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.

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.

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.