Predator foraging behavior in response to perception and learning by its prey: interactions between orb-spinning spiders and stingless bees

Although rewarded bees learn and remember colors and patterns, they have difficulty in learning to avoid negative stimuli such as decorated spider webs spun by Argiope argentata. A. argentata decorates its web with silk patterns that vary unpredictably (Fig. 1) and thus foraging insects that return to sites where spiders are found encounter new visual cues daily. Stingless bees can learn to avoid spider webs but avoidance-learning is slowed or inhibited by daily variation in web decorations (Figs. 3,4; Tables 1,2). In addition, even if bees learn to avoid decorated webs found in one location, they are unable to generalize learned-avoidance responses to similarly decorated webs found at other sites. A. argentata seems to have evolved a foraging behavior that is tied to the ways insects perceive and process information about their environment. Because of the evolutionary importance of bee-flower interdependence, the predatory behavior of web-decorating spiders may be difficult for natural selection to act against.     

Defensive behavior of ants in a mutualistic relationship with aphids

Mutualistic relationships between ants and aphids are well studied but it is unknown if aphid-attending ants place a greater relative importance on defending aphids from aphid-predators or from competing ant colonies. We tested the hypothesis that aphid-attending ants defend their aphids against aphid-predators more aggressively than against ants from neighboring colonies. We conducted introduction trials by placing an individual non-predatory insect, an aphid-predator, or a foreign conspecific ant on the leaf of a resident ant. We found that ants did not attack non-predatory insects, but did attack competing ants and aphid-predators. When we presented resident ants with both the threats (i.e., predator and competitor) at the same time, residents always attacked potential competitors as opposed to aphid-predators. We suggest this behavior may reduce the likelihood of raids by neighboring colonies. Ants appear to balance both the energetic costs of making an attack and the costs associated with losing aphids to a predator, against the benefits of signaling their defensive ability to rivals and/or preventing rivals from gaining knowledge of a potential food resource.     

Social thermoregulation exerts more influence than microclimate on forest roost preferences by a cavity-dwelling bat

Nest or roost temperature (T _roost) is thought to impact reproductive fitness in many endotherms but few studies have directly tested the hypothesis that naturally occurring variability in nest or roost microclimate is large enough to affect reproductive success. We conducted a field experiment to test whether roost selection by cavity-dwelling, reproductive female big brown bats (Eptesicus fuscus) is more strongly influenced by roost microclimate or a physical characteristic of roosts that facilitates social thermoregulation (i.e., cavity volume). We quantified spatial variability in T _roost within different-sized, unoccupied cavities and also recorded T _roost in occupied vs unoccupied roost trees. We used equations relating energy use and ambient temperature for big brown bats to calculate values of daily energy expenditure from T _roost data because energy is a currency that likely affects reproductive fitness. We found no difference between maximum and minimum T _roost, spatial variability in T _roost, or predicted energy expenditure in more-preferred vs less-preferred roosts. However, there was a significant difference between T _roost and predicted energy expenditure when we compared occupied vs unoccupied roosts. The presence of bats increased T _roost by as much as 7°C, and there was a significant positive correlation between the number of bats occupying a roost, maximum daily T _roost, and energy savings. We calculate that, on average, a normothermic individual would save about 6.5 kJ/day (roughly 9% of the daily energy budget) by roosting in an occupied cavity relative to roosting alone and that savings may increase to 40 kJ/day (about 53% of the energy budget) for an individual roosting in a group of 45 bats. Our findings suggest that variability in microclimate among potential roost or nest sites may be less important to some cavity-dwelling endotherms than has been suggested in previous studies. Our results reinforce the importance of sociality and social thermoregulation to the roosting ecology of forest-living bats and socially roosting or nesting endotherms in general.     

Investigating freshwater periphyton community response to uranium with phospholipid fatty acid and denaturing gradient gel electrophoresis analyses

Periphyton communities can be used as monitors of ecosystem health and as indicators of contamination in lotic systems. Measures of biomass, community structure, and genetic diversity were used to investigate impacts of uranium (U) exposure on periphyton. Laboratory exposures of periphyton in river water amended with 238U were performed for 5 days, followed by 2 days of U depuration in unamended river water. Productivity as measured by biomass was not affected by concentrations up to 100 microg238U L(-1). Phospholipid fatty acid (PLFA) profiles and denaturing gradient gel electrophoresis (DGGE) banding patterns revealed no changes in community or genetic structure related to U exposure. We suggest that the periphyton community as a whole was not significantly impacted by exposures of 238U up to a concentration of 100 microgL(-1). These findings have significance for the assessment and prediction of U impacts on aquatic ecosystems.     

The psychological impact of traffic injuries sustained in a road crash by bicyclists: A prospective study

Objective: The objective of this study was to investigate the psychological impact of traffic injuries in bicyclists (cyclists) in comparison to car occupants who also sustained traffic injuries. Factors predictive of elevated psychological distress were also investigated.

Methods: An inception cohort prospective design was used. Participants included cyclists aged ≥17 years (mean age 41.7 years) who sustained a physical injury (n = 238) assessed within 28 days of the crash, following medical examination by a registered health care practitioner. Injury included musculoskeletal and soft tissue injuries and minor/moderate traumatic brain injury (TBI), excluding severe TBI, spinal cord injury, and severe multiple fractures. Assessment also occurred 6 months postinjury. Telephone-administered interviews assessed a suite of measures including sociodemographic, preinjury health and injury factors. Psychological impact was measured by pain catastrophization, trauma-related distress, and general psychological distress. The psychological health of the cyclists was compared to that of the car occupants (n = 234; mean age 43.1 years). A mixed model repeated measures analysis, adjusted for confounding factors, was used to determine differences between groups and regression analyses were used to determine contributors to psychological health in the cyclists 6 months postinjury.

Results: Cyclists had significantly better psychological health (e.g., lower pain catastrophizing, lower rates of probable posttraumatic stress disorder [PTSD], and lower general distress levels) compared to car occupants at baseline and 6 months postinjury. Factors predictive of cyclists' psychological distress included younger age, greater perceived danger of death, poorer preinjury health, and greater amount of time in hospital after the injury.

Conclusions: These data provide insight into how cyclists perceive and adjust to their traffic injuries compared to drivers and passengers who sustain traffic injuries, as well as direction for preventing the development of severe psychological injury. Future research should examine the utility of predictors of psychological health to improve recovery.     

Are communal pukeko caught in the prisoner's dilemma?

Summary The prisoner's dilemma of game theory provides a possible explanation for communal breeding in the pukeko (Porphyrio porphyrio, Aves) where group breeding birds are at a reproductive disavantag compared to pairs. Territorial defence is largely the realm of males. A male who defect on neighbours by taking in an extra male defender and so becoming communal stands to gain territorial area and possibly higher reproductive success. Neighbours are forced to follow suit if additional males are available or lose their territory and therefore their breeding opportunities. If neighbours also admit an extra defender, the initial defector loses his advantages and all males end up with the lower breeding success of communal groups. Such defection to a communal habit appears to be the only stable solution.     

The effect of wastewater treatment on antibiotic resistance in Escherichia coli and Enterococcus sp.

The effects of wastewater treatment on the proportion of Escherichia coli and Enterococcus sp. resistant to specific antibiotics were investigated at two facilities in Davis County, Utah, one of which received hospital waste. Samples were taken from the influent, effluent before disinfection, and secondary anaerobic sludge digester effluent. There was very little difference in antibiotic resistance among E. coli in the inflow waters of the plants but the plant receiving hospital waste had a significantly higher proportion of antibiotic resistant Enterococcus. The effect of wastewater treatment on antibiotic resistance was more pronounced on enterococci than E. coli. Although some increases in antibiotic resistance were observed, the general trend seemed to be a decrease in resistance, especially in the proportion of multidrug resistant Enterococcus sp.     

Fate, effects and potential environmental risks of ethylene glycol: a review

The fate, effects, and potential environmental risks of ethylene glycol (EG) in the environment were examined. EG undergoes rapid biodegradation in aerobic and anaerobic environments (approximately 100% removal of EG within 24 h to 28 days). In air, EG reacts with photo-chemically produced hydroxyl radicals with a resulting atmospheric half-life of 2 days. Acute toxicity values (LC(50)s and EC(50)s) were generally >10,000 mg/l for fish and aquatic invertebrates. The data collectively show that EG is not persistent in air, surface water, soil, or groundwater, is practically non-toxic to aquatic organisms, and does not bioaccumulate in aquatic organisms. Potential long-term, quasi-steady state regional concentrations of EG estimated with a multi-media model for air, water, soil, and sediment were all less than predicted no effect concentrations (PNECs).