Browsing by Author "Beck, Michelle L."
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- Exposure to residual concentrations of elements from a remediated coal fly ash spill does not adversely influence stress and immune responses of nestling tree swallowsBeck, Michelle L.; Hopkins, William A.; Hallagan, John J.; Jackson, Brian P.; Hawley, Dana M. (Oxford University Press, 2014)Anthropogenic activities often produce pollutants that can affect the physiology, growth and reproductive success of wildlife. Many metals and trace elements play important roles in physiological processes, and exposure to even moderately elevated concentrations of essential and non-essential elements could have subtle effects on physiology, particularly during development. We examined the effects of exposure to a number of elements from a coal fly ash spill that occurred in December 2008 and has since been remediated on the stress and immune responses of nestling tree swallows. We found that nestlings at the site of the spill had significantly greater blood concentrations of Cu, Hg, Se and Zn in 2011, but greater concentrations only of Se in 2012, in comparison to reference colonies. The concentrations of elements were below levels of significant toxicological concern in both years. In 2011, we found no relationship between exposure to elements associated with the spill and basal or stress-induced corticosterone concentrations in nestlings. In 2012, we found that Se exposure was not associated with cellmediated immunity based on the response to phytohaemagglutinin injection. However, the bactericidal capacity of nestling plasma had a positive but weak association with blood Se concentrations, and this association was stronger at the spill site. Our results indicate that exposure to these low concentrations of elements had few effects on nestling endocrine and immune physiology. The long-term health consequences of low-level exposure to elements and of exposure to greater element concentrations in avian species require additional study.
- Haematological and immunological characteristics of eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) infected and co-infected with endo- and ectoparasitesHopkins, William A.; Fallon, Jesse A.; Beck, Michelle L.; Coe, Brittney H.; Jachowski, Catherine M.B. (Oxford University Press, 2016)Disease is among the leading causes of the global decline in amphibian populations. In North America, parasites and pathogens are among the factors implicated in precipitous population declines of the giant hellbender salamander (Cryptobranchus alleganiensis), but the incidence of infections and the responses of hellbenders to infections remain poorly studied. Here, we document the prevalence of leech and trypanosome infections in a wild population of eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) and describe haematological and immunological characteristics of hellbenders harbouring these infections. We hypothesized that hellbenders parasitized by trypanosomes would be anaemic, that individuals infected with either or both parasites would exhibit shifts in white blood cell counts and that hellbenders infected with leeches would exhibit altered plasma bactericidal capacity. We found that 24 and 68% of hellbenders in our sample population were infected with leeches and trypanosomes, respectively, and 20% were co-infected with both parasites. We found no evidence suggestive of anaemia among infected individuals. However, hellbenders infected with either or both parasites exhibited marked shifts in circulating white blood cells that were consistent with predictable responses to parasitic infection. Additionally, we found that hellbenders harbouring leeches had much higher plasma bactericidal capacity than individuals without leeches, and we offer multiple potential mechanistic explanations for this observation. We also found evidence that cellular and serological immune responses to parasites were less robust in juvenile than adult hellbenders. This finding warrants further investigation in light of the demographic characteristics, specifically the scarcity of juvenile age classes, of hellbender populations where disease is a possible contributor to declines. Finally, we describe two methodological advances that will improve future studies seeking to diagnose trypanosome infections and to test the bactericidal capacity of hellbenders and perhaps other amphibians. Our study provides fundamental insights into how hellbenders respond physiologically to endo- and ectoparasites, which could ultimately prove useful for their conservation.
- Male zebra finches exposed to lead (Pb) during development have reduced volume of song nuclei, altered sexual traits, and received less attention from females as adultsGoodchild, Christopher G.; Beck, Michelle L.; VanDiest, Issac; Czesak, Frankie N.; Lane, Samuel J.; Sewall, Kendra B. (Elsevier, 2021-01-08)Lead (Pb) is a pervasive global contaminant that interferes with sensitive windows for neurological development and causes oxidative damage to tissues. The effects of moderate and high exposure to Pb have been well-studied in birds, but whether low-level early-life exposure to Pb influences adult phenotype remains unclear. Female songbirds use a male’s song and coloration to discriminate between high- and low-quality males. Therefore, if early-life exposure to Pb disrupts song learning ability or shifts the allocation of antioxidant pigments away from colorful secondary sexual traits, male birds exposed to Pb may be less attractive to females. We exposed developing zebra finches (Taeniopygia guttata) to Pb-contaminated drinking water (100 or 1000 parts per billion [ppb]) after hatching (days 0–100). Once male finches reached adulthood (120–150 days post hatch), we measured song learning ability, coloration of bill and cheek patches, and volume of song nuclei in the brain. We also measured female preference for Pb-exposed males relative to control males. Finally, we measured motoric and spatial cognitive performance in male and female finches to assess whether cognitive traits differed in their sensitivity to Pb exposure. Male zebra finches exposed to 1000 ppb Pb had impaired song learning ability, reduced volume of song nuclei, bills with less redness and received less attention from females. Additionally, Pb exposure impaired motoric performance in both male and female finches but did not affect performance in a spatial cognitive task. Adult finches exposed to Pb-contaminated water had higher blood-Pb levels, though in all cases blood-Pb levels were below 7.0 μg dL⁻¹. This study suggests that low-level exposure to Pb contributes to cognitive deficits that persist into adulthood and may indirectly influence fitness by altering secondary sexual traits and reducing male attractiveness.