There has been mounting concern from both scientists and the public regarding the presence and biological effects of emerging contaminants (ECs) in the environment. ECs can be defined as contaminants that are not currently subject to routine monitoring programs or regulatory standards, but that have the potential to cause adverse environmental or human health effects. These pollutants are being found in increasing levels in aquatic environments, and as such, the possible health impacts of these contaminants have become a growing focus of scientific research. Some classes of ECs, especially those that disrupt neurological development or thyroid hormone levels, have the potential to alter the growth, development, and function of the eyes. For many organisms, eyesight is crucial to survival as it allows them to avoid danger, obtain food, and perform many other important activities. However, reliable methods for testing the effects of ECs on vision are scarce, so the full impact of many ECs remains unknown. As such, this project aimed to determine dependable ways to measure visual development and function in the fathead minnow, a small fish frequently used to screen for chemical toxicity and adverse effects. We found that the feeding assay was a straightforward and promising option for measuring vision because it estimated the average prey capture ability of a group in a relatively short amount of time. We also found that the optomotor assay, while compelling, presented no significant differences between groups for the variables tested. However, there were practical differences observed throughout the trials, indicating that although the assay is complex, further testing and development could transform it into a reliable source of data.

Zebra and Quagga mussels are aquatic and highly invasive freshwater bivalve molluscs native to Eurasia. They have spread at an exponential rate into bodies of water throughout the country by means of our interconnected waterway. Prior analysis of their distribution has determined a consistent global pattern in which a population of zebra mussels initially invades a body of water and subsequently, a population of quagga mussels is established in the same region. Despite differential habitat preferences, both species have been found to live and reproduce in the same location. Since both species exhibit broadcast spawning as a reproductive mechanism, the potential for hybridization exists; this potential was analyzed via evaluating the initial fertilization and early embryonic cleavage stages required for production of viable hybrid offspring. A series of hybridization crosses were performed and compared against a control. Fertilization events observed and analyzed included motility and chemotaxis, the acrosome reaction, sperm binding and entry into the egg cytoplasm, and finally cleavage and early development. Inability to produce viable offspring suggests a hybridization-block has been established between the two species at the level of fertilization or early development.

Some classes of endocrine disrupting compounds in the environment have the ability to alter thyroid function. Such thyroid disrupting compounds are known to influence growth and development, but recent studies suggest that thyroid disruption can also have adverse effects on reproduction. A recent study in the Jeffries lab demonstrated that early-life stage thyroid disruption caused decreased reproductive output in fathead minnows (Pimephales promelas), even after a prolonged period of depuration. However, the mechanisms connecting early life stage thyroid disruption to altered reproduction during adulthood remain elusive. This study sought to determine whether alterations in reproductive success following thyroid disruption were a result of male or female reproductive performance in an effort to narrow potential mechanisms by which thyroid disrupting compounds alter reproduction. The results of this study bring insight to the underlying cause of decreased reproductive output following thyroid inhibition.

Carnivorous plants occupy nutrient-poor soils and have evolved traits that allow them to obtain nutrients by capturing and digesting insects. The pale pitcher plant, Sarracenia alata, uses passive pitfall traps to capture their insect prey. Although studies have examined prey composition for S. alata, it is unknown whether this species is selective in prey capture or whether it captures insects in proportion to their abundance in the environment. The purpose of this study was to compare prey capture of S. alata pitchers with the available insects to determine whether this species is selective in prey capture. The available insects were sampled using artificial sticky traps in the vicinity of the pitchers. The insects in the study were identified first to the taxonomic level of order and then further identified to "morphospecies" as a means of examining preference on a finer scale. The relative proportions of insects in specific orders differed between artificial traps and plants. Although dipterans were a major component of capture in both artificial traps and plants, the relative proportions of morphospecies differed between the two. These results support the hypothesis that S. alata is selective in its prey capture, but further studies are needed that use different methods of measuring the available insects in order to avoid potential bias.

Our team will answer the question how Penicillium mold grows in a microgravity environment versus Earth’s gravity. This question answers or sparks several other questions such as is it a viable solution for some antibiotics in space or how do antibiotics like penicillin work in the body in space. Will it grow more or will it be the same or maybe grow less? The purpose of our experiment is to provide a viable solution to some bacterial infections in space. Bacteria in space tends to act more violently so maybe good bacteria or mold will act more furiously to kill those bacteria. Our hypothesis is that it will grow better. This is based off of the fact that in an earlier SSEP experiment the polymers absorbed more water. Which might be the same for organisms like mold so it would make it easier to absorb water. Plus with lower gravity organisms tend to grow larger at least that is many scientist hypotheses. So since there is practically no major gravity or forces in space may be the mold will grow larger than usual. Our group believes this based on the fact that we have researched.

Our experiment is about diabetes and Humalog synthetic insulin crystallization in a microgravity environment. We feel like this is a good experiment to design because we could find out if there is a way to prevent crystallization of insulin, especially if we understand how it happens in microgravity. When insulin crystallizes, the bacteria that usually makes it viable stops working. This would cause it to be ineffective for patients in dire need of this medication. To complete this experiment we are going to keep the insulin in a type 1 FME at the International space station (ISS) at above 65℉ to see if it crystallizes within a certain amount time. We will keep the experiment refrigerated at or below 40℉ during transportation to the ISS and again on arrival back to Earth’s gravity. Refrigeration slows the crystallization growth and this is how it is stored on Earth. Keeping our experiment refrigerated during transportation is an important step because the insulin crystallization growth should only be measured while in microgravity. We will be conducting the same experiment, using the same time frame and refrigeration needs before and after, for our earth bound experiment.

Our experiment is how well will a hornwort plant purify polluted water in microgravity. We will see how it will purify at the same rate as it does in full gravity. We chose this plant because they can purify water and they grow at a fast rate. This will help astronauts because if they run out of water they can grow hornwort even if the only water they have is polluted. Also, it will help them to have purified water if their water system breaks down. The hornwort plant will be growing on the way from Earth to the ISS. The experiment will be purifying the polluted water in microgravity for 5-6 days. Then the formalin will be added to the plant to stop its growth and preserve the sample. We are polluting the water with Cyanobacteria, which is more commonly known as blue green algae. We will know it has worked if the polluted water has become purified after it has been tested.

Previous studies, including those in the Jeffries lab, have shown that female animals are able to fight and survive infection better than males. However, the underlying cause of this difference remains unclear. Because many differences between males and females are due to differences in sex steroid hormone (e.g., estrogen, testosterone, etc.) concentrations, it is possible that differences in immune function are also due to such differences in hormone levels. The objective of this study is to uncover the role of sex steroid hormones in the immune response of fathead minnows (Pimephales promelas). Because females exhibit better pathogen resistance than males, it is hypothesized that estrogen (a “female” hormone) enhances immune system function. The results of this study provides insight into the potential crosstalk between the reproductive and immune systems, as well as a better understanding of the role of sex hormones in the organism.

The fathead minnow (Pimephales promelas), a small fish model often used to screen for reproductive endocrine disrupting compounds, has recently been used by some investigators to screen for chemicals with thyroid disrupting capabilities. However, it is uncertain how known thyroid disruptors affect various markers of thyroid disruption in this species. This study aimed to fill this gap in knowledge by assessing the sensitivity of endpoints known to be responsive to thyroid disruption in other closely-related species in larval fathead minnows. In addition, we sought to uncover how the timing and length of exposure influenced the response of these endpoints. To accomplish these objectives, larval fathead minnows were exposed to various doses of propylthiouracil (PTU; a known thyroid disruptor) and thyroxine (T4; a known thyroid stimulant) for 35 days. Several metrics indicative of alterations in thyroid hormone status (e.g., thyroid related gene expression, growth, thyroid cell follicular height, etc.) were measured on day 7, 21, and 35. The results of this study provide valuable information that can be utilized in developing fathead minnow thyroid disrupting chemical screening assays.

Habitat maps derived from remotely sensed data are strong predictors of wildlife distributions, outperforming traditional on the ground vegetation structure surveys. Texas Parks and Wildlife created a statewide habitat map in 2014 featuring 398 vegetation classes to 10-meter resolution. The Great Trinity Forest is the largest urban forest in the United States, with 3,000 continuous hectares within the city of Dallas. As part of our wider study of the forest’s wildlife, we edited Texas Parks and Wildlife’s habitat to more accurately and meaningfully reflect habitat distinctions in the Great Trinity Forest. First we adjusted the locations and boundaries of waterways to reflect changes in their location over the past four years. Then we reclassified the bottomland hardwood forest habitat type (BHF) to reflect different succession stages of forest growth. Using LIDAR and aerial images we calculated canopy heights and reclassified BHF using those heights as primary BHF, secondary BHF, or early successional bottomlands.

Methylmercury (MeHg) is an environmental contaminant that can have adverse effects on wildlife. Because inorganic Hg is converted to MeHg primarily in aquatic ecosystems, studies of MeHg contamination of food webs have historically focused on aquatic organisms. However, recent studies have found that emergent aquatic insects (e.g. mayflies and dragonflies) can transport MeHg to terrestrial predators like songbirds, and this could have implications for species in decline such as Red-winged blackbirds (Agelaius phoeniceus). Red-winged blackbirds are odonate (dragonflies and damselflies) predators, and odonates can make up 50 – 90% of a Red-winged blackbird’s diet during the breeding season. Red-winged blackbirds have declined throughout their range by 30% over the last 50 years. Their decline is due in part to loss of wetland habitat, but the consumption of MeHg contaminated prey items could also be having an effect. Several studies have reported MeHg contamination of Red-winged blackbirds, and yet, the potential effect of diet on MeHg contamination in Red-winged blackbirds has not been studied. I collected data on blood MeHg level of Red-winged blackbird nestlings and the emergence rate of odonates during the summer of 2017 at the Eagle Mountain Hatchery Experimental Pond Facility in Tarrant County, Texas. I used the ArcGIS Space Time Cube to identify spatiotemporal hot spots of nestling MeHg level and odonate emergence, and I used linear regression models to see how well proximity to odonate emergence hotspots predicted nestling MeHg hotspots.

Cancer is the second leading cause of death and will directly affect approximately 40% of the people in the United States over the course of their life. Chemotherapy has been shown to be an effective therapeutic strategy, but it lacks specificity, resulting in a multitude of negative side effects. Targeted therapies such as Herceptin, Iressa, and Nivolumab have shown increased effectiveness against cancer by attacking specific molecules in the target cell. For example, Herceptin inhibits the HER2 protein, which is overproduced in some breast cancer cells, and stops cell division. Biotin is an innate coenzyme for carbohydrate, lipid and protein metabolism. Certain cancer types overexpress biotin transporters on the surface of each cancer cell in order to increase biotin absorption necessary for metabolic processes. Furthermore, the intracellular environment in cancer cells is more reducing compared to non-cancer cells due to increased metabolism. Ferrocene is an iron-based organometallic molecule that has been shown to generate reactive oxygen species (ROS) in the reducing environment of cancer cells. Given that certain cancer cells absorb biotin with a higher efficiency, we hypothesize that linking biotin to ferrocene will increase the efficiency of ferrocene entering the cell and result in selective cancer cell death. Therefore, we have produced a library of biotin-ferrocene conjugates to selectively target cancer cell lines that over express biotin receptor sites. Experiments were conducted utilizing ferrocene and a variety of ferrocene-biotin conjugates (C1, C2, 2) in both cancer (MCF-7) and noncancer (HEK 293) cell lines in order to compare the relative toxicity between compounds.

Many rainbow trout (Oncorhynchus mykiss) populations exhibit partial migration, where resident and migrant individuals coexist in a single population. Due to anthropogenic, environmental, and population-specific factors, migratory individuals have been decreasing in frequency across the continental United States. Biologically, whether an individual will migrate is determined by both genetic and environmental factors. Although migration in many salmonids is known to be highly heritable, the environment plays an overriding role. Previous studies investigating the genetic basis of migration have failed to control for environmental variance and, consequently, the genes and regions of the genome underlying the development of the migratory phenotype remain unknown. We used data from a common garden experiment to identify single nucleotide polymorphisms (SNPs) significantly associated with migration in the F1 generation of a resident-by-resident and a migrant-by-migrant cross. We genotyped 192 F1 individuals on an Affymetrix SNP chip at 57,501 known polymorphic locations throughout the genome. We identified 5002 significant SNPs in the migrant-by-migrant family and 429 significant SNPs in the resident-by-resident family, using an FDR-corrected p-value of 0.01. For the migrant cross, we located significant markers associated with 28 genes whose functions are connected to pathways previously hypothesized to be important in migration. Five genes on three chromosomes were associated with migration in both familial crosses, suggesting that these regions are important in determining life history regardless of familial origin in this population. These data will be further used to develop a model to predict life history in individuals that are yet to make that determination. Understanding the genetic factors involved in the decision to migrate, through the identification of polymorphisms associated with migration, will assist fisheries managers in restoring and maintaining migratory rainbow trout populations.

The Texas horned lizard (Phrynosoma cornutum) has always been believed to be an ant specialist, especially on harvester ants. However, a population of horned lizards in south Texas seem to have a more diverse diet consisting of other insects and arachnids. The goal of this project is to build a DNA library of order Coleoptera (beetles) that are preyed upon by these horned lizards. This DNA library will be compared to DNA extracted from horned lizard scat so that we can identify which species of beetles these lizards are eating. For this process, I isolated DNA from 244 beetles collected in pit fall traps from Kenedy and Karnes City, amplified the cytochrome oxidase I (COI) gene, and sequenced it. I compared the processed sequences to those available on GenBank and BOLD (Barcode of Life Database) to identify the species of beetle.

For several years, Texas horned lizards (Phrynosoma cornutum) in Kenedy and Karnes City (TX) have been the subject of ongoing studies at TCU. In the past decade lizards have disappeared from multiple locations in these towns, suggesting these populations are declining. To determine whether these populations have been stable or are declining in recent years, I used ArcGIS software to map GPS coordinates and calculate spatial statistics of horned lizards, their fecal pellets, and harvester ant mounds from 2013-2016. Stable spatial statistics across this time period should correlate with population stability at these sites.

Over the past century, millions of hectares of tropical rain forest have been cleared due to logging and agricultural endeavors. In addition to direct effects to terrestrial systems, conversion of land for agricultural use alters inputs to watersheds and has indirect effects on surrounding aquatic communities. Stream macroinvertebrates, which are often used as indicators of ecosystem health, can experience substantial changes in species composition as a result of these watershed alterations. We sampled macroinvertebrates from riffles and pools in a small stream with agricultural headwaters near the TCU El Jamaical Field Station in Costa Rica. We identified invertebrates to the lowest taxonomic level, and compared species abundance, richness, diversity, and evenness between riffles and pools. The high water quality and presence of bioindicator species suggest that this stream has been relatively unaffected by anthropogenic ecosystem alterations

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.

ClpX is a regulatory ATPase that functions along with ClpP as part of the intracellular bacterial ClpXP protease. Previous research from our group has shown that genetic loss of ClpX (∆ClpX) in Bacillus anthracis Sterne increases susceptibility to antimicrobial agents that target or interact with the cell wall including penicillin, daptomycin, and LL-37. In order to gain a better understanding of ClpX function in B. anthracis Sterne, a microarray analysis comparing WT and ∆ClpX gene expression was performed in B. anthracis. We found that LrgAB, a negative regulator of autolysis, was significantly downregulated in the ∆ClpX mutant and this finding was confirmed with QPCR. In order to determine whether LrgAB also had a role in antibiotic resistance in B. anthracis, we made a genetic deletion of LrgAB (∆LrgAB) and found it has similar phenotypes to ∆ClpX in B. anthracis. To see if these findings were consistent in other gram- positive pathogens, we expanded our research to Staphylococcus aureus, the leading cause of skin and soft tissue infections. We constructed a ∆ClpX mutant in the Newman strain of S. aureus and found it also exhibited sensitivity to cell wall active antimicrobial agents. Loss of ClpX in S. aureus also resulted in decreased expression of LrgAB by QPCR. Lastly, we examined a S. aureus ∆LrgAB mutant and observed an increase in antibiotic susceptibility. We conclude that ClpX plays a role in resistance to cell wall active antimicrobials in both B. anthracis and S. aureus, and that this is connected to its regulation of LrgAB.

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.

Breast cancer is a growing problem in the United States and worldwide. It takes the lives of approximately 40,000 U.S. women a year. 1 in 8 U.S. women will develop breast cancer during the course of their lifetime and it continues to be the most commonly diagnosed cancer in women. Clearly, this is a serious issue that must be solved. Current chemotherapy treatments often result in widespread cell death, including the killing of healthy cells. Therefore, it is necessary to find alternative treatments that specifically target cancer cells. Many breast cancer cells over express estrogen receptors, which are vital to the rapid cell division and growth of tumors. Estrogen is a steroid hormone that enters the cell, binds to its receptor, translocates to the nucleus, and leads to gene expression. Previous work from our group has resulted in the development of a drug which targets estrogen receptor positive breast cancer cells called Est-3-Melex. The drug contains a DNA methylating group (Melex) conjugated to estrogen. The mechanism of action of the drug is by the binding of the estrogen portion of the molecule to its receptor that ultimately translocates to the nucleus. While in the nucleus, the Melex portion of the compound is brought in close proximity to the DNA and methylates the adenines, eventually resulting in cell death. Essentially, this is a receptor targeted cancer therapy. In order to test the toxicity of this drug, we utilized a MTT cytotoxicity assay, which quantifies the amount of cell death. Est-3-Melex was more toxic to cancer cells that overexpressed the estrogen receptor compared to those that did not. Treating the estrogen receptor positive breast cancer cells with excess amounts of estrogen inhibited Est-3-Melex-induced cell death. Fluorescence imaging was also utilized to visualize localization of the drug. A fluorescent tag was attached to Est-3-Melex and introduced into estrogen receptor positive breast cancer cells. The results showed the drug localized to the nucleus and this localization was inhibited by estrogen. Our results suggest that Est-3-Melex is effective in specifically killing estrogen receptor positive breast cancer cells by binding to the estrogen receptor. Additional investigations are underway to identify the mechanism of cell death.

The effects of the thyroid axis on metabolism, growth, and development are well documented. However, there is a paucity of information on the role of thyroid hormones in the development of the immune system. Therefore, the goal of this study was to determine the effects of early life stage exposures to thyroid-altering chemicals on the developing immune system using the fathead minnow (Pimephales promelas) as the model, an organism commonly used in toxicity testing. This was accomplished by measuring differential expression of several immune-related genes in fish exposed to various doses of propylthiouracil (PTU, a thyroid-inhibitor) and thyroxine (T4, a thyroid-stimulator) sampled at 7 and 35 days post hatch (dph). Fish exposed to PTU exhibited significant increases in rag2 expression at 7 dph, decreases IgLC1 expression of at both 7 dph and 35 dph, and decreases in IgLC3 expression at 7 dph. In contrast, T4-exposed fish showed elevated rag1 and rag2 expression at both 7 and 35 dph, increased IgLC2 expression at 7 dph, and upregulation of ikaros at 35 dph. The results of this study indicate that exposure to thyroid altering chemicals influences the expression of several genes associated with proper immune system development, indicating that thyroid hormones regulate various aspects of immune development. These findings provide evidence that exposures to environmentally-relevant compounds that modulate thyroid function may lead to improper immune system development, which is likely to adversely affect overall organism health.

Recent research has identified dung beetles as bioindicator species found in a wide range of environments. Bioindicators function as monitors for the health of an ecosystem, which can be determined by analyzing the function, population, or status of the species in said environment. The purpose of our project was to determine if dung beetle diversity and abundance differed between primary and secondary rainforests. We conducted a study in the transition zone between tropical wet forest and premontane rainforest at the El Jamaical Field Station in Costa Rica. We acquired feces from both cows and horses near the field station. For trial 1, we made four bait traps using cow feces and one control for each of the forest types. Within each forest type, we placed the bait traps 25 meters apart. We then repeated the experiment using horse feces for trial 2. Traps sat for a period of 24 hours to allow dung beetles time to burrow into the traps. We then collected and processed the samples. Processing consisted of sifting and breaking down the feces in a meticulous manner to find, collect and identify all dung beetles present. We identified a total of 303 beetles in trial one and 0 in trial 2.

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.

Mercury (Hg) is a hazardous contaminant that can be transferred from aquatic to terrestrial environments by emerging aquatic insects. Terrestrial predators, such as spiders, that live along shorelines of water bodies may consume emerging aquatic insects and become contaminated with Hg. Mercury-contaminated spiders may pose a risk to arachnivorous songbirds. The degree to which most families of spiders are contaminated with Hg and the risk they pose to songbirds is not well understood. The objectives of this study were to determine 1) Hg concentrations in two families of shoreline spiders (long-jawed orbweavers, [Tetragnathidae] and crab spiders [Thomisidae]) and 2) determine the risk these spiders pose to arachnivorous birds. We collected representatives from two families of spiders from the shorelines of 10 ponds located at the LBJ National Grassland in north Texas, USA. Both spider taxa in the present study were contaminated with Hg, however long-jawed orb weavers had significantly higher concentrations of Hg in their tissues than crab spiders (p < 0.001; average Hg concentration = 346 ng/g and 35.7 ng/g respectively). We calculated wildlife values for various songbirds to determine health risks that these Hg-contaminated spiders may pose to songbirds. Spider-based wildlife values revealed that one of the families of shoreline spiders, Tetragnathidae, had concentrations of MeHg high enough that they may pose a risk to arachnivorous songbirds that consume spiders along the shorelines of ponds.

Mercury (Hg) is a toxic environmental contaminant formed in aquatic systems by bacterial methylation of inorganic mercury deposited from the atmosphere. Historically Hg contamination of food webs was thought to be restricted to aquatic systems. However recent research has shown that emergent aquatic insects such as dragonflies are contaminated with Hg as aquatic larvae, and then transport it to terrestrial ecosystems when they emerge from the water as adults. Terrestrial predators such as birds can be contaminated with Hg when the consume Hg-contaminated dragonflies. Because dragonfly larvae are top predators in aquatic systems, they contain high concentrations of Hg when they emerge from aquatic systems and can potentially pose a threat to the health of birds that feed on them. The objective of this study was to estimate the Total Hg (THg) concentrations in dragonflies across ecoregions in the South Central U.S. and the hazard Hg-contaminated dragonflies pose to dragonfly-consuming birds. I estimated THg concentrations in dragonflies by using published data on THg concentrations in predatory fish (pF) in 14 ecoregions and converting it to THg concentrations in gomphid dragonflies (gD) assuming a linear relationship (gD) = 0.0856(pF) + 25.92 constructed using data from Haro et al. 2013. The variation of predicted dragonfly THg was mapped by ecoregion using GIS software. GIS analysis tools were used to assess the risk the predicted THg in dragonflies that would pose a health hazard to dragonfly-consuming red winged blackbirds (Agelaius phoeniceus) in each ecoregion.