Tooth hardness increases with zinc-content in mandibles of young adult leaf-cutter ants

A wide variety of arthropods and members of other phyla have elevated concentrations of Zn, Mn, other heavy metals and halogens in their jaws, leg claws, and other "tools" for interacting with the environment. While measured Zn concentrations reach 25% of dry mass in scorpion stings, concentrations are often lower than this and the enriched structures are not heavily biomineralized like vertebrate teeth and the radula of mollusks. For this reason, the degree to which the inorganic components of these structures modify their mechanical properties is in question. Here we address this problem by measuring hardness during the development of Zn accumulations in ant mandibles. We found that Zn is incorporated into the mandibular teeth of leaf-cutter ants during early adult life, reaching concentrations of about 16% of dry mass. We show that the hardness of the mandibular teeth increases nearly three-fold as the adults age and that hardness correlates with Zn content (r=0.91). We suggest that young adults rarely cut leaves partly because their mandibles are not yet rich in Zn. Zinc enrichment (along with enrichment by other heavy metals and halogens) may play an unrecognized role in the behavioral ecology and evolution of a wide variety of invertebrates.     

Alphafetoprotein,cholinesterases and rapidly adhering cells in the prenatal diagnosis of neural tube defects

Amniotic fluid cholinesterases tested on polyacrylamide gel and rapidly adhering cell analysis were compared in their efficiency at diagnosing fetal neural tube defects in three cases where the alphafetoprotein results were equivocal. While rapidly adhering cells were also equivocal, the cholinesterases consistently gave a clear indication of fetal abnormality.     

Heavy metals and selenium in feathers of three shorebird species from Delaware bay

Concentrations of lead, cadmium, mercury, selenium, chromium and manganese were examined in breast feathers of shorebirds migrating north through Cape May, New Jersey in 1991 and 1992. Although we predicted that metal levels would be positively correlated with weight, this was only true for mercury in red knots (Calidris canutus). Selenium was negatively correlated with weight in red knots. No other significant correlation of metal concentrations with weight were found. Lead and mercury were highest in sanderlings (C. alba). Selenium and manganese were highest in red knots, while chromium and cadmium levels were highest in semipalmated sandpipers (C. pusilus). For 1991, interspecific metals differences were significant for all metals except lead. For semipalmated sandpipers, cadmium and chromium concentrations were significantly higher in 1991 while managese concentrations were significantly higher in 1992.     

Assessing the Relative Severity of Stressors at a Watershed Scale

Water quality monitoring data are usually used independently to report on the condition of streams and watersheds. For example, watersheds are often rated as good, fair, or poor with regard to a single stressor or with regard to an index of biotic integrity. The utility of monitoring data may be enhanced by integrating stressor-response information with the observed stressor data, and reporting stressor levels in terms of their relative effects upon valued ecological resources. We estimated stressor-response relationships at the regional scale using data collected in the Eastern Cornbelt Plains Ecoregion of Ohio. Generalized additive models were used to visualize stressor-response relationships. Piecewise linear functions and simple linear functions were then used to parameterize the observed responses. Parameters derived from the regional models were used to scale observations of stressors in the Big Darby Creek watershed, OH. After scaling, stressors were compared in terms of their spatial distribution and in terms of the severity with which they influenced the biological endpoint of interest. Stressors most strongly associated with the current ecological condition of the watershed were identified. In the Big Darby Creek watershed, decreases in substrate quality were associated with the most severe decrements in biological condition. At smaller decrements in biological condition, three stressors were important: substrate quality, riparian quality, and increased concentrations of NOx.     

Sobriety checkpoint and open container laws in the United States: Associations with reported drinking-driving

Objective: The objective of this study was to assess how 2 types of drinking-driving laws—permitting sobriety checkpoints and prohibiting open containers of alcohol in motor vehicles—are associated with drinking-driving and how enforcement efforts may affect these associations.

Methods: We obtained 2010 data on state-level drinking-driving laws and individual-level self-reported drinking-driving from archival sources (Alcohol Policy Information System, NHTSA, and Behavioral Risk Factor Surveillance System). We measured enforcement of the laws via a 2009 survey of state patrol agencies. We computed multilevel regression models (separate models for each type of law) that first examined how having the state law predicted drinking-driving, controlling for various state- and individual-level covariates; we then added the corresponding enforcement measure as another potential predictor.

Results: We found that states with a sobriety checkpoint law, compared with those without a law, had 18.2% lower drinking-driving; states that conducted sobriety checks at least monthly (vs. not conducting checks) had 40.6% lower drinking-driving (the state law variable was not significant when enforcement was added). We found no significant association between having an open container law and drinking-driving, but states that conducted open container enforcement, regardless of having a law, had 17.6% less drinking-driving.

Conclusion: Our results suggest that having a sobriety checkpoint law and conducting checkpoints as well as enforcement of open containers laws may be effective strategies for addressing drinking-driving.     

Stable Isotope Probing to Confirm Field‐Scale Co‐Metabolic Biodegradation of 1,4‐Dioxane

1,4‐Dioxane, a common co‐contaminant with chlorinated solvents, is present in groundwater at Site 24 at Vandenberg Air Force Base in California. Historical use of chlorinated solvents resulted in concentrations of 1,4‐dioxane in groundwater up to approximately 2,000 μg/L. Starting in 2013, an in situ propane biosparge system operation demonstrated reductions in 1,4‐dioxane concentrations in groundwater. The work detailed herein extends the efforts of the first field demonstration to a second phase and confirms the biodegradation mechanism via use of stable isotope probing (SIP). After two months of operation, 1,4‐dioxane concentrations decreased approximately 45 to 83 percent at monitoring locations in the test area. The results of the SIP confirmed ¹³C‐enriched 1,4‐dioxane was transformed into dissolved inorganic carbon (suggesting mineralization to carbon dioxide) and incorporated into microbial biomass (likely attributed to metabolic uptake of biotransformation intermediates or of carbon dioxide).  ©2016 Wiley Periodicals, Inc.     

Understanding Human–Landscape Interactions in the “Anthropocene”

This article summarizes the primary outcomes of an interdisciplinary workshop in 2010, sponsored by the U.S. National Science Foundation, focused on developing key questions and integrative themes for advancing the science of human–landscape systems. The workshop was a response to a grand challenge identified recently by the U.S. National Research Council (2010a)—“How will Earth’s surface evolve in the “Anthropocene?”—suggesting that new theories and methodological approaches are needed to tackle increasingly complex human–landscape interactions in the new era. A new science of human–landscape systems recognizes the interdependence of hydro-geomorphological, ecological, and human processes and functions. Advances within a range of disciplines spanning the physical, biological, and social sciences are therefore needed to contribute toward interdisciplinary research that lies at the heart of the science. Four integrative research themes were identified—thresholds/tipping points, time scales and time lags, spatial scales and boundaries, and feedback loops—serving as potential focal points around which theory can be built for human–landscape systems. Implementing the integrative themes requires that the research communities: (1) establish common metrics to describe and quantify human, biological, and geomorphological systems; (2) develop new ways to integrate diverse data and methods; and (3) focus on synthesis, generalization, and meta-analyses, as individual case studies continue to accumulate. Challenges to meeting these needs center on effective communication and collaboration across diverse disciplines spanning the natural and social scientific divide. Creating venues and mechanisms for sustained focused interdisciplinary collaborations, such as synthesis centers, becomes extraordinarily important for advancing the science.