Variable predation risk and the dynamic nature of mosquito antipredator responses to chemical alarm cues

Summary. Predation is a pervasive selective agent highly variable in space and time. Due to the costs associated with antipredator responses, prey would be at a selective advantage if they respond to predation threats with an intensitfy matching the threat posed by the predator. Many aquatic organisms have been shown to use chemical alarm cues present in the water to assess the level of risk in their environment. This includes mosquito larvae which show antipredator responses to conspecific alarm cues. In this study, we investigated the nature of the responses of larval mosquitoes Culex restuans to those cues. In our initial observations, we showed pond/population differences in the response intensity of C. restuans to alarm cues. In experiment 1, we showed that the response intensity to alarm cues could be increased by increasing the background level of risk in the mosquitoes’ environment (by adding salamander predators) and once turned on, the response intensity to alarm cues was likely maintained for the remainder of the mosquitoes’ aquatic life. In experiments 2 and 3, we investigated if the increase in response intensity to alarm cues was directly correlated with the level of background risk in the mosquitoes’ environment. When given increasing levels of background risk, mosquito larvae subsequently showed a graded response to conspecific alarm cues. This series of experiments demonstrates that the response intensity of larval mosquitoes to a standard concentration of alarm cues is not fixed, but rather dependent on the background level of risk in the environment. An understanding of the background level of risk is particularly important for comparing antipredator responses of prey between habitats.     

Locomotor kinematics and behaviour in the escape response of European sea bass, Dicentrarchus labrax L., exposed to hypoxia

To assess the effect of oxygen reduction on the escape response of sea bass, Dicentrarchus labrax, an integrative experimental approach was employed. The effect of hypoxia was tested on locomotor variables, i.e. cumulative distance (D), maximum swimming speed (V _max) and maximum acceleration (A _max). Behavioural variables, such as responsiveness (i.e. the proportion of individuals responding out of the total number of fish tested), response latency (i.e. the time interval between stimulus onset and the first detectable movement leading to the escape of the animal) and directionality (i.e. the proportion of escape responses in which the first detectable movement of the head was oriented away or towards the stimulus at its onset) were also considered. Four levels of oxygen were used: >85% (i.e. normoxia, the control treatment), 50, 20 and 10% of air saturation. Sea bass responsiveness decreased significantly at 10% of air saturation, while hypoxia did not have any effect on the response latency. At the onset of the escape response, the proportion of away/towards responses was random when oxygen was ≤50% of air saturation, suggesting an impairment of the left–right discrimination. Whatever the level of hypoxia, none of the locomotor variables (i.e. D, V _max and A _max) was significantly different from normoxia. Our study suggests that hypoxia may reduce sea bass elusiveness facing a predator by directly affecting its escape behaviour, possibly related to an impairment of the mechano-sensory performance and/or in the Mauthner cells involved in triggering the escape response.     

Search or relax: the case of bachelor wood bison

Summary Males of gregarious species of mammals often do not associate with female groups during the breeding season. Such males could leave groups either to search for new breeding opportunities, or to restore body condition before rejoining new female groups. To investigate these two competing hypotheses, we studied the chronology of male wood bison (Bison bison athabascae) associating with females, and their aggressive and sexual behaviour over two breeding seasons. With increasing age, males were more often solitary, were more involved in aggressive interactions, investigated the genitals of females more frequently, and tended females more often. Group size did not affect whether or not males joined or left groups. The presence of oestrous females in a group did not affect the number of bulls in that group, and did not affect the joining or leaving of males. Older, dominant males did not exclude younger ones from female groups. Males observed outside female groups spent relatively more time feeding and resting than bulls in groups. Changes in group composition experienced by a male often involved the joining or splitting of female groups, as opposed to actual transfer of males between groups. Our results suggest that males leave female groups in order to recover, not for the purpose of searching for new female groups. We argue that due to the fluidity of wood bison groups, it is possible for a male to encounter new females even when remaining in a female group. Correspondence to: P.E. Komers     

Fenarimol solar degradation pathways and photoproducts in aqueous solution

The degradation photoproducts of the fungicide fenarimol obtained from irradiation of aqueous solutions with sunlight were characterised. The photoproducts resulting from samples with different exposure times were extracted and separated using chromatographic techniques. Seven main photoproducts were detected using high performance liquid chromatography with a photodiode array detector, gas chromatography with mass spectrometry detector and Fourier transform infrared spectroscopy. Structures are suggested for possible photoproducts based on the characterisation results, minimum energy geometry of the parent compound, and the mass spectral behaviour of fenarimol. These correspond to the compounds with m/z 328 (three structural isomers (a), (b) and (c)), m/z 294 (two structural isomers (a) and (b)), m/z 292, 278 and 190. Of the various major products detected, the isomer 328(a) is seen to be particularly unstable under the action of sunlight. The most stable photoproducts are found to be those with m/z 294(a), 278 and 190. However, upon prolonged solar irradiation all of these break down to produce polar, low molecular weight compounds. Comparison with our own and other results on fenarimol photolysis indicate significant solvent effects on the process. The combination of these structural characterisation results and previous data from spectroscopic and photodegradation kinetics studies allows us to suggest some possible mechanisms for the photodegradation of fenarimol under sunlight.     

Investigation of acute toxicity of fenitrothion on peppered corydoras (Corydoras paleatus) (Jenyns, 1842)

Fenitrothion, as an organophosphothionate insecticide, is a contact insecticide and selective acaricide, also used as a vector control agent for malaria in public health programs. A 96 h LC50 value of fenitrothion, a potential toxic pollutant contaminating aquatic ecosystems, was determined on the adult peppered corydoras (Corydoras paleatus). The experiments were repeated three times. The static test method of acute toxicity test was used. Water temperature was regulated at 23 +/- 1 degrees C. In addition, behavioral changes at each fenitrothion concentration were observed for the individual fish. Data obtained from acute toxicity tests were evaluated using the Probit Analysis Statistical Method. The 96 h LC50 value for peppered corydoras was estimated as 3.51 mg/l.     

A single chorionic gonadotropin assay for maternal serum screening for Down's syndrome

A simple enzyme immunoassay measuring human chorionic gonadotropin in undiluted maternal serum has been developed in order to be used as a prenatal screening test for Down' s syndrome. A retrospective study of maternal serum sampled during pregnancies associated with trisomy 21 shows that with a 5% amniocentesis rate determined on a single test, the detection rate of trisomy 21 would be around two-thirds of the affected pregnancies. A prospective study of 9040 pregnant women under 38 years has confirmed the usefulness of the assay.     

SO2 modeling in İzmit Gulf, Turkey during the winter of 1997: 3 cases

In this study, SO₂ dispersion over İzmit Gulf is simulated by California Puff (CALPUFF) model for three air pollution cases, which occurred on January 28, February 12, and February 26, 1997. These days are generally characterized by dominant high-pressure systems – pressure values reaching 1032 mb, low wind speeds and sometimes calm conditions, and low temperatures with a minimum of 0°C. Hourly simulations during those critical cases were carried out and results revealed very high concentrations of SO₂ transported to the downwind regions of Tüpraş and Gebze, and values sometimes exceeded 1,000 μg/m³. Nighttime and morning simulations associated with inversion produced considerably higher values of SO₂ than the afternoon simulations associated with breeze. Model verification was conducted by comparing the measured daily average values of eight stations with the model predicted values at the same receptor points. Results showed that the model well predicted the values at station Gebze in all three cases. The model sometimes underestimated and sometimes overestimated the concentrations at other receptor stations.     

The politics of interbasin transfers: socio‐environmental impacts and actor strategies in Tunisia

Mediterranean wetlands are of key interest in the preservation of biodiversity. However, their ecological water requirement is in constant competition with human uses, particularly in a context of aridity and climate change. This paper examines the case of the Ichkeul Lake‐Lagoon system located in the north of Tunisia in a river basin that is heavily contributing to the water supply of southern regions through water transfers. It maps out the various actors involved, their stakes, discourses and strategies, and explains the current degradation of the Ichkeul system by unpacking the decision‐making power of these actors. It confirms that marginal social groups, ecosystems and next generations are the main parties affected by current water allocation patterns.     

Predominance of alcohol and illicit drugs among traffic accidents fatalities in an urban area of Brazil

Objective: The objective of this study was to determine the prevalence of alcohol and illicit drug use among victims of fatal traffic accidents in the Metropolitan Region of Vitória, Brazil, during the period 2011–2012.

Methods: Blood samples were collected and analyzed for the presence of drugs from 391 deceased victims of traffic crashes that occurred in the Metropolitan Region of Vitória, Brazil. The victims included drivers, passengers, and pedestrians. Sociodemographic variables such as age, gender, day of the week, and period of the year in which the accidents occurred were recorded. The analyses were performed by a gas chromatography–flame ionization method for alcohol and by a gas chromatography–mass spectrometry for amphetamines, cocaine, and cannabis.

Results: The results showed that 44.8% (n = 175) of all cases were positive for alcohol and/or illicit drugs. The detection of alcohol and/or drugs was more frequent in young males, aged 17 to 34, whose samples were positive in 46.8% of cases. Small differences among drivers, passengers, and pedestrians were observed (drivers = 45.9%, passengers = 46.4%, and pedestrians = 45.6%). In general, the most prevalent drug was alcohol, with 141 positive cases (36.1%), followed by cocaine, with 47 positive cases (12%). Amphetamines and cannabis had positivity rates of 4.1 and 4.3%, with 16 and 17 positive cases, respectively. The combined use of alcohol and other drugs was found in 36 cases (9.2%). Crack cocaine use was observed in 27.7% of the positive cases for cocaine.

Conclusions: For the effective reduction of traffic accidents related to driving under influence of drugs (DUID), we suggest the intensification of enforcement actions against the use of alcohol by drivers, the definition of which illicit drugs should be surveyed, as well the cutoff values, the promotion of changing legislation to oblige drivers to provide samples for toxicological testing, and the establishment of public information programs and specific actions aimed at young drivers to promote behavioral changes.     

An environment-friendly engine selection methodology for aerial vehicles

Emitted exhaust gases from aircraft are an issue of concern from an environmental perspective. Many research studies have been conducted aiming to reduce aircraft emissions in the hope of preventing any further increase in climate change and global warming. Within this scope, the present study intends to present a methodology for an optimum gas turbine engine selection with regard to emitted exhaust gases. The methodology focuses on five different turbofan engines which constitute the power unit of a commonly used passenger aircraft. At the end of the study, it is considered to be impossible to achieve a minimum exhaust emission for each gas. For this reason, it is considered to be better to optimize the engine with the aim of reducing nitrogen oxide emissions or other exhaust emissions.