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.

Alzheimer’s Disease (AD) is a neurodegenerative disease that is characterized by deficits in learning and memory. AD pathology is associated with neuronal death through the accumulation of amyloid beta (Aβ) plaques in the synapses. Our lab has previously demonstrated that Lipopolysaccharide (LPS), a component of gram-negative bacteria, induces an inflammatory response that increases Aβ found in the brain. Dendritic spines are projections on dendrites that may or may not be synapsing with an axon. Previous research indicates that there is a correlation between the number of properly functioning synapses and the number of dendritic spines. In this study, LPS was administered to induce inflammation, stimulating Aβ production. We then quantified dendritic spine density in order to compare dendritic spine density in the hippocampus of both LPS- and saline-treated groups. Contrary to our hypothesis, we saw a non-significant increase in dendritic spine density following LPS treatment, when compared to saline controls.

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.