity, to migrate to areas with more suitable climate and/or to evolve new attributes. Plastic genotypes may quickly adapt to a broad range of environmental conditions, but if phenotypic plasticity is insufficient, migration and/or evolution (which are facilitated by large population size, mixed mating system and parasexuality) are the only options. Global trade in live plants, which is nowadays the main pathway of introduction of alien plant pathogens to new areas, further complicates the picture. Once introduced into a new environment, pathogens may adapt their lifestyle to new local hosts (host jump), or evolve by introgressing useful genes for adaptation through hybridization with resident species or horizontal gene transfer. The implications of climate change for plant pathogens are difficult to predict, but since pathogens have an array of adaptive mechanisms much wider than their hosts and shorter generation times, their opportunities to adapt/evolve will probably increase. New strategies for predicting and monitoring plant pathogen evolution need to be developed to prevent the spread of new plant pathogens on naive or vulnerable hosts likely weakened by climate change pressure.

Stress Testing of Retail and Corporate Segments of Russian Credit Market

The objective of the paper is to investigate and compare risk patterns in retail and corporate segments and assess the potential impact of macroeconomic shocks on loan quality. Banks’ monthly financial statements data for the period 2004 – 2012 are used. Firstly, we develop an indicator to measure institution’s credit risk that reflects variance and average value of NPL corrected for loan loss reserves. It is used to compare the risk-return patterns of largest state-owned banks, and under our framework we identify how the strategies of various banks differ in retail and corporate loans, identifying ‘safest’ and ‘riskiest’ institutions. Secondly, loan growth and credit risk sensitivity to macroeconomic shocks is analyzed using vector auto-regression. Macroeconomic shocks do not significantly increase NPL growth in the corporate segment. However, inflation and investment growth have a considerable impact on NPL growth in the retail segment (which is however almost three times less than the corporate). Based on these findings we conclude that there is no reason to expect rampant rise in corporate loan defaults in response to sudden changes in macroeconomic environment of Russia, though further growth of corporate loan segment increases credit risk, while the opposite is true about the retail sector.

PGC-1α mediates a rapid, exercise-induced downregulation of glycogenolysis in rat skeletal muscle.

Long-term endurance exercise training results in a reduction in the rates of muscle glycogen depletion and lactic acid accumulation during submaximal exercise; this adaptation is mediated by an increase in muscle mitochondria. There is evidence suggesting that short-term training induces adaptations that downregulate glycogenolysis before there is an increase in functional mitochondria. We discovered that a single long bout of exercise induces decreases in expression of glycogenolytic and glycolytic enzymes in rat skeletal muscle; this adaptation results in slower rates of glycogenolysis and lactic acid accumulation in muscle during contractile activity. Two additional days of training amplified the adaptive response, which appears to be mediated by PGC-1α; this adaptation is biologically significant, because glycogen depletion and lactic acid accumulation are major causes of muscle fatigue. Endurance exercise training can increase the ability to perform prolonged strenuous exercise. The major adaptation responsible for this increase in endurance is an increase in muscle mitochondria. This adaptation occurs too slowly to provide a survival advantage when there is a sudden change in environment that necessitates prolonged exercise. In the present study, we discovered another, more rapid adaptation, a downregulation of expression of the glycogenolytic and glycolytic enzymes in muscle that mediates a slowing of muscle glycogen depletion and lactic acid accumulation. This adaptation, which appears to be mediated by PGC-1α, occurs in response to a single exercise bout and is further enhanced by two additional daily exercise bouts. It is biologically significant, because glycogen depletion and lactic acid accumulation are two of the major causes of muscle fatigue and exhaustion.

Effects of impoundment on the body condition of fish in the Manso reservoir, Mato Grosso State, Brazil

AIM: This study evaluated the body condition de Acestrorhynchus pantaneiro, Auchenipterus osteomystax, Pimelodus maculatus, Psectrogaster curviventris and Schizodon borellii in the Manso reservoir, Mato Grosso State, Brazil, during the first years after its formation (years I, II, III and IV). We hypothesized that sudden environmental changes alter differently the body condition, according to the time (sampling years) and sex of individuals. Also, we checked the influence of the amount of food ingested and the reproductive status on nutritional status of the species. METHODS: The body condition (Kn), the feeding activity (SRI) and reproductive (GSI) were calculated only for adults. The difference between the sampling years and sexes (used as factors) was assessed using the nonparametric Kruskal-Wallis test. Temporal influence was tested by Spearman correlation and the interaction between both factors by PERMANOVA. RESULTS: The values of the Kn showed two groups: group 1: species whose body condition decreased in the year II, with a posterior increase (A. pantaneiro, P. curviventris and S. borelli), considered sensitive to the reservoir filling; group 2: species whose body condition increased in the year II (A. osteomystax and P. maculatus), indicating a more rapid adaptation to new environmental conditions. Still, all parameters investigated were somehow affected by the dam, mainly the body condition and gonadosomatic index for several species. On the other hand, the least affected factor was the feeding activity. CONCLUSIONS: The results did not evidence a same pattern of either increase or decrease of body condition for all species examined, since everything indicates that responses are species-specific. Even with a lack of consistency in some results, we can draw some suggestions for future investigations. Responses to these questions will certainly contribute to aggregate data to help better explain the body condition of fish species in dammed environments.

Path Planning Problem

Path planning is the way of determination of a collision free path between start and goal position through obstacles cluttered in a workspace. Though it is a complex problem, but it is an essential task for the navigation and controlling the motion of autonomous robot manipulators. This NP-complete problem (those problems is difficult to solve specially in a dynamic environment where the optimal path needs to be rerouted in real time when a new obstacle appears. This paper provides two categories of path planning approaches:Deterministic and Probabilistic approaches. Deterministic methods allow achieving the same result in each execution with the same initial conditions. They are perfectly predictable, hence suitable for static environment, but not effective when they are used in a real time environment as there could be sudden changes in environment. The most used solution to overcome the problem of real time environment are the probabilistic methods such as Particle swarm optimization[pso], Ant colony optimization[aco], genetic algorithm[ga], multi agent path planning,etc. General Terms Deterministic algorithm, probabilistic algorithm, aco, pso, ga, A*algorithm, dijkstra, multi agent path planning.

The population genetics of evolutionary rescue.

Evolutionary rescue occurs when a population that is threatened with extinction by an environmental change adapts to the change sufficiently rapidly to survive. Here we extend the mathematical theory of evolutionary rescue. In particular, we model evolutionary rescue to a sudden environmental change when adaptation involves evolution at a single locus. We consider adaptation using either new mutations or alleles from the standing genetic variation that begin rare. We obtain several results: i) the total probability of evolutionary rescue from either new mutation or standing variation; ii) the conditions under which rescue is more likely to involve a new mutation versus an allele from the standing genetic variation; iii) a mathematical description of the U-shaped curve of total population size through time, conditional on rescue; and iv) the time until the average population size begins to rebound as well as the minimal expected population size experienced by a rescued population. Our analysis requires taking into account a subtle population-genetic effect (familiar from the theory of genetic hitchhiking) that involves “oversampling” of those lucky alleles that ultimately sweep to high frequency. Our results are relevant to conservation biology, experimental microbial evolution, and medicine (e.g., the dynamics of antibiotic resistance).