It is commonly understood that as we age, memory tends to decline. Memory failures can have severe consequences for older adults if they forget important things, such as taking daily medication. Recently, researchers have found that younger and older adults tend to remember forgotten information as having been less important than remembered information (Castel et al., 2012; Witherby, Tauber, Rhodes, & Castel, in prep). This effect is called the forgetting bias. In the present experiment, we investigated why older and younger adults show the forgetting bias.
Older and younger adults studied words that were assigned a value indicating the importance of remembering the word. Following study, they took a free-recall test. After repeating the study-test procedure four times, participants took a surprise test. On the test, they were shown each word and asked (1) if they remembered it on the free-recall test and (2) to recall the point value assigned to it during the study phase. Younger and older adults used their memory judgment on the surprise test as an anchor for recalling the value. Specifically, words that were judged as remembered were given high values, whereas words judged as forgotten were given low values. Thus, one reason why both older and younger adults show the forgetting bias is because they rely on their memory of past test performance. Future work is needed to examine whether a forgetting bias is shown with more meaningful information as well as ways to eliminate the bias.
The purpose of this study was to test the hypothesis that overt or covert echoic responding in the presence of an image is necessary for learning new verbal labels from exposure to contiguous presentations of words and images. (Horne & Lowe, 1996). This hypothesis predicts that seeing an image after hearing the associated verbal label leads to superior recall compared to seeing the image only before the verbal label is heard. Four children (3-6 years old) participated in a single-case design study that used an alternating-treatments design to evaluate the effects of stimulus presentation arrangement on subsequent recall of verbal labels. Each participant was exposed to six sessions that alternated across two conditions; word-first and image-first. In each session, the participants observed 20 pictures of four novel birds paired with their spoken names. In the word-first condition, the word and image were presented simultaneously but the image remained on the screen after the offset of the verbal stimulus. In the image-first condition, the image was initially displayed by itself, followed by the verbal label and the simultaneous offset of both. After each session received test for both verbal recall and recognition of the bird names. Compared to a prior experiment that was identical except that there was no overlap between image and word presentation, participants in the current experiment performed with slightly greater accuracy on the recall and recognition tests, but typically recalled only one or two labels after each session, with no difference between the image-first and the word-first condition.
Introduction: When faced with a potential stressor, such as having a child with autism spectrum disorder (ASD), individuals use coping strategies to adjust to the situation. Certain coping strategies are more adaptive, such as positive reframing, which is related to lower levels of depression for parents of children with ASD (Hastings et al., 2005). However, there are differences in coping between mothers and fathers, and possibly between non-Hispanic White and Hispanic parents as a result of cultural differences (Hastings et al., 2005; Willis et al., 2016). Therefore, the goal of the current study was to investigate which adaptive coping strategies moderated the relationship between child symptom severity and parent mental health for both non-Hispanic White and Hispanic fathers of children with ASD.
Method: Participants were 75 fathers of children (M = 6.64 years, SD = 2.29 years) with ASD, and were either Hispanic (n = 43; M = 41.77 years, SD = 6.75) or non-Hispanic White (n = 31; M = 44.35 years, SD = 6.25). All fathers completed the current version of the Social Communication Questionnaire regarding their child’s symptom profile. They also completed the Center for Epidemiological Studies Depression Scale, a measure of adult depressive symptoms, and the Brief COPE, a measure of frequency of coping strategy use. Separate moderated regression models were entered in the PROCESS macro for SPSS for fathers of each ethnicity with each of the following coping strategies: positive reframing, active coping, planning, instrumental use of social support, and religious coping.
Results: For non-Hispanic White fathers, there was a significant interaction (i.e., moderation) between the effects of child symptom severity and use of positive reframing on the parent’s depressive symptoms, b = -.43 (SE = .17), p = .02. The interaction accounted for an additional 15.6% percent of variance in depressive symptoms. For fathers who infrequently used positive reframing, there was a significant positive relationship between child symptoms and parent depression, b = 1.01 (SE = .36), p = .01, but the relationship was non-significant for those who used high levels of positive reframing, p > .05. Moderation was also found with instrumental support coping, b = -.38 (SE = .11), p = .003, R2 = .26, and religious coping, b = -.46 (SE = .14), p = .004, R2 = .26. However, neither active coping nor planning coping were significant moderators for non-Hispanic White fathers, ps > .05. For Hispanic fathers, none of the aforementioned coping strategies served as a moderator of the relationship between child symptoms and parent depression, ps > .05.
Discussion: Results suggest that using adaptive coping strategies frequently serves as a protective factor for non-Hispanic White fathers’ mental health. Therefore, teaching those fathers adaptive coping strategies may improve their functioning. Previous interventions increased use of adaptive coping strategies in parents of children with ASD and may be applicable in the case of fathers, as well (Samadi, McConkey, & Kelly, 2013). However, it may be that there is some other factor besides coping strategy use, which serves as the best protective factor for Hispanic fathers. For instance, future research may investigate the importance of family functioning, given the importance of familism in Hispanic culture.
Hastings, R. P., Kovshoff, H., Brown, T., Ward, N. J., Degli Espinosa, F., & Remington, B.
(2005). Coping strategies in mothers and fathers of preschool and school-age children
with autism. Autism, 9, 377-391. doi: 10.1177/1362361305056078
Samadi, S. A., McConkey, R., & Kelly, G. (2013). Enhancing parental well-being and coping
through a family-centred short course for Iranian parents of children with an autism
spectrum disorder. Autism, 17, 27-43. doi: 10.1177/1362361311435156
Willis, K., Timmons, L., Pruitt, M., Schneider, H. L., Alessandri, M., & Ekas, N. V. (2016). The
relationship between optimism, coping, and depressive symptoms in Hispanic mothers and fathers of children with autism spectrum disorder. Journal of Autism and Developmental Disorders, 46, 2427-2440. doi: 10.1007/s10803-016-2776-7
The importance of cannabinoid receptors has risen in recent years due to the increasing number of states that have legalized marijuana; 28 states allow the usage of medical marijuana and 7 states allow recreational use ("28 Legal," 2017). Previous research from our lab has explored coping with multiple instances of reward loss when exposed to large, chronic doses of cannabinoid agonist WIN 55, 212-2 (WIN, 10 mg/kg). When chronically exposed rats received a consummatory successive negative contrast (cSNC) downshift of 32% to 4% sucrose, they were less able to cope with the subsequent autoshaping downshift of 12 pellets to 2 pellets. Additional autoshaping research from our lab has shown multiple downshifts in autoshaping to be successful in obtaining contrast effects. The present research combined this procedure with occasional acute doses of WIN (1 mg/kg) to determine if only one kind of downshift experience, autoshaping, was sufficient to produce less coping efficacy if repeated. Rats were randomly assigned to either WIN or vehicle control groups, and then trained in acquisition with discrete lever presentations where one lever was always followed by the delivery of 12 pellets, and a second lever was always followed by 2 pellets. After acquisition, rats received downshift sessions once per week, wherein the lever previously associated with 12 pellets was downshifted to only be followed by 2 pellets. Prior to each of 4 downshift sessions, rats received intraperitoneal injections of either WIN or vehicle solution. Lever presses to each lever during discrete “forced choice” and simultaneous “free choice” trials and head entries into the cup where food was delivered, or “goal entries,” were both recorded to assess preference and explore downshift effects. Although acute WIN administration did not affect lever preference relative to vehicle controls, it did result in decreased lever pressing in favor of goal tracking during the downshift. Therefore, WIN seems to encourage rats to be more focused on the outcome instead of responding to signals for the outcome, which may have implications for reducing impulsive behavior despite extensive training.
Prior work has found that religious individuals experience greater concerns about mortality when thinking about Jesus taking human form (Arrowood & Cox, 2018). Building on this, the present research examined how intrinsic religiosity (i.e., a more “mature” form of religion with a development for a deeper, more meaningful relationship with God) would moderate these effects. Christian individuals were asked to complete the Religious Orientation Scale, followed by reading an essay that either described Jesus as being fully human or a description of His lost years (i.e., neutral condition). The dependent variable consisted of people’s fear of mortality. The results revealed that low intrinsic individuals experienced a heightened fear of death following a creaturely Jesus prime. High intrinsic individuals, however, did not differ from neutral conditions. This study suggests that intrinsically valuing religion can serve as a buffer against existential anxieties stemming from humanistic concerns.
Anxiety disorders are a widespread and serious health concern currently affecting approximately 18% of the adult population per year (Kessler, et al., 2005); thus, there is a strong need to develop and improve therapeutic treatments for anxiety. Moreover, because sex differences in the prevalence of affective disorders in humans are well documented, this study involves both male and female rats. Vocalizations allow for a dynamic assessment of an animal’s emotional state. The ultrasonic vocalizations (USVs) of rats are produced at frequencies above the level of human hearing. USVs are often used as a tool to assess the emotional state of rats. Previous research has identified two main call types for rats: 22 kHz (related to strongly negative emotion) and 50 kHz. 50 kHz calls can then be further broken down into constant frequency (CF) and frequency modulated (FM) subtypes. FM calls are produced with a bandwidth greater than 15 kHz; these calls are related to positive emotional states. Whereas, CF calls are produced with a constant frequency and a bandwidth less than 10 kHz. Our lab hypothesizes that CF 50 kHz calls are expressions of anxiety in rats. Our lab has previously explored the vocalizations of rats across a continuum of negative affective state (i.e., from anxiety to fear) within a single testing session using a sequence of temporally consistent mild footshocks. The current experiment explores USV production in male and female rats when the temporal predictability was reduced by randomizing the time between footshocks. We utilized an unpredictable footshock paradigm with the goal of increasing or prolonging a state of anxiety as compared to our previous procedure. In this paradigm, shocks were administered across three successive days: on Day 1, mild footshocks were administered in a pseudo-randomized pattern, on Day 2, subjects were returned to the same context but did not receive footshocks, and on Day 3, a single reinstatement shock was administered. Differences in USV calling behavior across test days will be explored in male and female rats. In addition to USVs, rearing and freezing behavior were also recorded and used to assess anxiety and fear. These results will enhance our understanding of vocal expression of emotional states in rats, which improves the dominant animal model used to study anxiety disorders and potential therapeutic interventions.
Discrimination learning involves responses (e.g., cheering for TCU) that are rewarded under some conditions (e.g., at a TCU football game) but not others (e.g., in the library). Occasion setting involves a higher-order discrimination in which one stimulus (i.e., the occasion setter) signals whether response to a second stimulus (i.e., a discriminative stimulus) will be rewarded (e.g., followed by food) or not. In the current experiments, pigeons were trained in a spatial occasion setting task in which an occasion setter (i.e., a colored background) provided information about if and where to respond relative to a discriminative stimulus that served as a landmark (i.e., a colored box embedded within the occasion setter). These experiments examined the effect of spatial ambiguity on occasion setting. In Experiment 1, pigeons were trained on a task in which spatially stable occasion setters gave information about where to respond relative to spatially unstable landmarks (←YB, ZB→, ←WA, XA→, ←C→). In Experiment 2, a different set of pigeons were trained with both a spatially unstable and two spatially stable occasion setters paired with landmarks that were spatially unstable (←WA, WB→, ←XA, YB→, ←C→). Transfer tests showed that the stable occasion setters were able to control responding to spatially unstable landmarks that they had not been paired with in training.
In a delayed serial same-different discrimination procedure, one stimulus is followed by either the same or a different stimulus after a brief delay. To receive reinforcement (e.g., food), the subject must respond “same” when the two stimuli match and a “different” response when they differ. The individual stimuli change across trials, so it is the relation between stimuli that signals the correct response. A differential outcomes procedure has been shown to facilitate learning of some discriminations but had not been tested with rats in a relational discrimination. In a differential outcomes procedure, one reinforcer (e.g., pellets) follows one response (e.g., a correct “same” response) and a different reinforcer (e.g., sucrose) follows another correct response (e.g., a correct “different” response). In the control condition, the same reinforcer follows a correct “same” and “different” response. In the current experiment, half of the rats were trained on a serial same-different discrimination using a differential outcomes procedure and the other half were in the control group. Stimuli were presented and responses recorded on an iPad mounted at the rear of an operant box. After the rat touched the sample stimulus (i.e., the first stimulus) it was removed for a delay of 500, 1500, 3000, or 6000 ms before the rats were presented with the comparison stimulus (i.e., the second stimulus). After touching the comparison stimulus, a response button appeared on each side of it. One button represented a “same” response and the button on the other side a “different” response. After training, rats were tested to determine if learning of the same-different relation would transfer to novel stimuli. The results showed no transfer of learning, and a decrement in performance on trials with the original training stimuli.
Individuals with Autism Spectrum Disorder (ASD) tend to have difficulties with emotional and social interactions (e.g., Stone & Caro-Martinez, 1990). It is possible that they also have deficits in their ability to monitor their learning of social and emotional information. If so, this could have negative downstream effects on their later memory. In the present experiment, we investigated the influence of social and emotional pictures on adolescents’ (with and without ASD) monitoring of learning and memory performance. To do so, participants studied 60 pictures that were positive or neutral and that either had a social component (e.g., a couple at their wedding, a child reading a book) or did not (e.g., ice cream, screwdriver). After studying each image, participants made a judgment of learning (JOL) predicting the likelihood that they would remember that picture on a later test. Finally, participants took a free-recall test. Overall, adolescents with ASD provided lower JOLs and demonstrated lower memory performance than did adolescents without ASD. In addition, all participants gave higher JOLs to positive pictures than to neutral pictures, and recall was also superior for positive relative to neutral pictures. Finally, participants gave higher JOLs to pictures with a social component than to pictures without a social component, although this dimension did not influence their memory. These results suggest that monitoring of learning is not impaired in adolescents with ASD. Thus, although adolescents with ASD tend to remember less than adolescents without ASD, this finding does not appear to be caused by monitoring deficits.
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.
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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.
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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.
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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.
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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.
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Mercury (Hg) is a highly toxic environmental contaminant found in all waterbodies on earth. Emergent aquatic insects (like mosquitoes) transfer Hg from the aquatic systems to terrestrial consumers such as spiders. The objective of this study was to examine Hg concentrations in larval mud daubers (Sceliphron caementarium) and their spider prey in mud dauber nests. Adult mud daubers capture spiders with a paralyzing sting to use as the food source for the larvae in their nest. I collected 350 mud dauber nests from three bridges on the Trinity River and one building 40 m inland from the Trinity River in Fort Worth, TX. The nests contained 74 mud dauber larvae and over 2,000 spiders of five different families. I used a Direct Mercury Analyzer to determine the total Hg concentration of mud dauber larvae and five spider taxa. All mud dauber larva and spiders were contaminated with Hg. The inland site had the lowest concentration of Hg in the spiders, suggesting that the spiders at this site were more reliant on low Hg terrestrial prey than high Hg aquatic prey. This is the first study to demonstrate that mud daubers nesting along river systems are part of the mercury cycle because of their use of shoreline spiders as prey for their larvae.
Leaf cutter ants are the rainforest’s most prolific herbivore, eating more vegetation than any other type of creature. The ants have a profound effect on the Neotropical ecosystem, for they improve the richness of the soil, and, by removing leaves from the trees, allow sunlight to reach the lower levels of the forest, facilitating plant growth and diversity. Leaf cutter ants are selective in the plant materials they harvest. The goal of this study is to determine whether leaf cutter ants have a preference for fragile versus tough leaves by examining the relationship between level of leaf damage by leaf cutter ants and leaf toughness among a number of plant species. Leaves damaged by leaf cutter ants of several plant species were identified and collected from the trails of two ant nests in El Jamaical Field Station in Costa Rica. Area of leaf cutter herbivory were traced and recorded as the measurements for level of leaf herbivory. Leaf toughness was quantified as the force required for tearing the leaf apart by using a gravity-based tearing device. From the obtained data, we will examine the level of leaf herbivory of each leaf of the same species against its toughness to see whether leaf cutter ants prefer cutting fragile leaves over tough leaves in order to minimize energy cost. We will also compare this foraging pattern between species to see whether there is a variation in the ants’ preference among different plant species.
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.
Over the last few decades, there has been increasing concern regarding the environmental presence and biological effects of endocrine disrupting compounds. Studies aimed at determining the adverse impacts associated with exposures to thyroid disrupting compounds have focused primarily on the ability of such compounds to alter patterns of growth and development; however, the actions of thyroid hormones extend well beyond these basic functions. As such, there is a need to investigate the potential for thyroid disrupting compounds to alter other physiological processes. Recent studies have suggested a role for thyroid hormones in the regulation of immune function. As such, it is reasonable to suspect that exposure to endocrine disrupting chemicals that impair thyroid activity will lead to alterations in immune function and subsequent changes in pathogen and disease resistance. Using the fathead minnow (Pimephales promelas) as a model organism, this study sought to determine the impact of propylthiouracil (PTU, a known thyroid inhibitor) on various aspects of immune function including immune gene expression, spleen index and pathogen resistance. To achieve this, male fathead minnows were divided into two groups – a control and a PTU-exposed group. Following a 21day exposure period, both groups were challenged with the pathogen Yersinia ruckeri, and mortality was monitored for 14 days to assess pathogen resistance. In addition, tissues (i.e., liver, spleen and kidney) were sampled at 8 hours and 72 hours post infection for the assessment of immune gene expression and spleen index. PTU exposed males were less able to survive pathogen infection relative to the controls. In addition, PTU-exposed males had significantly lower spleen index than the controls following injections, suggesting that they had a reduced ability to elicit an immune response. Gene expression of certain immune genes also showed a change in pattern of expression, signifying potential pathways and proteins that are particularly affected by thyroid hormone presence. These results show that chemically-induced decreases in thyroid hormone levels can suppress immune function and demonstrate that the immune system is a target for thyroid disrupting chemicals.
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.