Genetic components in a thermal developmental plasticity of the beetle Tribolium castaneum.

Low developmental temperatures cause ectotherms to retard growth, postpone maturation, and emerge at either larger or smaller adult size. In this study, we explored how these thermal responses evolved, focusing on their genetic basis. We applied a full diallel breeding design on inbred lines of the flour beetle, Tribolium castaneum. To assess the proportional contributions of genetic and non-genetic effects, each genotype, a unique combination of parental haplotypes, was reared from an egg to imago at five developmental temperatures. Faster development of females vs. males was associated with comparatively larger body masses of females (pupae and imago). In contrast, the rapid development caused by warmer environments resulted in smaller beetles (pupae and imago), but there were significant differences in this trait among genotypes. Independent effects of parental haplotypes played the major role in explaining the variance of body mass, but interactive effects of parental haplotypes explained most of the variance in developmental length. Genotypes responded to the thermal environment in a markedly uniform way. Nevertheless, we found the low statistically significant variance in the slopes of thermal reaction norms for body mass and developmental, which was mainly driven by the interactive effects of parental haplotypes. Overall, the thermal plasticity of T. castaneum follows the most common pattern among ectotherms, the so-called temperature-size rule. Detection of the low genetic variance in the shape of this response supports the idea that thermal developmental plasticity remains under a strong selective pressure in ectotherms.

Left ventricular end-diastole hemodynamics is strongly associated with spontaneous cardiac baroreflex in humans.

BACKGROUND: In animals, hemodynamic conditions during left ventricular (LV) end-diastole are crucial for the excitation of autonomic afferents distributed throughout cardiac chambers and large thoracic vessels. The objective of the study was to select the echocardiographic indices of LV diastolic function that are the most potent predictors of the heart's spontaneous baroreflex in humans. METHODS: In 47 untreated hypertensive patients (26 with normal and 21 with increased left atrium diameter) and 24 healthy controls, baroreflex sensitivity (BRS) was assessed in the low (αLF; 0.04-0.15 Hz) and high frequency (αHF; 0.15-0.4 Hz) components in the supine and during tilting. The [Formula: see text] normalized to LV end-diastolic diameter (the [Formula: see text] index) is a marker of the septum late diastolic distension rate ([Formula: see text] denotes peak late diastolic velocity at the septal mitral annulus) under the corresponding transmitral pressure gradient that determines the peak velocity of blood flow (A) into the LV chamber. RESULTS: The [Formula: see text] markedly stronger than [Formula: see text] ratio correlated with the BRS. In the best-fit models of multivariable linear regression, the [Formula: see text] index was the independent predictor of the αLF BRS at tilting (ß = -0.3; p = 0.01). Independent of clinical and echocardiographic parameters, the [Formula: see text] index predicted also both the αHF BRS in the supine position (ß = -0.23; p = 0.01) and the αHF BRS reinforcement due to increased preload (ß = -0.28; p = 0.001). CONCLUSIONS: The [Formula: see text] index is a reliable marker of diastolic dysfunction that evokes significant heart's baroreflex impairment and is markedly stronger than [Formula: see text] ratio associated with these systemic consequences of altered LV diastole hemodynamics.

Does temperature and oxygen affect duration of intramarsupial development and juvenile growth in the terrestrial isopod Porcellioscaber (Crustacea, Malacostraca)?

According to the temperature-size rule (TSR), ectotherms developing under cold conditions experience slower growth as juveniles but reach a larger size at maturity. Whether temperature alone causes this phenomenon is unknown, but oxygen limitation can play a role in the temperature-size relationship. Oxygen may become limited under warm conditions when the resulting higher metabolism creates a greater demand for oxygen, especially in larger individuals. We examined the independent effects of oxygen concentration (10% and 22% O2) and temperature (15 °C and 22 °C) on duration of ontogenic development, which takes place within the maternal brood pouch (marsupium), and juvenile growth in the terrestrial isopod common rough woodlouse (Porcellioscaber). Individuals inside the marsupium undergo the change from the aqueous to the gaseous environment. Under hypoxia, woodlice hatched from the marsupium sooner, but their subsequent growth was not affected by the level of oxygen. Marsupial development and juvenile growth were almost three times slower at low temperature, and marsupial development was longer in larger females but only in the cold treatment. These results show that temperature and oxygen are important ecological factors affecting developmental time and that the strength of the effect likely depends on the availability of oxygen in the environment.

Population growth rate and genetic variability of small and large populations of Red flour beetle (Tribolium castaneum) following multigenerational exposure to copper.

We reared large (1000 individuals) and small (20 individuals) populations of Tribolium castaneum on diet contaminated with copper in order to determine if the size of a population affects its ability to adapt to adverse environmental conditions. After 10 generations, we used microsatellite markers to estimate and subsequently compare the genetic variability of the copper-treated populations with that of the control populations, which were reared on uncontaminated medium. Additionally, we conducted a full cross-factorial experiment which evaluated the effects of 10 generations of "pre-exposure" to copper on a population's fitness in control and copper-contaminated environments. In order to distinguish results potentially arising from genetic adaptation from those due to non-genetic effects associated to parental exposure to copper, we subjected also F11 generation, originating from parents not exposed to copper, to the same cross-factorial experiment. The effects of long-term exposure to copper depended on population size: the growth rates of small populations that were pre-exposed to copper were inhibited compared to those of small populations reared in uncontaminated environments. Large Cu-exposed populations had a higher growth rate in the F10 generation compared to the control groups, while the growth rate of the F11 generation was unaffected by copper exposure history. The only factor that had a significant effect on genetic variability was population size, but this was to be expected given the large difference in the number of individuals between large and small populations. Neither copper contamination nor its interaction with population size affected the number of microsatellite alleles retained in the F10 generation.

Comparison of sinoatrial conduction time measured by Holter method and premature stimulation method.

BACKGROUND: The reliability of noninvasive Holter method for the calculation of sinoatrial conduction time (SACT) has not been confirmed by results of invasive electrophysiological studies of sinus nodal function. The aim of this study was to compare the values of SACT obtained by Holter method with values estimated by premature atrial stimulation method. METHODS: The study population consisted of 61 patients, in whom the 24-hour ambulatory ECG monitoring had shown the occurrence of atrial premature beats. All these subjects were undergoing electrophysiological study including programmed atrial and ventricular stimulation. The measurements of SACT were obtained using spontaneous atrial premature beats (Holter method) and high right atrial stimulation (Strauss method). RESULTS: There was a good correlation between measurements of SACT by Holter method and Strauss method (r = 0.79; P < 0.001). There was no significant difference between values of SACT estimated by two compared methods. However, in certain patients, there were appreciable differences and SACT measured using spontaneous premature beats was shorter in 34 and longer in 23 patients than that estimated by the Strauss method. The values of SACT calculated by Holter method and Strauss method were significantly (P < 0.001) higher in patients with sick sinus syndrome than in those without evidence of sinus node dysfunction. CONCLUSIONS: Good correlation between values of SACT obtained by two compared methods suggests that single measurement performed using Holter method may be adequate for reliable calculation of SACT.

Response of Tribolium castaneum to elevated copper concentrations is influenced by history of metal exposure, sex-specific defences, and infection by the parasite Steinernema feltiae.

We studied how copper toxicity in the red flour beetle, Tribolium castaneum changed as a result of infection by the entomopathogenic nematode Steinernema feltiae. Measured traits were: respiration, growth and survival, as well as the concentrations of copper within beetle tissues and in its diet. By comparing F1 and F5 generation we were able to answer how long-term metal exposure changed the responses to both copper and the parasite. The beetles did accumulate copper; however, the results indicated that copper concentrations in beetle tissues were affected by nematode infection, the sex of the experimental animals, and the number of generations of exposure. Five generations of exposure to copper resulted in the highest dry body mass of infected beetles of both sexes; additionally, this group also had the lowest copper concentrations in their tissues. The only factor that had a significant effect on respiration was infection by nematodes: infected beetles of both sexes in both generational groups had significantly decreased respiration rates. Survival was lowest in nematode-infected animals of both sexes from both generations, regardless of exposure to copper. Our results confirm that an organism's response to metal pollution is dependent on its health status and sex. We also found that the history of exposure to metal was equally important-we found enhanced resistance to copper intoxication after only five generations of exposure.

Complex response in size-related traits of bulb mites (Rhizoglyphus robini) under elevated thermal conditions - an experimental evolution approach.

Temperature is a key environmental factor affecting almost all aspects of life history in ectotherms. Theory predicts that they grow faster, reach smaller sizes and produce smaller offspring when temperature increases. In addition, temperature changes, through their effects on metabolism, may also influence the expression of alternative reproductive phenotypes (ARPs) in ectotherms. Although many studies have investigated the phenotypic plasticity of life history traits in relation to temperature change, little is known about how those traits and phenotypic plasticity may evolve together. In our study we subjected bulb mites (non-model, soil organisms that normally experience rather stable thermal conditions) to experimental evolution in two temperature treatments: control (24°C) and elevated (28°C). After 18 generations, we measured adult body size, egg size and development time of both treatments at control as well as at elevated temperatures (test temperatures). Thus, we were able to detect genetic changes (the effects of selection temperature) and environmental effects (the effects of test temperature). We also observed the ARP expression throughout the experimental evolution. Our results revealed quite complex patterns of life history in traits response to temperature. Mites developed faster and reached smaller sizes at increased temperature, but evolutionary responses to increased temperature were not always parallel to the observed phenotypic plasticity. Additionally, despite smaller body sizes, females laid larger eggs at higher temperature. This effect was more pronounced in animals evolving at elevated temperature. Evolution at increased temperature also affected ARP expression, with the proportion of armored fighters decreasing from generation to generation. We propose that this could be the consequence of temperature sensitivity of the cost-to-benefits ratio of expressing ARPs.

Interactions between toxic chemicals and natural environmental factors--a meta-analysis and case studies.

The paper addresses problems arising from effects of natural environmental factors on toxicity of pollutants to organisms. Most studies on interactions between toxicants and natural factors, including those completed in the EU project NoMiracle (Novel Methods for Integrated Risk Assessment of Cumulative Stressors in Europe) described herein, showed that effects of toxic chemicals on organisms can differ vastly depending purely on external conditions. We compiled data from 61 studies on effects of temperature, moisture and dissolved oxygen on toxicity of a range of chemicals representing pesticides, polycyclic aromatic hydrocarbons, plant protection products of bacterial origin and trace metals. In 62.3% cases significant interactions (p< or =0.05 or less) between natural factors and chemicals were found, reaching 100% for the effect of dissolved oxygen on toxicity of waterborne chemicals. The meta-analysis of the 61 studies showed that the null hypothesis assuming no interactions between toxic chemicals and natural environmental factors should be rejected at p=2.7 x 10(-82) (truncated product method probability). In a few cases of more complex experimental designs, also second-order interactions were found, indicating that natural factors can modify interactions among chemicals. Such data emphasize the necessity of including information on natural factors and their variation in time and across geographic regions in ecological risk assessment. This can be done only if appropriate ecotoxicological test designs are used, in which test organisms are exposed to toxicants at a range of environmental conditions. We advocate designing such tests for the second-tier ecological risk assessment procedures.

Interactions between effects of environmental chemicals and natural stressors: a review.

Ecotoxicological effect studies often expose test organisms under optimal environmental conditions. However, organisms in their natural settings rarely experience optimal conditions. On the contrary, during most of their lifetime they are forced to cope with sub-optimal conditions and occasionally with severe environmental stress. Interactions between the effects of a natural stressor and a toxicant can sometimes result in greater effects than expected from either of the stress types alone. The aim of the present review is to provide a synthesis of existing knowledge on the interactions between effects of "natural" and chemical (anthropogenic) stressors. More than 150 studies were evaluated covering stressors including heat, cold, desiccation, oxygen depletion, pathogens and immunomodulatory factors combined with a variety of environmental pollutants. This evaluation revealed that synergistic interactions between the effects of various natural stressors and toxicants are not uncommon phenomena. Thus, synergistic interactions were reported in more than 50% of the available studies on these interactions. Antagonistic interactions were also detected, but in fewer cases. Interestingly, about 70% of the tested chemicals were found to compromise the immune system of humans as judged from studies on human cell lines. The challenge for future studies will therefore be to include aspects of combined stressors in effect and risk assessment of chemicals in the environment.

Combined effect of environmental pollutants (nickel, chlorpyrifos) and temperature on the ground beetle, Pterostichus oblongopunctatus (Coleoptera: Carabidae).

Terrestrial organisms in the field often are exposed to a combination of stress factors of various origins, but little is known about interactions between different types of stressors. In the present study, we demonstrate the results of a study on interactions between Ni, chlorpyrifos (CPF), and temperature in the ground beetle, Pterostichus oblongopunctatus. The results revealed that all factors, and their interactions, influenced life-cycle parameters of the beetles (survival and reproduction). Significant three-factor interactions were found for effects on beetle survival, indicating that the combined negative effect of Ni and CPF was temperature dependent. In addition, significant effects of body mass were found: The survival of beetles treated with CPF and the reproduction of beetles exposed to Ni were positively correlated with body mass. All studied endpoints were affected by temperature. The results indicate that understanding interactions between temperature and toxicants, as well as among chemicals themselves, is essential for proper ecological risk assessment.

Increased response to cadmium and Bacillus thuringiensis maize toxicity in the snail Helix aspersa infected by the nematode Phasmarhabditis hermaphrodita.

To determine the effect of nematode infection on the response of snails to selected toxins, we infected Helix aspersa with 0-, 0.25-, 1-, or 4-fold the recommended field dose of a commercial nematode application for agricultural use. In the first experiment, the snails also were exposed to cadmium via food and soil at concentrations of 0, 30, 60, 120, or 240 mg/kg in a full-factorial design. In the second experiment, snails were infected with nematodes and also fed either Bt (expressing Bacillus thuringiensis toxin) maize or non-Bt maize. The snails were weighed at the beginning and end (after four weeks) of the experiments, and mortality was checked daily. Neither exposure of snails to nematodes nor exposure of snails to cadmium or Bt toxin affected the survival rates of snails. The number of dead snails was highest for combinations of nematode treatments with cadmium concentrations of 120 and 240 mg/kg. In both experiments (Bt and cadmium), the growth rate decreased with increasing nematode dose. The Bt maize was not harmful to the snails in the absence of nematodes, but infected snails grew faster when fed non-Bt maize. The growth rate of snails exposed to cadmium decreased with exposure to increasing Cd concentrations and differed significantly between the no-nematode treatment and the treatments with nematode doses of one- and fourfold the recommended field dose. Snails treated with the highest dose of nematodes accumulated the highest cadmium concentrations.

Effect of interaction between density dependence and toxicant exposure on population growth rate of the potworm Enchytraeus doerjesi.

Laboratory cultures of the potworm Enchytreaus doerjesi were exposed to zinc-contaminated soil at nominal concentrations 0, 75, 150, 300, or 600 mg Zn/kg dry weight for four weeks (one generation) at five different initial densities (5, 10, 20, 40, or 80 individuals per 20 g soil). The final culture numbers and the instantaneous population growth rate, r(i) were used as measures of culture response to both factors. In all treatments, the number of individuals increased during the experiment; thus, all the cultures exhibited positive r(i) values. The population growth rates decreased significantly with increasing Zn concentration and were also affected by the initial density. However, the latter effect was nonlinear and the initial density of 20 individuals resulted in the highest r(i) values throughout the whole range of Zn concentrations tested, while the lowest population growth rates were recorded for the highest initial density. Significant interaction between zinc toxicity and population size was found for the two lowest initial densities, where synergistic effects were noted. No effect of density on zinc toxicity was found at initial densities of 20 to 80 individuals, most probably because the animals were fed ad libitum and thus were not food limited.

The respiration rate of the beet armyworm pupae (Spodoptera exigua) after multi-generation intoxication with cadmium and zinc.

The beet armyworm (Spodoptera exigua) were fed on artificial food contaminated with zinc (200 mg kg(-1) dry mass) or cadmium (66 mg kg(-1) dry mass) for 15 generations. In 15th generation, O2 output and CO2 production of pupae were measured. Exposure to cadmium did not cause any effects whilst exposure to zinc led to a significant increase in the respiration rate of pupae. The average respiratory quotient (RQ) did not differ between treatments (ca. 0.7).

Activity of carboxylesterase and glutathione S-transferase in different life-stages of carabid beetle (Poecilus cupreus) exposed to toxic metal concentrations.

Among the cytoplasmatic enzymes responsible for neutralization of organic xenobiotics, carboxylesterases (CarE) and glutathione S-transferases (GST) play important roles. Our study tested to what extent dietary Zn or Cd could modify the activity of CarE and GST at different life-stages of the carabid beetle Poecilus cupreus. Treatment and stage effects generally were statistically significant. For CarE activity in the beetles exposed to cadmium, only treatment was a significant factor. In all cases, the interaction between studied factors was statistically significant, implying that the physiological condition of the animals may enhance or reduce enzyme activity. We also observed differences between animals treated with cadmium and zinc in the pattern of enzyme activity, and a difference in GST activity measured with two different substrates. Our results confirmed that in studying enzyme activity under metal stress one should consider the animal's life-stage and sex.

Effects of cadmium and zinc on larval growth and survival in the ground beetle, Pterostichus oblongopunctatus.

Carabid beetles, like Pterostichus oblongopunctatus, living in metal contaminated areas may be exposed to elevated levels of metals within their diets. However, when compared to other second order consumers, they have one of the lowest observed levels of metals, indicating methods of detoxification to deal with such toxicants. In this study, we investigated if chronic, multigenerational exposure to metals leads to resistance to toxic metal concentrations, and if so, what are the costs associated with them. Adult organisms were collected from two sites, a polluted and a reference site near Olkusz, in southern Poland. These adults were immediately mated, and eggs were collected twice weekly to assess the effects in the larvae of the F(1) generation. Larvae were randomly exposed to one of four artificial mediums: control, 50 mg kg(-1) Cd, 500 mg kg(-1) Zn, and a combined treatment of 50 mg kg(-1) Cd and 500 mg kg(-1) Zn to investigate possible interactions. Individuals were sacrificed at 10, 30, and 40 days. Although metals were not accumulated in larvae (p>0.05), larvae fed the Cd or the Zn treatment grew significantly slower, and had the lowest survival rate (p<0.05) in respect to control. Out of metal treated animals, those on the combined treatment of CdZn grew the quickest and had the highest observed survival (p<0.05). Although previous studies have demonstrated changes in adult population parameters under chronic, multigeneration exposure to toxic metal concentrations, our study did not reveal any changes in the larval stage.

Decreased energetic reserves, morphological changes and accumulation of metals in carabid beetles (Poecilus cupreus L.) exposed to zinc- or cadmium-contaminated food.

The prime objective of the study was to find out whether contamination of food with metals affects body size, energetic reserves and developmental instability in ground beetles (Poecilus cupreus L.: Carabidae). The transfer of Cadmium (Cd) and Zinc (Zn) from medium (nominal concentrations in the medium: 0, 40, 160, 640 or 800 mg kg(-1) for Cd and 0, 400, 1600 or 6400 mg kg(-1) for Zn) to housefly larvae to beetles was also studied. Feeding the beetles throughout their entire lifetime with Cd-contaminated housefly pupae resulted in a significant decrease in body caloric value and the size of the elytrae, tibiae and rear femora. Although body mass also decreased with increasing Cd concentration, this effect was non-significant due to large variance in all treatments. Similar trends were also found in beetles fed pupae contaminated with Zn, but the effect on body mass and caloric value was non-significant. Zn exerted significant effects only on the size of the elytrae, middle and rear tibiae, and front and rear femora. No effect on fluctuating asymmetry (FA) was found in Cd- or Zn-treated beetles. The results indicate that ground beetles exposed to metal-contaminated food have lower amounts of energy available, which may be reflected in lower energetic reserves and changed body growth. However, the metals do not cause developmental instability in the carabids studied, at least not in the first generation. The concentrations of Zn were efficiently regulated in carabids, resulting in only minor differences between the beetles exposed to different Zn treatments. In contrast, Cd accumulated both in the housefly and the beetles, and the concentrations increased significantly with increasing medium contamination level.