Environmental Variables Temperature Research Articles

Field Relevant Variation in Ambient Temperature Modifies Density-Dependent Establishment of Plasmodium falciparum Gametocytes in Mosquitoes.

The relationship between Plasmodium falciparum gametocyte density and infections in mosquitoes is central to understanding the rates of transmission with important implications for control. Here, we determined whether field relevant variation in environmental temperature could also modulate this relationship. Anopheles stephensi were challenged with three densities of P. falciparum gametocytes spanning a ~10-fold gradient, and housed under diurnal/daily temperature range (“DTR”) of 9°C (+5°C and −4°C) around means of 20, 24, and 28°C. Vector competence was quantified as the proportion of mosquitoes infected with oocysts in the midguts (oocyst rates) or infectious with sporozoites in the salivary glands (sporozoite rates) at peak periods of infection for each temperature to account for the differences in development rates. In addition, oocyst intensities were also recorded from infected midguts and the overall study replicated across three separate parasite cultures and mosquito cohorts. While vector competence was similar at 20 DTR 9°C and 24 DTR 9°C, oocyst and sporozoite rates were also comparable, with evidence, surprisingly, for higher vector competence in mosquitoes challenged with intermediate gametocyte densities. For the same gametocyte densities however, severe reductions in the sporozoite rates was accompanied by a significant decline in overall vector competence at 28 DTR 9°C, with gametocyte density per se showing a positive and linear effect at this temperature. Unlike vector competence, oocyst intensities decreased with increasing temperatures with a predominantly positive and linear association with gametocyte density, especially at 28 DTR 9°C. Oocyst intensities across individual infected midguts suggested temperature-specific differences in mosquito susceptibility/resistance: at 20 DTR 9°C and 24 DTR 9°C, dispersion (aggregation) increased in a density-dependent manner but not at 28 DTR 9°C where the distributions were consistently random. Limitations notwithstanding, our results suggest that variation in temperature could modify seasonal dynamics of infectious reservoirs with implications for the design and deployment of transmission-blocking vaccines/drugs.

Effects of subjective feeling of environmental temperature on appetite and food intake in Chinese sociodemographic and ethnic groups

BackgroundA better understanding of the effect of environmental temperature variation on appetite and food intake may inform the public of adopting appropriate prophylactic eating behaviors. Seasonal weather temperature variation has been shown to have adverse effects on appetite and food intake in humans. The main purpose of this study was to examine the effect of environmental temperature variation on the appetite and eating patterns in Chinese adults.MethodsCross-sectional analysis of data obtained from 1297 Chinese adults, including two Chinese ethnic groups, Han (N = 897) and Hui (N = 400). Participants responded to a modified paper-and-pencil self-administered dietary habits and food intake survey. In addition to sociodemographic factors and ethnic group affiliation questions, the survey included a question regarding the effect of the subjective feeling of environmental temperature variation (SFETV) on appetite and food intake as an independent variable.t tests and chi-square analyses were performed to analyze the parametric and nonparametric variables respectively.ResultsNo significant difference was found in the effect of SFETV between the following dependent variables: male and female respondents (p < .998), married and single respondents (p < .281), full-time and part-time employed or retired participants (p < .187). Although it has not affected their SFETV responses, there was a statistically significant difference in the education level between the married and single respondents (p < .001). The single respondents were more likely to be college educated with a rate of (68.48%) compared with their married counterparts with a rate of 30.2%. There was a statistically significant difference between the eight cities and one rural town (p < .001). The appetite and food intake of the respondents from these cities were more likely to be affected by the SFETV. The appetite and food intake of the Han ethnic group were more likely to be affected by the SFETV with a rate of 28.09% juxtaposed to the Hui ethnic group with a rate of 12.64%.ConclusionsThe findings suggest that exposure to outdoor temperature variation (hot or cold) has a limited effect on the appetite and food intake of Chinese adults. However, the appetite and food intake of the permanent residents of the eight cities and one rural town were more likely to be affected by the exposure to outdoor temperature variation (hot or cold).

Simulation of optical properties of thermochromic film: Influences of particle configuration and geometry

Thermochromic (TC) materials are one of smart materials which could reversibly change colors/optical properties in response to the variation in environmental temperature. TC film with embedded TC pigment, facilitates temperature management of infrastructures to improve energy efficiency of buildings and durability of pavement. However, the effectiveness of TC film is dictated by its optical properties. This study aims to optimizing temperature-dependent optical behaviors of TC film in terms of particle configuration and geometry of TC pigment by conducting finite element simulation and applying Kubelka-Munk model. The analysis shows that TC film with bi-sphere particles achieves total diffuse reflectance of 10% for dark-colored TC pigment and 11% for light-colored TC pigment, which is negligibly affected by particle configuration. When changing particle shape from sphere to rod, the total diffuse reflectance of TC film is enhanced to 16% below the transition temperature and 18% above the transition temperature. Moreover, as the length to diameter ratio of nanorod increases, the total diffuse reflectance of TC film decreases. The computational framework provides guideline to optimize the design of TC film with desirable optical properties of TC film.

Proposal of a Feedback Control System for a Thermally Driven High-Power-Density Actuator

Shape memory alloy (SMA) actuators can generate force via the phase transition of the SMA, related to its temperature variations. The amount of force and the response duration length are approximately proportional to the SMA’s volume and mass. The higher-power actuator, which consists of a single SMA tube, has mechanical simplicity and high reliability; however, it has a relatively long driving duration, and actuation timing uncertainties caused by the environmental temperature variations. Because of its huge heat capacity, the environment temperature variations affect the actuator’s temperature, the phase transformation uncertainties, and force generation profiles, resulting in differences in the actuation timing that are tens of seconds. This paper proposes a suitable feedback control system consisting of two methods. One is the construction of a physical model for SMA tube thermomechanical coupling response that has suitable complexity for the real-time control system design by the limited application condition. The other is a reference trajectory generation and tracking method by using the model predictive control method with a constructed physical model, resulting in a possible drive timing uncertainty reduction. The effectiveness of the proposed methods was verified by specific test piece system identification and control simulations performed both numerically and experimentally. In addition, the effectiveness of the online control system itself was confirmed by comparing the results of a traditional control system using the proportional integral derivative method. The result indicates the potential of the possible application system for SMA actuators.

Competition and succession among coral endosymbionts.

Host species often support a genetically diverse guild of symbionts, the identity and performance of which can determine holobiont fitness under particular environmental conditions. These symbiont communities are structured by a complex set of potential interactions, both positive and negative, between the host and symbionts and among symbionts. In reef‐building corals, stable associations with specific symbiont species are common, and we hypothesize that this is partly due to ecological mechanisms, such as succession and competition, which drive patterns of symbiont winnowing in the initial colonization of new generations of coral recruits. We tested this hypothesis using the experimental framework of the de Wit replacement series and found that competitive interactions occurred among symbionts which were characterized by unique ecological strategies. Aposymbiotic octocoral recruits within high‐ and low‐light environments were inoculated with one of three Symbiodiniaceae species as monocultures or with cross‐paired mixtures, and we tracked symbiont uptake using quantitative genetic assays. Priority effects, in which early colonizers excluded competitive dominants, were evidenced under low light, but these early opportunistic species were later succeeded by competitive dominants. Under high light, a more consistent competitive hierarchy was established in which competitive dominants outgrew and limited the abundance of others. These findings provide insight into mechanisms of microbial community organization and symbiosis breakdown and recovery. Furthermore, transitions in competitive outcomes across spatial and temporal environmental variation may improve lifetime host fitness.

Hourly variation of environment and copepod community of the Ganges River Estuary of India: Perspectives on sampling estuarine zooplankton

High-resolution ecological databases are only rarely available for tropical estuaries, so details of their ecological variability are often poorly understood. We studied 12 h of continuous variability salinity, water temperature, pH, dissolved oxygen, NO3–N, and the copepod community (size > 200 μm) of the Ganges River Estuary (GRE) of India. We hypothesized that short-term environmental variability affects copepod community and its most and least abundant populations. We recorded twenty-nine copepod species, in terms of size the largest was Eucalanus elongatus (3.5–5 mm) and the smallest was Oithona brevicornis (0.4–0.51 mm). Spatial variability of the environment was not statistically significant. Site-specific temporal variability of salinity, water temperature, pH and dissolved oxygen was statistically significant but only a few of those variables affected the diversity and evenness of the copepod community. Bestiolina similis and Paracalanus parvus were among the most abundant and E. elongatus and Acrocalanus gibber were among the least abundant copepods of the GRE. Site-specific rank-abundance revealed that the numerical dominance of specific copepod changed within small (~500 m) spatial scale. Abundant copepods were mostly omnivores; a few large ones were carnivores whereas most others including the least abundant forms were herbivores. Population abundance of B. similis remained unaffected by temporal variability of environment. Compared to day time abundance of Paracalanus parvus increased in the dark and in relatively cooler waters showing evidence of its diel vertical movements. Abundance of E. elongatus increased in higher salinity, demonstrating its affinity towards the marine environment. Abundance of A. gibber showed significant temporal associations with different environmental variables. Variability exists within the copepod community in terms of diversity, abundance, size class, and feeding habits. For a better management of the ecological resources of this estuary we suggest not to overlook microscopic ecological changes of the lower trophic levels.

Interaction between damage and time-dependent deformation of mortar in concrete: 3D FE study at meso-scale

Creep of concrete can be partly attributed to the time-dependent deformation of cement paste and partly to the interaction between load-induced damage of mortar (hardened cement paste) and its non-elastic deformations [1]. The heterogeneity of concrete and related interaction between load-induced damage and non-elastic deformation of mortar can have significant influence on the long-term response of concrete. Some aspects of the problem have been investigated in [1] through 3D finite element (FE) analysis of a concrete cylinder at meso-scale. The concrete is treated as a bi-phase composite material, consisting of coarse aggregate and mortar matrix. The constitutive law for mortar is based on the microplane theory, while the aggregate is assumed to be linear elastic. The results obtained for basic creep and shrinkage, at different levels of applied uniaxial compressive load (both separate and combined action) are reported in [1]. This paper mainly focuses on the effect of cyclic variation of environmental temperature and its interaction with the load-induced damage, basic creep and shrinkage of mortar. It is shown that with higher loading level the increase of time deformation of concrete becomes progressive and the variation of environmental temperature strongly influences time-dependent concrete response.

LHAASO-WCDA time calibration using high-statistic low-energy cosmic rays

The Large High Altitude Air Shower Observatory (LHAASO) is a multi-component experiment to study cosmic ray physics, which is under construction near Mt. Haizishan (4410 m a.s.l.) in Southwest China. The 78,000 m2 Water Cherenkov Detector Array (WCDA), which is one of the main components of the LHAASO, will be able to survey the gamma-ray sky continuously in the energy range from 100 GeV to PeV. The precision of the time measurement in the detector cells of WCDA determines the sensitivity to the direction of gamma ray sources, necessitating a hardware calibration system to be deployed in the WCDA. Effects such as environment temperature variations will introduce time offsets between detector cells. In order to calibrate the time offset, a method using high-statistics low-energy cosmic rays has been developed. The detector cells are divided into clusters of 6×6 cells which are calibrated locally. This paper then describes the technique combining all the detector cells and demonstrates that the performance meets the requirements. The high-statistics of low-energy cosmic rays makes it possible to calibrate the detector in real time.

Global meta‐analysis reveals that invertebrate diversity is higher in permanent than in temporary lentic water bodies

Abstract One of the main constraints affecting invertebrate diversity in many freshwater lentic habitats is the presence of a dry phase which forces aquatic organisms to avoid this period through the migration to other water bodies or the production of resting stages. Field studies show contradictory results when comparing invertebrate diversity in permanent (PW) and temporary lentic waters (TW). Our objective was to test how diversity is influenced by the permanence of water in lentic habitats, and which factors affect the magnitude and direction of this difference, including sampling design. Through a systematic review, 66 publications were selected and classified according to the sampling design (spatial, temporal, and spatio‐temporal datasets). Meta‐analysis of the spatial dataset, which included 70% of the studies, revealed that diversity in PW was higher than in TW, and this difference was not influenced by annual precipitation, dispersal mode, habitat type or level of anthropogenic impact (proximity to urban or agricultural areas). We found a significantly higher effect size (PW greater than TW) when considering species richness rather than cumulative richness or Shannon diversity index, disconnected water bodies (hindering the exchange of individuals through water connection), organisms with passive dispersal (which cannot actively avoid the dry period), and study sites with high anthropogenic impact (where temporary habitats could undergo impacts; e.g. concentration of pollutants and eutrophication). We also found that the differences in diversity between PW and TW may decrease with increasing sampling effort. This result may be attributable to high species turnover due to the higher temporal environmental variation in TW relative to PW. Also, it indicates that sampling effort should be comparatively higher in TW to properly characterize the biodiversity in these environments in order to compare with PW. As global climate continues to change, our results suggest that loss in aquatic invertebrate diversity of TW will be likely to occur in regions where the frequency of drying events increases.

Transparent stretchable capacitive touch sensor grid using ionic liquid electrodes

Low cost soft, flexible and stretchable sensors are being explored that can be applied to virtually any surface, and promise to enable tactile sensing on robots, prosthetics, skin and stretchable displays. Previous work has shown that capacitive sensors that are both stretchable and transparent can be created by using ionically conductive hydrogel electrodes. In this study, the electrodes are interpenetrating polymer networks swollen with ionic liquid, enabling high transparency and stretchability, without evaporation. The interpenetrating network is synthesized from poly(ethylene oxide) and nitrile butadiene rubber. Electrodes are patterned using femtosecond laser machining, creating stretchable electrodes. These were encapsulated in a polydimethylsiloxane substrate, producing a 95% transparent sensor (450 nm). A 4x4 tactile array shows the ability to sense proximity and multi-touch, as well as be robust to variations in environmental temperature (from 4°C to 72°C). Temperature change has a large effect on the resistance of the electrodes — an effect that could be used to measure device temperature. In addition, the sensor is able to detect proximity and touch while on skin, when covered by a layer of fabric or during stretch.

Effect of elevated temperature variations on the corrosion resistance of S31603 and SS2562 austenitic stainless steels in chloride-sulphate environments

Effect of environmental temperature variation at 308K, 318K, 333K and 353K on the corrosion resistance of S31603 and SS2562 austenitic stainless steels in 2.5M H2SO4/3.5% NaCl solution was studied by potentiodynamic polarization, potentiostatic measurement and optical microscopy. S31603 exhibited higher general corrosion resistance compared to SS2562 with values of 0.529 mm/y and 8.701 mm/y (308K and 353K) compared to 0.911 mm/y and 17.492 mm/y for SS2562. The corrosion potential of SS2562 shifted to cathodic values compared to S31603 which varies between cathodic and anodic values. At 308K, SS2562 exhibited metastable pitting activity at potential of 0.02 V. Passivation occurs at 0.09 V before breakdown of the protective oxide. Beyond 308K, passivation was absent on SS2562. S31603 exhibited unstable passivation behaviour at 308K and elevated temperatures. The protective oxide of S31603 formed at certain potentials before collapsing at all temperatures studied. Images of both steels showed localized corrosion deterioration at the grain boundaries. Larger micro-pits were visible on SS2562 compared to S31603 which had numerous shallow pits on its surface. At 353K, the extent morphological deterioration has advanced further on SS2562 compared to S31603 with the grain boundaries becoming more visible. The microstructural deterioration on S31603 at 308K and 353K is comparatively minimal.

Complex and Diverse Drivers of Parasite Loads in a Cosmopolitan Insect

The goal of parasite epidemiologists is to understand the factors that determine host infection levels. Potential infection determinants exist at many scales, including spatial and temporal environmental variation, among-host differences, and interactions between symbionts infecting the same host. All of these factors can impact levels of parasitism, but frequently only a subset is considered in any host-parasite system. We examined several potential determinants of pinworm infection in wild Australian cockroaches (Periplaneta australasiae) from multiple biological scales: (1) habitat; (2) season; (3) cockroach body size, developmental stage, and sex; and (4) interactions between 2 pinworm species (Leidynema appendiculata and Thelastoma sp.). Over 1 yr, we collected 239 cockroaches from 2 separate rooms in an Illinois greenhouse. We used generalized linear mixed-effects models (GLMMs) to evaluate simultaneously the influence of these factors on pinworm abundance, and nearly all had significant effects. Overall, the abundance of L. appendiculata was greater than Thelastoma sp., but the relative abundance of the 2 species was reversed in each room (i.e., a taxon × habitat effect). Abundance varied over 4 trapping seasons and increased with cockroach size. Adult cockroaches had more pinworms than nymphs, and there was also a significant taxon × stage effect: adult cockroaches had fewer pinworms than expected for their larger size, and this reduction was greater in Thelastoma sp. than in L. appendiculata. Cockroach sex had no effect on infection. Although females had more worms than males, this difference could be explained by the larger size of females. Finally, after controlling for all other potential determinants of infection, we found a strong negative association between Thelastoma sp. and L. appendiculata; cockroaches tended to be infected with either 1 pinworm species or the other. Our work underscores the importance of measuring potential determinants of infection from as many scales as possible. Such approaches are necessary to unravel the complexities of host-parasite interactions.

Neighborhood effects explain increasing asynchronous seedling survival in a subtropical forest

Biotic interactions play a critical role in mediating community responses to temporal environmental variation, but the importance of these effects relative to the direct effects of environmental change remains poorly understood, particularly in diverse forest communities. Here we combine a neighborhood modeling approach with insights from coexistence theory to assess the effects of temporal variation in species interactions and environmental conditions (e.g., precipitation, temperature, and understory light availability) on seedling survival over nine census years in a subtropical forest. We find significant temporal shifts in the magnitude of neighborhood effects on both community-wide and species-level seedling survival (statistically significant random effects of neighborhood × year and neighborhood × species × year interactions). These results are consistent with the idea that environmental change will play a fundamental role on forest regeneration dynamics by altering biotic interactions at the neighborhood scale. Moreover, differences among species in response to neighbors over time contribute to a pattern of temporal decoupling of seedling survival between species, which can help to promote diversity in certain contexts. In separate analyses of multiple regression on distance matrices (MRM), altered interactions with neighbors are much stronger predictors of asynchronousseedling survival among species than the pure effects of climate and plant functional traits, explaining twice as much variation (43.9% vs. 22.2%). In sum, these results reveal that divergent species responses to interannual environmental variability detected are driven primarily by indirect effects mediated by changing biotic environments. This highlights the importance of including indirect effects from local biotic (neighborhood) interactions in forecasts of forest community responses to global change.

When water interacts with temperature: Ecological and evolutionary implications of thermo-hydroregulation in terrestrial ectotherms.

The regulation of body temperature (thermoregulation) and of water balance (defined here as hydroregulation) are key processes underlying ecological and evolutionary responses to climate fluctuations in wild animal populations. In terrestrial (or semiterrestrial) ectotherms, thermoregulation and hydroregulation closely interact and combined temperature and water constraints should directly influence individual performances. Although comparative physiologists traditionally investigate jointly water and temperature regulation, the ecological and evolutionary implications of these coupled processes have so far mostly been studied independently. Here, we revisit the concept of thermo‐hydroregulation to address the functional integration of body temperature and water balance regulation in terrestrial ectotherms. We demonstrate how thermo‐hydroregulation provides a framework to investigate functional adaptations to joint environmental variation in temperature and water availability, and potential physiological and/or behavioral conflicts between thermoregulation and hydroregulation. We extend the classical cost–benefit model of thermoregulation in ectotherms to highlight the adaptive evolution of optimal thermo‐hydroregulation strategies. Critical gaps in the parameterization of this conceptual optimality model and guidelines for future empirical research are discussed. We show that studies of thermo‐hydroregulation refine our mechanistic understanding of physiological and behavioral plasticity, and of the fundamental niche of the species. This is illustrated with relevant and recent examples of space use and dispersal, resource‐based trade‐offs, and life‐history tactics in insects, amphibians, and nonavian reptiles.

208 Molecular mechanisms through which heat stress compromises reproduction in pigs

Abstract Seasonal variations in environmental temperatures impose added stress on domestic species bred for economically important production traits. These heat-mediated stressors vary on a seasonal, daily, or spatial scale, and negatively impact behavior and reduce feed intake and growth rate, which inevitably leads to reduced herd productivity. The seasonal infertility observed in domestic swine is primarily characterized by depressed reproductive performance manifesting as delayed puberty onset, reduced farrowing rates, and extended weaning-to-estrus intervals. Understanding the effects of heat stress at the organismal, cellular, and molecular level is a prerequisite to identifying mitigation strategies that could reduce the economic burden of compromised reproduction. Additionally, hyperthermia experienced in utero influences industry-relevant postnatal phenotypes. Understanding tissue-specific molecular mechanisms through which heat stress confers suppressed reproductive ability is essential to the development of mitigation focused hypothesis driven solutions. This work was supported by the National Pork Board and the Iowa Pork Producers Association.

The high voltage system with pressure and temperature corrections for the novel MPGD-based photon detectors of COMPASS RICH-1

The novel MPGD-based photon detectors of COMPASS RICH-1 consist of large-size hybrid MPGDs with multi-layer architecture including two layers of Thick-GEMs and a bulk resistive MicroMegas. The top surface of the first THGEM is coated with a CsI film which also acts as photo-cathode. These detectors have been successfully in operation at COMPASS since 2016. Concerning bias-voltage supply, the Thick-GEMs are segmented in order to reduce the energy released in case of occasional discharges, while the MicroMegas anode is segmented into pads individually biased with positive voltage while the micromesh is grounded. In total, there are about ten different electrode types and more than 20000 electrodes supplied by more than 100 HV channels, where appropriate correlations among the applied voltages are required for the correct operation of the detectors. Therefore, a robust control system is mandatory, implemented by a custom designed software package, while commercial power supply units are used. This sophisticated control system allows to protect the detectors against errors by the operator, to monitor and log voltages and currents at 1 Hz rate, and automatically react to detector misbehaviour. In addition, a voltage compensation system has been developed to automatically adjust the biasing voltage according to environmental pressure and temperature variations, to achieve constant gain over time. This development answers to a more general need. In fact, voltage compensation is always a requirement for the stability of gaseous detectors and its need is enhanced in multi-layer ones. In this paper, the HV system and its performance are described in details, as well as the stability of the novel MPGD-based photon detectors during the physics data taking at COMPASS.

Removal of temperature effect in impedance-based damage detection using the cointegration method

Electromechanical impedance technique has been widely used in the area of structural health monitoring. However, both damage and variation in environmental temperature can cause the changes in electromechanical impedance signature, which may cause false damage diagnosis. The temperature effect on the electromechanical impedance-based method has been one of its main drawbacks in practical application. This article proposes a new approach based on cointegration to eliminate temperature interference in the electromechanical impedance technique. The augmented Dickey–Fuller test is used to analyze the stationary characteristics of the time series and determine the degree of non-stationarity. The Johansen test is used to obtain the cointegrating residuals instead of the direct electromechanical impedance responses for damage detection. The proposed method is verified on the undamaged and damaged steel plates with the consideration of environmental temperature variations. The damage detection was based on the electromechanical impedance technique in which the peak frequency is chosen as a cointegrated variable. The experimental results show that the cointegration method can remove the temperature effect on the electromechanical impedance responses, and the cointegrating residuals are effective indices to indicate the occurrence of damage.

Seasonal and annual variations in egg mass and clutch size for Loggerhead Sea Turtles (Caretta caretta): experienced females lay heavier eggs

Organisms modify reproductive traits adaptively or non-adaptively in response to temporal environmental variation. Long-lived iteroparous sea turtles are ideal animals to examine such temporal shifts in resource allocation. We analyzed seasonal shifts in egg mass and clutch size for Loggerhead Sea Turtles (Caretta caretta (Linnaeus, 1758)) nesting at a temperate rookery (Yakushima Island, Japan) over a 2-year period, as well as annual variation in egg mass and clutch size over a 5-year period. Egg mass and clutch size, adjusted for female body size, did not vary seasonally at both the population and individual levels. Adjusted egg mass showed significant annual variation, despite a lack of annual variation in adjusted clutch size. Thus, Loggerhead Sea Turtles are unlikely to exhibit adaptive seasonal variation in reproductive traits, whereas they vary egg size non-adaptively in response to annual environmental conditions. Although experienced Loggerhead Sea Turtles laid heavier eggs, the annual variation in egg mass was not attributable either to breeding experience of the sampled females or to ambient temperature during follicular development, implying that other factors are involved, such as resource availability. Our data show that egg size is a more plastic reproductive trait than clutch size for Loggerhead Sea Turtles inhabiting the North Pacific.

The effect of thermal pre-incubation and exposure on sensitivity of zebrafish (Danio rerio) to copper and cadmium single and binary exposures

Zebrafish (Danio rerio) is a prominent model organism in a wide range of biological studies including toxicology. However, toxicological studies are often performed at species specific optimum temperature, and knowledge on the effect of different temperature regimes on the toxicity of metal ions is rather limited. To address this knowledge gap, present study investigates the effect of various thermal scenarios (simultaneous and sequential; acute and chronic) on the toxicity of Cu and Cd in zebrafish. For this purpose we assessed mortality and whole body metal burdens as indicators of toxicity and bioavailability, respectively, and whole body electrolyte concentrations and body condition as the indicators of physiological condition. Thermal pre-incubations (for 12 or 96 h or 28 days) and subsequent metal ion exposures (for 10 days) were conducted at 17, 22, 25, 28, 32 and 34 °C. The metal exposures were performed at Cu concentrations of 1.2 μM and Cd concentrations of 0.2 μM, both singly and in binary mixtures. Irrespective of thermal treatments, Cu exposures resulted in greater mortality than Cd exposures at the given concentrations. Moreover, the Cu and Cd mixture indicated a synergistic effect. While acute pre-incubation for 12 or 96 h at elevated temperatures increased mortality in the subsequent metal exposure at the optimum temperature (28 °C), pre-incubation at cold temperatures in this scenario appeared to increase tolerance towards the subsequent metal exposure. Chronic thermal pre-incubation of zebrafish to a range of temperatures for 28 days moderated the effect of temperature fluctuations on subsequent metal toxicity at the optimum temperature. Chronic thermal pre-incubation at a range of temperatures followed by metal exposure at the same temperature showed that environmental temperature variations (higher or lower than optimal temperature) coupled with metal exposure, led to increased mortality, furthermore, the highest whole body metal burdens were measured in this scenario. Nevertheless, neither the whole body burden of metals, nor the metal accumulation rate, were predictors of mortality, i.e. these two values were not higher in dead fish in comparison to those that survived the exposures. Finally, we observed a significant decrease in the whole body Na+ level of dead fish in comparison to fish which survived the exposure conditions, suggesting that survival depends on maintaining Na+ homeostasis under the applied multi-stress conditions. Overall, our results show that thermal pre-history and ambient temperature play an important role in determining the tolerance of zebrafish towards metal ion stress.

Environmental temperature variation affects brain protein expression and cognitive abilities in adult zebrafish (Danio rerio): A proteomic and behavioural study

Water temperature is an important environmental parameter influencing the distribution and the health of fishes and it plays a central role in ectothermic animals. The aim of this study is to determine the effects of environmental temperature on the brain proteome and the behavioural responses in zebrafish, a widely used animal model for environmental “omics” studies. Adult specimens of wild-type zebrafish were kept at 18 °C, 34 °C and 26 °C (control) for 21 days. Proteomic data revealed that several proteins involved in cytoskeletal organization, mitochondrial regulation and energy metabolism are differently regulated at the extreme temperatures. In particular, the expression of proteins associated to synapses and neurotransmitter release is down-regulated at 18 °C and 34 °C. In both thermal conditions, fish exhibited a reduced interest for the novel environment and an impairment of cognitive abilities during Y-Maze behavioural tests. The observed pathways of protein expression are possibly associated to functional alterations of the synaptic transmission that may result in cognitive functions impairment at central nervous system level as those revealed by behavioural tests. This study indicates that temperature variations can elicit biochemical changes that may affect fish health and behaviour. This combined approach provides insights into mechanisms supporting thermal acclimation and plasticity in fishes. SignificanceEnvironmental temperature variation may impact on all levels of biological life. Understanding the impact of thermal variation on the nervous system and animal behaviour is of primary importance since the results obtained can be applied from the ecological to the biomedical fields.