Exposure to endocrine disrupting chemicals (EDCs), compounds that disrupt the normal hormone signaling pathways, can lead to a wide variety of negative outcomes in organisms. Although it has been shown that endocrine signaling systems interact with each other, research into the effects of EDCs has typically focused on a single endocrine axis independent of all others. This means that alterations in processes associated with nontargeted endocrine systems may be ignored. The interaction may also make it difficult to identify mechanisms of newly discovered EDCs. Because of these potential issues, it is important to understand the outcomes of endocrine axis interaction in organisms used as models for EDC testing. This experiment examined the effects of exposure to model thyroid disruptors, thyroxine (T4) and propylthiouracil (PTU), on reproductive function in the fathead minnow (Pimephales promelas). This species is a commonly used model organism but the outcomes of thyroid-reproductive system interaction are unknown. In addition to endpoints traditionally associated with the thyroid (e.g., thyroid related gene expression), this study included endpoints associated with overall reproductive function (e.g., number of eggs laid) and those more specific to the reproductive endocrine system (e.g., sex steroid related gene expression). It was found that model thyroid disruption lead to alterations in several thyroid and reproductive endpoints. Information on how thyroid disruption affects reproductive function in the fathead minnow will aid future experiments on EDC exposure in this species.

Carnivorous plants inhabit nutrient-poor environments, and they supplement nutrient uptake by capturing and absorbing nutrients from prey, such as insects. Like other plants, carnivorous plants are subject to loss of nutrient-containing tissues to herbivores. Because they occur in low-nutrient environments, tissue loss to herbivory can be expected to have a particularly strong negative effect on carnivorous plants. However, herbivory in carnivorous plants has not been well studied. In this study, we quantified tissue and nutrient losses sustained from herbivory by larvae of the specialist moth, Exyra semicrocea, in a population of pitcher plants, Sarracenia alata. We conducted field surveys, analyses of areal foliar damage, nutrient analyses, and feeding trials. In the study population, 83% (0.83 ± 0.033; mean ± SE) of pitchers were damaged by E. semicrocea. On average, approximately 15% of each affected pitcher was consumed before the larvae began feeding on another pitcher. Mean foliar nitrogen concentration was 1.19%, resulting in a mean nitrogen loss to consumption of 0.24 ± 0.041 mg per pitcher (N = 40). Mean foliar phosphorus concentration was 0.044%, resulting in a mean phosphorus loss per pitcher of 0.0086 ± 0.0015 mg (N = 37). In preliminary feeding trials, 4th and 5th instar larvae consumed 32 ± 3.8 mg /day and 33 ± 4.3 mg /day, respectively. Based on these consumption rates, estimated mean time spent feeding on a single pitcher was 2.5 ± 0.18 days (N = 95). Current studies are evaluating the impact of herbivory on reproductive output of these plants.

Mercury (Hg) is a toxic heavy metal that contaminates aquatic food webs. Methylated Hg can accumulate in fish, posing health hazards to fish-eating birds. All water bodies in the south central U.S. are contaminated with Hg but the level of contamination varies with ecoregion. Spatial patterns in the risk that Hg-contaminated fish pose to fish-eating birds is not understood. The objective of this study was to quantify Hg levels in a common fish species (bluegill, Lepomis macrochirus) and determine if the Hg contamination of bluegill poses a risk to a native fish-eating bird (the double-crested cormorant, Phalacrocorax auritus) in 14 USEPA level III ecoregions in six states in the south central U.S. We used the National Descriptive Model for Mercury in Fish to estimate the concentration of Hg in 8-cm total length bluegill in 835 sites. We then compared those Hg concentrations to the cormorant wildlife value (WV), an estimate of the minimum concentration of Hg in the diet of the consumer to cause physiologically significant doses. The concentration of Hg in bluegill exceeded the WV in 38% of sampling sites across the region. Within the 14 ecoregions the proportion of sampling sites that exceeded the wildlife value ranged from 7% to 77%. Ecoregions with highest Hg deposition from the atmosphere adjusted for conifer coverage had the highest proportion of sampling sites exceeding the WV.

The United States requires that whole effluent and chemicals be tested for aquatic toxicity using the fathead minnow larval growth and survival (LGS) test. While the LGS test has been effective for determining acute and chronic aquatic toxicity, a fathead minnow fish embryo toxicity (FET) test has been proposed as a refinement to the LGS as younger organisms are thought to experience less stress during toxicant exposure. Presently, the FET test protocol does not include endpoints that allow for the prediction of non-lethal adverse outcomes or chronic toxicity. This limits its utility relative to other test types. This study investigated the utility of sublethal endpoints related to cardiovascular function and development (e.g., heart rate, pericardial area, and cardiovascular related genes) as additional FET test metrics. FET tests were run with four model toxicants: 3,4 –dichloroaniline, sodium chloride, cadmium, and triclosan. Heart rate was evaluated at 76 hpf, while pericardial area was assessed at 120 hpf. Hatched larvae were sampled at the conclusion of the tests (120hpf) for gene expression analysis. Pericardial area was identified as the most sensitive sub-lethal endpoint, although alterations were also seen in the other metrics investigated. These alterations suggest that sublethal endpoints related to cardiovascular function and morphology may be useful for estimating non-lethal adverse effects and chronic toxicity. Future studies aimed at linking alterations in these endpoints to longer term adverse impacts are needed to fully describe the predictive power of these metrics in whole effluent and chemical toxicity testing.

Wind energy is a renewable resource with many environmental benefits. However, one environmental impact from wind energy is on bats, because bats can be killed when they fly into the path of spinning turbine blades. Estimates of bat fatalities at wind facilities across the U.S. exceed 500,000 per year. One potential way to reduce bat fatalities at wind facilities is with acoustic deterrents. These devices, including the newly designed acoustic deterrent tested during this study, produce sound which is intended to disrupt bat echolocation. We used video cameras to evaluate bat activity and behavioral responses to the acoustic deterrent at a wind facility in north-central Texas. The acoustic deterrent reduced the level of bat activity by up to 90%, and also altered the flight behavior of bats. Our data indicate that this acoustic deterrent could significantly reduce bat fatalities at wind facilities once the devices are installed on turbines.