A queen pheromone induces workers to kill sexual larvae in colonies of the red imported fire ant (<Emphasis Type="Italic">Solenopsis invicta</Emphasis>)

We conducted five bioassays to study how queens control the execution of sexual larvae by workers in colonies of the red imported fire ant, Solenopsis invicta. In each assay, subset colonies were made from many large polygyne colonies, and the 20 sexual larvae they contained were monitored over time. Sexual larvae mostly survived in queenless colonies, but were mostly killed in colonies with a single dealated queen, regardless of whether or not the queen was fertilized. The larvae were also killed when fresh corpses of queens were added to queenless colonies. Whereas acetone extracts of queens did not produce a significant increase in killings, extracts in buffered saline induced workers to execute most sexual larvae, indicating successful extraction of an execution pheromone. We identified the probable storage location of the chemical as the poison sac, and found both fresh (1 day) and old (21 day) extracts of poison sacs to be equally effective in inducing executions. The pheromone is stable at room temperature, perhaps because venom alkaloids also present in the extracts keep the pheromone from degrading. It is apparently either proteinaceous or associated with a proteinaceous molecule, a novel finding, as no queen pheromone of a proteinaceous nature has been previously demonstrated in ants.     

Gastric cancer: an epidemiological review

An attempt is made to synthesize the epidemiological literature and identify salient factors from the multitude of potential antecedents of gastric cancer, factors which to a greater or lesser degree create nonrandom variations in the distribution of the disease. Implicit in this approach is the notion that observation of spatial variations in the incidence of gastric cancer may lead to hypotheses relating to the biological, personal and physical environmental factors. An extensive bibliography accompanies the text.Formerly of the Department of Town Planning, University of Wales, College of Cardiff, PO Box 906, Cardiff CF1 3YN, Wales.     

Evolutionary social and biogeophysical changes in the Amazon,Ganges–Brahmaputra–Meghna and Mekong deltas

Policy-making in social-ecological systems increasingly looks to iterative, evolutionary approaches that can address the inherent complexity of interactions between human wellbeing, provision of goods, and the maintenance of ecosystem services. Here, we show how the analysis of available time-series in tropical delta regions over past decades can provide important insight into the social-ecological system dynamics in deltaic regions. The paper provides an exploratory analysis of the recent changes that have occurred in the major elements of three tropical deltaic social-ecological systems, such as demography, economy, health, climate, food, and water. Time-series data from official statistics, monitoring programmes, and Earth observation data are analysed to explore possible trends, slow and fast variables, and observed drivers of change in the Amazon, Ganges–Brahmaputra–Meghna and Mekong deltas. In the Ganges–Brahmaputra–Meghna delta zone, increasing gross domestic product and per capita income levels since the 1980s mirror rising levels of food and inland fish production. In contrast, non-food ecosystem services, such as water availability, water quality, and land stability appear to be deteriorating. In the Amazon delta, natural and anthropogenic perturbations are continuously degrading key ecosystem services, such as carbon storage in biomass and soils, the regulation of water balance, and the modulation of regional climate patterns. In the Mekong delta, rapid economic development, changing land-use practices, and salinity intrusion are progressively putting more pressure on the delivery of important provisioning services, such as rice and inland aquaculture production, which are key sources of staple food, farm incomes, and export revenue. Observed changes in many key indicators of ecosystem services point to a changing dynamic state and increased probability of systemic threshold transformations in the near future.     

Suppression of nucleation mode particles by biomass burning in an urban environment: a case study

Measurements of concentrations and size distributions of particles 4.7 to 160 nm were taken using an SMPS during the bonfire and firework celebrations on Bonfire Night in Leeds, UK, 2006. These celebrations provided an opportunity to study size distributions in a unique atmospheric pollution situation during and following a significant emission event due to open biomass burning. A log-normal fitting program was used to determine the characteristics of the modal groups present within hourly averaged size distributions. Results from the modal fitting showed that on bonfire night the smallest nucleation mode, which was present before and after the bonfire event and on comparison weekends, was not detected within the size distribution. In addition, there was a significant shift in the modal diameters of the remaining modes during the peak of the pollution event. Using the concept of a coagulation sink, the atmospheric lifetimes of smaller particles were significantly reduced during the pollution event, and thus were used to explain the disappearance of the smallest nucleation mode as well as changes in particle count mean diameters. The significance for particle mixing state is discussed.     

Combustion as the Principal Source of Carbonaceous Aerosol in the Ohio River Valley

Organic and elemental carbon and a number of carboxylic acids and n-alkanes were measured in aerosol samples collected at three sites in the Ohio River Valley between October 1980 and August 1981. Approximately 100 filters were analyzed for organic and elemental carbon for each site. For the 11-month period organic and elemental carbon comprised about 19 percent of the total aerosol mass with about two-thirds of the carbon as organic. Regression analysis showed that the principal source of organic carbon was combustion. The measurements of the specific organic compounds indicated a weak biogenic component to the organic aerosol.     

Impact of Indoor Environmental Parameters on Formaldehyde Concentrations in Unoccupied Research Houses

An environmental parameters study has examined the impact of indoor temperature (T) and relative humidity (RH) levels on formaldehyde (CH₂O) concentrations inside two unoccupied research houses where the primary CH₂O emitter is particleboard underlayment. The data were fit to a simple three-term, steady state model describing the T and RH dependence of CH₂O concentration in a single compartment with a single CH₂O emitter. The model incorporates an Arrhenius T dependence and a nonlinear RH dependence of the CH₂O vapor concentration within the solid CH₂O emitter. The RH dependence is based on Freundlich's theory of the adsorption of water vapor on solid surfaces. The model is used to estimate potential seasonal variation in CH₂O concentrations under specified experimental conditions inside the research houses. The modeled results indicate six- to ninefold variation between 18°C, 20% RH and 32°C, 80% RH, simulating potential winter/summer conditions with minimal indoor climate control. In comparison, Indoor conditions ranging from 20°C, 30% RH to 26°C, 60% RH yielded approximate two- to fourfold fluctuations in CH₂O concentration.

The research house data were also used to evaluate the limitations and applicability of more complex five-term models developed from small-scale chamber studies of the environmental dependence of CH₂O emissions from particleboard underlayment. These models also incorporate a linear T and RH dependence of the CH₂O transport rate through the CH₂O emitter in addition to the T and RH dependence of the CH₂O concentration within the emitter. Good correlation is observed between the results of the research house studies and 1) a selected (i.e., single) underlayment model over a broad range of environmental conditions and 2) a combined underlayment model over a restricted range of environmental conditions.     

Four priorities for new links between conservation science and accounting research

Article impact statement: New collaborations with accounting research can improve conservation impact of ecosystem-based information systems.     

Practical actions for applied systematic conservation planning

Systematic conservation planning is intended to inform spatially explicit decision making. Doing so requires that it be integrated into complex regulatory and governance processes, and there are limited instances where this has been achieved effectively. South Africa is a global leader in the application of conservation plans, the outputs of which are widely used for spatial planning and decision making in many spheres of government. We aimed to determine how conservation planning in the country progressed from theory to implementation, and to identify practical actions that enabled this transition, by assessing temporal trends in the characteristics of conservation plans (1990–2017, n = 94). Since 2010 conservation planning has entered an operational period characterized by government leadership of plans, administrative rather than ecological planning domains, decreasing size of planning units, increasing emphasis on end-user products, and scheduled revision of plans. Key actions that enabled this progression include transitioning leadership of plans from scientists to practitioners, building capacity within implementing agencies, creating opportunities to integrate plans in legislative processes, establishing a strong community of practice, adopting implementation-focused methods, and balancing standardization with innovation. Learning from this model will allow other countries, particularly those with a similar megadiverse, developing context, to operationalize conservation planning into spatial planning and decision making.     

Toxic effects of oral 2-amino-4,6-dinitrotoluene in the Western fence lizard (Sceloporus occidentalis)

The compound 2-amino-4,6-dinitrotoluene (2A-DNT) was evaluated under laboratory conditions in the Western fence lizard (Sceloporus occidentalis) to assess the potential for reptile toxicity. Oral LD₅₀ values were 1406 and 1867 mg/kg for male and female lizards, respectively. Based on responses from a 14-day subacute study, a 60-day subchronic experiment followed where lizards were orally dosed at 0, 5, 15, 20, 25, 30 mg/kg-d. At day 60, number of days and survivors, food consumption, and change in body weight were inversely related to dose. Signs of toxicity were characterized by anorexia and generalized cachexia. Significant adverse histopathology was observed in hepatic tissue at ≥15 mg/kg-d, consistent with hepatocellular transdifferentiation. Based on survival, loss of body weight, diminished food intake, changes in liver, kidney, and testes, and increased blood urea nitrogen, these data suggest a LOAEL of 15 mg/kg-d and a NOAEL of 5 mg/kg-d in S. occidentalis.     

Predation risk makes bees reject rewarding flowers and reduce foraging activity

In the absence of predators, pollinators can often maximize their foraging success by visiting the most rewarding flowers. However, if predators use those highly rewarding flowers to locate their prey, pollinators may benefit from changing their foraging preferences to accept less rewarding flowers. Previous studies have shown that some predators, such as crab spiders, indeed hunt preferentially on the most pollinator-attractive flowers. In order to determine whether predation risk can alter pollinator preferences, we conducted laboratory experiments on the foraging behavior of bumble bees (Bombus impatiens) when predation risk was associated with a particular reward level (measured here as sugar concentration). Bees foraged in arenas containing a choice of a high-reward and a low-reward artificial flower. On a bee’s first foraging trip, it was either lightly squeezed with forceps, to simulate a crab spider attack, or was allowed to forage safely. The foragers’ subsequent visits were recorded for between 1 and 4 h without any further simulated attacks. Compared to bees that foraged safely, bees that experienced a simulated attack on a low-reward artificial flower had reduced foraging activity. However, bees attacked on a high-reward artificial flower were more likely to visit low-reward artificial flowers on subsequent foraging trips. Forager body size, which is thought to affect vulnerability to capture by predators, did not have an effect on response to an attack. Predation risk can thus alter pollinator foraging behavior in ways that influence the number and reward level of flowers that are visited.