How does one decide to act? In humans, the “decision” to initiate a behavior can occur several seconds before an action is undertaken and can even occur without conscious awareness. Here we explore whether we can predict when a nonhuman animal is going to engage in a self-initiated behavior.
Singing in songbirds is a learned behavior that is passed down from one generation to the next via imitative learning. Birds initiate song in response to the presentation of a female bird (directed) or spontaneously when in isolation from other birds (undirected). The production of song requires the control of respiratory, vocal organ, and upper vocal tract motor systems; these diverse motor systems are controlled by the activation of precise neural networks within specific areas of the songbird brain. Although much is known about the neuromuscular control of song, the neural and peripheral mechanisms underlying song initiation and termination have received less attention. Here we explore in two songbird species whether song initiation and termination can be predicted by measuring changes in respiratory patterns prior to, during, and after song. We quantified changes in respiratory rate and amplitude, as well as changes in time spent in the inspiratory versus expiratory cycle to determine whether specific features of respiration were tied to onset or offset of song. Measurements of respiratory patterns were undertaken in zebra finches (Taeniopyggia guttata) and Bengalese finches (Lonchura striata var. domestica). Preliminary data suggest that respiratory patterns change predictably within the last second prior to when a bird initiates song. Following song, there is clear evidence of respiratory changes due singing-related exertion. Our findings illustrate that the occurrence of self-initiated behaviors can be predicted by exploring peripheral song motor control up to one second prior to the onset of the behavior. These results illustrate that the decision to act can be predicted by changes in peripheral motor systems which likely serve as preparatory activity for the upcoming motor action.

Moral injury is the psychological or spiritual consequence of acting (or failing to act) in a manner that is inconsistent with one’s moral code (Litz et al., 2009; Shay, 1994). The goal of this research was to test a spiritual resilience training program on those with moral injury and their perceived stress and growth. We administered a survey of 21 psychologically validated scales to veterans before the training sessions and one week apart after they ended. Specifically, we were interested in seeing how those who completed a one-week training program would respond to measures of perceived stress, post-traumatic growth, and moral injury, as compared to a control group that did not complete the training. Those who completed the training went through a program of group discussion, journal activities, art therapy, and individual reflection. We found that veterans who completed the program had higher ratings of: post-traumatic growth, relating to others, and sense of spirituality. There were no differences in self-reported perceived stress. The results of the current study could provide more insight into how the training program works and if the program assists veterans in acclimating to life after possible traumatic events during deployment.

Past research in evolutionary psychology has found that women experience shifts in their mate preferences during ovulation - the few days in a month in which conception is possible. Specifically, ovulating women show an increased preference towards men with greater levels of masculinity, facial symmetry, and creative ability. These traits are thought to be indicators of a high-quality mate, and as such women are thought to be attuned to these traits when conception is possible. To extend this research, we sought to examine whether this effect was driven by changes in women’s abilities to detect subtle differences in these traits. To do so, we tested women’s ability to discriminate between mating related stimuli, including slight changes in facial symmetry and masculinity, gait masculinity, and creativity, at both ovulation and a low fertility point in their ovulatory cycles. We are collecting a sample of 240 women – 120 who are taking hormonal contraceptives, and 120 who are naturally cycling. We predict that ovulating, natural cycling women will be better able to detect subtle differences in mating related stimuli compared to naturally cycling, low fertility women, as well as those women taking hormonal contraceptives. Preliminary results will reveal if ovulating women are better able to detect these differences and if they are more attuned to the quality of potential mates.

One of the main hallmarks of Alzheimer’s disease (AD) is dramatic cognitive decline, including memory loss. Because of this, AD research continually seeks new ways to study the cognitive health of animal models of AD. Researchers have assessed cognitive deficits in AD mice through a variety of behavioral paradigms. The purpose of the present study is to assess if mice with AD-like markers display cognitive deficits in an additional behavioral paradigm, the Novel Object Placement (NOP) task. Animals are allowed to explore two identical objects in a testing arena for three sessions of five minutes. In a fourth session, one of the objects is moved to a different spot in the arena. Animals with intact cognition spend more time exploring the object in the novel location than the object in its original location, as mice naturally display a preference for novelty. Pilot data from our lab demonstrates that experimentally naïve animals complete the task successfully. The animals used in this study are 5xFAD transgenic mice, nontransgenic mice, and nontransgenic mice administered LPS. 5xFAD mice have genetic mutations that result in the production of a protein, amyloid beta, that is seen in human AD, and is often associated with cognitive deficits. Additionally, our lab has previously demonstrated that nontransgenic mice administered seven consecutive days of LPS, a bacterial mimetic, also produce amyloid beta. To investigate if both of these mice display deficits in NOP, we gave nontransgenic 5-6 month-old mice seven days of either LPS or saline injections, and we gave 5xFAD animals saline injections. For the next three days following the 7th injection, the animals were placed into the testing arena with identical objects in adjacent corners of the arena and allowed to explore. Four hours after the third training session, one of the objects was moved to a new location in the arena, and animals were placed back into the arena for the testing session. The dependent variable was the percentage of total object exploration time spent exploring the object in the novel location. There were no significant differences between the nontransgenic animals that received LPS or saline. However, the 5xFAD animals spent significantly less time exploring the novel object compared to the nontransgenic animals, indicating impairment identifying the novel object location. Therefore, at 5-6 months of age, the 5xFAD mice demonstrated cognitive deficits in the NOP task. Further research will explore at what age these cognitive deficits emerge and the extent to which various AD markers are correlated with the deficits.

In an effort to improve academic achievement, we examined the effects of meaning in life (MIL) on grade performance. Prior research has found that MIL is associated with better adjustment to stressful life events. Fall semester freshmen in general psychology courses were asked to complete measures of MIL and academic adjustment. At the end of the semester, their final grades from general psychology courses were collected from the Registrars’ office. The results revealed that higher meaning presence persons reported experiencing better academic adjustment to college. Higher adjustment was associated with increased end of the semester final grades in general psychology . No effects emerged in response to meaning search. These findings suggest that the presence of MIL in early college life could have important implications for academic well-being and achievement.

Alzheimer’s disease (AD) is a progressive form of dementia marked by decline in cognitive functioning and memory loss due to protein abnormalities in the brain. One early cognitive deficit seen in AD is a contextual acquisition deficit. However, evidence suggests that deficits in contextual extinction learning may present earlier than acquisition deficits. Extinction is a type of learning process by which the brain acquires information inconsistent with information it had previously learned, and gradually begins to accept this new information instead of the old. As psychological stress has been linked with increased Alzheimer’s markers, it is important to explore the interaction between stress and contextual learning.
In our first experiment, male C57BL/6J mice were divided into three groups – unpredictable stress (US), isolation, and group housed (controls). All three groups were trained in a contextual fear conditioning. After training, the animals in the isolation and US groups were isolated in individual cages for seven days. In addition to living in isolation, the US group underwent seven days of variable, unpredictable stressors which include 2 hours of wet bedding, cage tilted at 45 degrees for 30 minutes, 30 minutes of restraint stress, 5 minutes of forced swimming in warm water, placement in an empty cage for one hour, and nesting material removal overnight. These stressors were applied in a random order every day for 7 days. On the eighth day, acquisition learning was assessed. Animals in the US group showed significant deficits in acquisition of contextual fear conditioning compared to isolated animals and group housed controls. Extinction learning was assessed on days nine through twelve. There was no effect of US on extinction learning, as there was likely a floor effect due to impaired acquisition. In the second experiment, animals were divided into US and a group housed control group. The US animals underwent the same series of stressors listed previously for six days. On the seventh day, all animals received one 250mg/kg injection of LPS, a bacterial mimetic, to determine how stress impacted the immune challenge. Four hours later, the hippocampus was collected for cytokine and HMGB1 mRNA analysis. As the elderly face surmounting odds of AD, along with significant stress, research on how these interact and early diagnostic signs is especially relevant.

Reinforcer devaluation involves pairing an appetitive stimulus (e.g., food) with an aversive event (e.g., illness), which disrupts the ability of the stimulus to elicit behavior (Adamson & Dickinson, 1981). The effect of reinforcer devaluation could be the result of the stimulus signaling the aversive event. Alternatively, exposure to the stimulus and aversive event together may result in a hedonic shift, or change in the affective unconditional properties of the stimulus. The two accounts make different predictions regarding the effect of reexposure to the devalued stimulus. The hedonic shift account describes reexposure to the stimulus as necessary to experience the changed value of the stimulus, but a signaling account can explain devaluation after one pairing. Balleiene & Dickinson (1991) found that reexposure to food paired with illness was necessary to observe a devaluation effect. The current experiment investigated the devaluation of a conditioned reinforcer. Rats were initially trained with pairings of an audiovisual (light and tone) stimulus with sugar water (sucrose). In the next phase, acquisition of a new behavior, lever pressing, was supported by presenting the stimulus (conditioned reinforcer) following a lever press. During devaluation, the experimental group received one trial of the stimulus paired with a shock, whereas the control group received the stimulus and shock, but separated in time (i.e., unpaired). In Test 1, all rats were given the opportunity to press the lever with no nominal consequences (e.g., no stimulus or shock). Then, all rats were re-exposed to the audiovisual stimulus without the lever or shock. In Test 2, lever pressing was measured as in Test 1. The data will be discussed in terms of the role of reexposure in devaluation.

References

Adams and Dickinson (1981). Instrumental responding following reinforce devaluation. The Quarterly Journal of Experimental Psychology Section B: Comparative and Physiological Psychology, 33 (2), 109-121.

Balleine, B., & Dickinson, A. (1991). Instrumental performance following reinforcer devaluation depends upon incentive learning. The Quarterly Journal of Experimental Psychology, 43(3), 279-296.

There is empirical evidence that there is an association between nostalgia, or a sentimental longing for the past, and one’s psychological and social well-being. Additional research has shown that nostalgic reverie leads not only to increased optimism and positive attitudes towards preventative health behaviors, but also actual increased health behaviors. This study extends the research on nostalgia and health into the realm of college athletics and explores how collegiate athletes’ performance is correlated with nostalgic tendencies, in addition to various measures of well-being, optimism, meaning in life, vitality, and life satisfaction. A positive correlation is expected, such that higher performing athletes are also more nostalgia prone. This study will serve as a foundation to explore the direct benefits for athletes of nostalgic thought, the advantages of which are firmly supported in other contexts.

Covert echoing has been hypothesized to play a role in the emergence of stimulus control over vocal naming after a person is exposed to contiguous presentation of a novel object and its name. However, experimental evidence is weak. This study examined the effects of blocking echoic responses during exposure to name-object presentations on later vocal naming. Preschool-age children were exposed to pictures of national flags and heard the associated country names. In the echoic condition, participants were instructed to echo the country name presented in each trial. In the interference condition, they were instructed to name the background color on which the flag was presented in each trial, which was presumed to interfere with echoic responding. In the no-response-requirement (NRR) condition, participants were not instructed to make any responses. Flag naming was probed after each session. Only 3 of the 5 participants showed a tendency to name the flags vocally even after repeated exposure. Of these three, only one demonstrated poorer performance in the interference condition relative to the echoic and NRR conditions. These results fail to provide support for the echoic hypothesis and are consistent with other data from our lab.

Student evaluations of teaching (SETs) are a tool commonly employed at universities for assessing faculty members’ teaching performance and even eligibility for promotions. Survey items often ask students to make judgments about the professor’s knowledgeability, teaching style, and class difficulty. Fair and consistent review of SETs is critical for faculty members as they seek to improve their teaching skills and gain professional recognition. The present study investigates the novel question of how judgments of completed SETs are made. Undergraduate students (n = 160) and faculty participants were shown and asked to make judgments about a fictional SET. The four conditions varied in whether the fictional professor being evaluated was rated lower or higher than average, and whether or not the professor gave in-class quizzes. Follow-up questions had participants evaluate why they made certain judgments about the professor. This research helps explicate the factors that contribute to faculty members’ interpretations of and students’ responses on SETs.

In nature, it is adaptive for an animal to learn to make different responses to different stimuli (e.g., climb some trees to obtain ripe fruit but forage near the base of others). In the laboratory, learning to make different responses (e.g., lever pressing vs. chain pulling) is facilitated by different outcomes (e.g., food vs. water) for each response. The current research aimed to extend this differential outcomes effect in rats with a visual discrimination procedure. Rats were reinforced for pressing a lever on the left side (left lever) of operant box in the presence of one visual stimulus (e.g., a flashing light) and for pressing the right lever in the presence of another visual stimulus (e.g., a solid light). In the experimental group, the rats received a different outcome for each correct response (flashing light -> left lever -> sugar water; solid light -> right lever -> chocolate pellets). In the control group, the rats received only one of the outcomes (e.g., sugar water) for both responses. The data will be discussed in terms of support for the differential outcomes effect. Examining the effects of a differential outcomes procedure in a variety of tasks will help to better understand the conditions under which this effect can facilitate learning.

Few studies have directly evaluated the assumption that equivalence-based instruction establishes stimulus classes with greater efficiency than direct instruction of all possible stimulus relations within each class. Therefore, this study evaluated the efficiency of EBI protocol compared to direct instruction (DI), using fifteen visual abstract stimuli (A1 through E3). Forty-eight undergraduate students were assigned to one of four groups: The EBI-DI group received EBI in Phase 1 and DI in Phase 2, and vice versa for DI-EBI group. EBI-EBI and DI-DI group received EBI and DI in both phases, respectively. In Phase 1,EBI-first groups received training on AB and BC relations and DI-first groups received training with all possible relations. After achieving mastery criterion, the ABC test included all possible trial types. In Phase 2, all groups received training to (a) add a fourth stimulus (D), and (b) add a fifth stimulus (E) to the class. No statistically significant difference was found between EBI and DI-first groups in the number of trials, reaction time during test and overall trials to achieve criteria and the performance in ABC test. There was an interaction between the first training condition (EBI vs. DI) and the second training condition (EBI vs. DI) on percentage accuracy in the first ABCD test, but not in ABCDE test.

This study explored the extent to which nostalgia proneness (a sentimental longing for the past) is associated with attitudes towards intimate partner violence (IPV). Research has found that individuals who report more conflict in their romantic relationships also report being more nostalgic for their own and for their relationships’ past. If nostalgia is related to more conflict in relationships, then it may also be related to greater acceptance of IPV. In this study, a sample of 142 participants completed measures of self-relevant nostalgia, relationship-relevant nostalgia, and attitudes toward IPV (using it and enduring it), and relationship outcomes (e.g., optimism, satisfaction, commitment). Results showed positive correlations between nostalgia (self-oriented and relationship-centered) and self-use of IPV (both using it and enduring it). These preliminary results suggest that a sentimental longing for the past is associated with endorsement of IPV use, however, other unexplored personality variables such as attachment style may moderate these associations. Future work should explore these findings in experimental and longitudinal designs.

Investigating how people regulate their learning is important because study decisions can impact actual learning. Compared to younger adults, older adults often show age-related deficits in memory. This deficit may be because older adults are less effective at regulating their learning. One factor that can influence memory is the valence of information. Prior research has established that older and younger adults are more likely to recall emotional information compared to neutral information and also predict that emotional information will be better remembered relative to neutral information (e.g., Tauber & Dunlosky, 2012). It is unclear how both age groups regulate their learning of emotional and neutral information. Investigating this issue, older and younger adults studied words that were positive (e.g., circus), negative (e.g., snake), or neutral (e.g., fork). Participants regulated their learning by self-pacing their study (Experiment 1) or by selecting half of the words to restudy (Experiment 2). After studying each word, participants predicted the likelihood of remembering it on a scale of 0% (will not remember) to 100% (will remember). Finally, participants took a free-recall test. Consistent with prior research, both age groups demonstrated higher predicted and actual memory for emotional information relative to neutral. Importantly, both age groups’ self-paced study times did not differ for emotional and neutral information. In contrast, both age groups restudied neutral words more frequently than emotional words. Thus, when participants were forced to strategize their learning, both age groups made good study decisions, prioritizing neutral information at the expense of emotional information.

For my SERC grant proposal, I studied the effect of auricular vagus nerve stimulation (aVNS) on learning in adults with dyslexia. The vagus nerve is a cranial nerve that, when stimulated, initiates the release of two neurotransmitters (NT’s) that are important in learning and memory (norepinephrine and acetylcholine). When a stimulus is presented at the same time as vagus nerve stimulation, this increases neural plasticity for the paired item. We have already tested this approach on typically-developing adults using the auricular branch of the vagus nerve, which runs through the ear and can be stimulated non-invasively. During this intervention, timed bursts of electrical stimulation were delivered while the participant learned novel letter-to-sound correspondences for Hebrew letters with the goal of increasing recall and automaticity. We have already found significant improvements in letter recognition, reading speed, and nonword decoding in typically-reading participants receiving stimulation compared to those in control groups. Our ultimate goal is to help children with dyslexia read more fluently. In the first step towards this goal, we enrolled a group of adult participants with dyslexia who received 10 days of Hebrew orthography training paired with aVNS. Participants were evaluated at four timepoints to monitor learning and compare progress with other groups: at day 1, halfway through training, at the end of training, and 3 weeks after training ended. We measured letter recognition, letter-to-sound fluency, and decoding at each time point. We will present our preliminary findings at SRS and discuss future directions.

Early life stress has shown to be related to an increased preference for smaller, more quickly acquired rewards over larger, delayed rewards—or an inability to delay gratification—a fundamental component of impulsivity. Beyond this, impulsivity is also characterized by difficulty concentrating and exercising self-control and has been found to significantly impact learning and memory. Specifically, in children, higher impulsivity is associated with greater learning difficulties, such as with reading. Previous research has also shown that adults with higher levels of inflammation portray higher impulsivity. The current study aims to investigate the relationship between impulsivity, inflammation, and childhood environmental conditions within children between the ages of 3-17. Saliva samples were collected from 248 children visiting the Fort Worth Museum of Science and History in order to measure current levels of proinflammatory cytokines, which indicate immune activation. Children then participated in a series of tasks that measured their ability to concentrate, learn to inhibit their responses, and delay gratification, while background and demographic information was collected from their parents. Results will reveal whether children growing up in stressful environments also have higher levels of inflammation and impulsivity.

Attitude Representation Theory (Lord & Lepper, 1999) asserts that individuals evaluate attitudes based on a subset of associations. As this subset of associations varies, attitudes can vary as well. Previous research demonstrated that people can mistake self-generated information for provided information, through source monitoring errors (Johnson, Hashtroudi, & Lindsay, 1993), after extrapolating beyond the information given (Lu, 2015). We sought to apply ART and cognitive tasks (e.g., extrapolation, embellishment, and validity) by having participants judge the actions of fictitious groups. Although these groups are fictitious, they allude to current political viewpoints. We tested the effects of extrapolation (thinking about additional attributes of a target group; Experiment 1), embellishment (convincing a friend not to join the target group; Experiment 2), and biased assimilation (testing truth and validity of sources; Experiment 3) on polarization of moral judgments. Compared to a control group, embellishment polarized negative attitudes toward the group. The current set of studies could shed some insight about how people view issues, self-radicalize judgments, and understand thoughts of lone-wolf terrorists.

There are many benefits for children to receive music education. Research shows that note reading and music playing skills are positively correlated with cognitive development, motor proficiency, and self-esteem (Bilhartz, Bruhn, & Olson, 1999; Costa-Giomi, 2004; Schellenberg, 2004). The purpose of this study was to evaluate the use of equivalence-based instruction (EBI) to teach elements of music to children who have no music background in the age range of 4-7 years. The children first learned to relate the name of a note (e.g. “quarter”, “half”) to the length of the note as well as a picture of the note. They were also taught to name the lengths and names of sequences of notes (e.g. “quarter, quarter, half”). In the second part of this study, the children learned letter names of notes (e.g., “A”), keyboard placement, and what finger (e.g. thumb) goes with each letter name and piano key. Finally, we tested for emergent relations from part one and part two. Date collection in progress, but we predict to see emergence of relations between what was taught in part one and what was taught in part two. For example, when told “play this sequence on A,” participants will be able to use the correct finger on the correct piano key to play the notes in the sequence at the correct lengths.

Since the 1920s, it has been recognized that nonhuman animals are capable of forming expectations about rewards and exhibit emotional responses when those expectations are violated—when obtained rewards have lower value than expected rewards. Our lab utilizes a rodent model for coping with unexpected reward loss with a specific interest in furthering our understanding of the underlying neural correlates. Frustration effects in rats are commonly and reliably produced using the consummatory successive negative contrast (cSNC) procedure, where rats are given access to a highly preferred 32% sucrose solution followed by an unexpected downshifted to 4% sucrose. Such surprising nonreward leads to a suppression of behavior compared to a control group that always received the less-preferred, 4% sucrose solution. Studies involving neurological manipulation indicate that permanent lesion or reversible deactivation of the central amygdala (CeA) and the basolateral amygdala (BLA) eliminate the cSNC effect. While these studies are important for identifying key structures, they provide little information about the underlying circuitry. The present research examined the role of the neural pathway between the BLA and CeA in the cSNC task using a chemogenetic approach known as Designer Receptor Exclusively Activated by Designer Drugs (DREADDs). Inhibitory DREADDs are intracranially infused into the key structures and later activated by intraperitoneal injections of clozapine N-oxide (CNO). Both groups of rats received unilateral inactivation of the BLA and CeA. The experimental (contralateral) group has one functioning area in each hemisphere, a procedure that disrupts communication between the two areas. The control (ipsilateral) group has one hemisphere disrupted while the other is left intact. Preliminary results indicate a disconnecting the BLA-CeA pathway reduces the cSNC effect in contralateral rats compared to ipsilateral rats. The BLA-CeA pathway is necessary to respond to surprising nonreward. These results add to the hypothesized model of circuity underlying unexpected reward loss in mammals. Because the amygdala circuitry is highly conserved across species, these results inform us about the neural circuitry engaged by similar instances of frustrative nonreward in the human brain.

According to Terror Management Theory, religious people are motivated to cling to their religious beliefs when reminded of their death. Quest motivated religious people, however, value doubt in their beliefs and are uncertain about the validity of their religion. The purpose of the present work was to examine medical decision making among individuals who actively question their religious beliefs when death concerns are salient. Specifically, we found that individuals who are quest motivated reject traditional faith healing in favor of more scientific medical practices. These effects were exacerbated by death awareness. These findings support previous research suggesting that quest individuals are motivated to embrace their religious doubts in when faced with existential concerns.

Hepatitis C Virus is estimated to infect 3% of the world’s population and is transmitted by contaminated blood. HCV can be asymptomatic or lead to cirrhosis of the liver, liver cancer or hepatocellular carcinoma. Understanding the virus life cycle and the viral proteins generated by HCV will help generate new mechanisms of inhibition of the virus. HCV produces 10 viral proteins when it infects hepatocytes that increase the reproduction ability of the virus. The anti-viral response of the body uses transcription factors such as ATF-2, NFKB, and IRF-3 that translocated into the nucleus and bind to the interferon gene that produces interferon to alert the body of a viral infection. HCV viral protein NS3/4A acts as protease to cleave the polycistronic strand of viral proteins made by HCV and is known to inhibit IRF-3 movement into the nucleus to inhibit the production of interferon. HCV viral protein NS5A is known to inhibit the movement of transcription factor NFKB into the nucleus, thus inhibiting the anti-viral response. We are interested to see if NS3/4A inhibits the anti-viral response by blocking the movement of both transcription factors IRF-3 and NFKB into the nucleus.

Psychological stress afflicts a considerable portion of the world’s population, and is linked, as both a risk factor and potential contributor, to dementia-related brain dysfunction in diseases such as Alzheimer’s disease (AD). The brain dysfunction in AD is marked by an increase in Amyloid-beta, the protein responsible for plaque deposition in the brain. The present study aimed to explore alterations in the production of amyloid-beta in response to stress and inflammation. Specifically, we were interested in social isolation stress- and inflammation-induced differences in cognition and amyloid-beta production in male and female mice. Mice were subjected to acute social isolation (6 days) and chronic isolation (28 days) or control group housing. Results revealed that exposure to both acute and social isolation can lead to an exacerbated inflammatory response to lipopolysaccharide (LPS). Subsequently, we examined if the stressors altered amyloid-beta production following the same inflammatory stimulus. Animals received LPS or saline injections once per day for seven consecutive days after the completion of either stress protocol or group housing. The contextual fear conditioning paradigm (CFC) was utilized to assess cognition. Brain tissue extractions were performed to quantify amyloid-beta protein levels. It is hypothesized that isolated animals will demonstrate cognitive deficits in CFC as well as increased brain amyloid-beta following LPS injections.

Hydrilla verticillata is an invasive aquatic weed in the United States (U.S.) that has recently
developed resistance to the herbicide fluridone. In this study, we utilized genome walking and
quantitative real-time PCR to investigate the phytoene desaturase (PDS) gene copy number of
hydrilla samples with different ploidy levels. We asked 1) if copy number simply corresponds to the
ploidy level, and 2) if there is increased PDS copy number in resistant populations due to gene
duplication. Using qPCR and microsatellite loci to compare PDS copy number between diploid,
triploid and tetraploid samples, we found that diploid hydrilla from Africa showed higher PDS copy
number than triploid populations from the U.S. The results also indicated that there was no
significant difference in PDS gene copy numbers between the fluridone-resistant and -susceptible
triploid populations. Our study suggests that PDS amplification may not be a mechanism
responsible for fluridone resistance in hydrilla.

Methylmercury (MeHg) is a toxic environmental contaminant found in all waterbodies on Earth. Aquatic emergent insects, such as mosquitoes and midges, can transfer MeHg from waterbodies to terrestrial ecosystems. Terrestrial shoreline spiders consume aquatic emergent insects and become contaminated with MeHg. Methylmercury-contaminated spiders can pose a risk to songbirds that consume terrestrial spiders. Because shoreline spiders have MeHg concentrations that reflect MeHg contamination of nearby aquatic ecosystems and are an important source of MeHg to songbirds, they have been proposed as a biosentinel species that can be used to estimate MeHg contamination of waterbodies. In this study, I used long-jawed orb weavers (Tetragnatha sp.) as a biosentinel species to examine MeHg contamination along the Clear Fork and the West Fork of the Trinity River, Fort Worth, Texas. The objectives of this study were to: 1) evaluate MeHg contamination in long-jawed orb weavers from two forks of the Trinity River, and 2) determine if the concentrations of MeHg in the spiders pose a risk to songbirds that feed on spiders. I collected 101 and 105 spiders along the Clear Fork and the West Fork, respectively. I used a Direct Mercury Analyzer to determine the total Hg concentration of the long-jawed orb weavers. Because MeHg is the primary species of mercury in spider tissues, I used total Hg as a proxy for MeHg. All spiders were contaminated with MeHg, with spiders along the Clear Fork having significantly higher MeHg concentrations than spiders along the West Fork. Methylmercury in spiders increased with spider size along the Clear Fork. Concentrations of MeHg in spiders along the Clear Fork and the West Fork were high enough to pose a risk to the physiology of nestling songbirds that feed on spiders.

Methylmercury (MeHg) is an aquatic contaminant that can be transferred to terrestrial predators by emergent aquatic insects such as odonates (damselflies and dragonflies). We observed the effects of time on odonate-mediated MeHg flux (calculated as emergent odonate biomass MeHg concentration) in 20 experimental ponds and the potential risk to nestling red-winged blackbirds (Agelaius phoeniceus) posed by consuming MeHg-contaminated odonates. Emergent odonates were collected weekly from ponds containing four emergent traps per pond over an 9-mo period (February–October 2017). The MeHg flux from damselflies, aeshnid dragonflies, and libellulid dragonflies began in March and peaked in May, June, and July, respectively, and then declined throughout the rest of the summer. Nesting of red-winged blackbirds overlapped with peak odonate emergence and odonate-mediated MeHg flux. Because their diet can be dominated by damselflies and dragonflies, we tested the hypothesis that MeHg-contaminated odonates may pose a health risk to nestling red-winged blackbirds. Concentrations of MeHg in odonates exceeded wildlife values (the minimum odonate MeHg concentrations causing physiologically significant doses in consumers) for nestlings, suggesting that MeHg-contaminated odonates can pose a health risk to nestling red-winged blackbird.