Michelle L. Beck

Interspecific differences in egg production affect egg trace element concentrations after a coal fly ash spill.

In oviparous vertebrates, trace elements transfer from mother to offspring during egg production. For animals that produce eggs slowly, like turtles, the trace element concentration of each egg reflects an integration of dietary and stored accumulation over the duration of vitellogenesis. Because turtles also produce eggs synchronously, all eggs within a clutch should exhibit uniform trace element concentrations. In contrast, for animals that produce eggs in sequence and primarily from current dietary resources, like many birds, the trace element concentrations of eggs should be less uniform within a clutch, and likely reflect short-term changes in dietary exposure. We tested the hypothesis that stinkpot turtle (Sternotherus odoratus) clutches exhibit lower variability and higher repeatability in barium, selenium, strontium, and thallium concentrations than those of tree swallows (Tachycineta bicolor) from a site impacted by a recent coal ash spill. All four trace elements exhibited significantly lower variability and significantly higher repeatability in stinkpot clutches than in swallow clutches. Mean trace element concentrations of stinkpot eggs were also significantly higher than those of swallow eggs although both species feed primarily on aquatic invertebrates. Variability in swallow egg trace element concentrations was partially due to significant laying order effects. Our results support the hypothesis that interspecific variation in the source of resources and in the synchronicity and rate of egg production can lead to interspecific differences in the variability of egg trace element concentrations.

Exposure to residual concentrations of elements from a remediated coal fly ash spill does not adversely influence stress and immune responses of nestling tree swallows

We examined the effects of elements from a remediated fly ash spill on nestling tree swallow physiology. Nestlings were exposed to modestly elevated concentrations of elements including selenium near the spill. Bacteria killing capacity was positively related to selenium exposure, but element exposure was unrelated to other aspects of physiology.

Haematological and immunological characteristics of eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) infected and co-infected with endo- and ectoparasites

Disease is among the leading causes of global amphibian population declines, and may contribute to declines of the giant hellbender salamander (Cryptobranchus alleganiensis). We provide some of the first information about how hellbenders physiologically respond to end- and ecto- parasites, insights that could be critical to their conservation.

Repeatability and sources of variation of the bacteria-killing assay in the common snapping turtle

Abstract Research on reptile ecoimmunology lags behind that on other vertebrates, despite the importance of such studies for conservation and evolution. Because the innate immune system is highly conserved across vertebrate lineages, assessments of its performance may be particularly useful in reptiles. The bacteria‐killing assay requires a single, small blood sample and quantifies an individuals ability to kill microorganisms. The assays construct validity and interpretability make it an attractive measure of innate immunity, but it requires proper optimization and sample storage. We optimized this assay for the common snapping turtle (Chelydra serpentina) to assess the repeatability of the assay and the effects of freezing and thawing on bactericidal capacity. We determined whether age (adult female and hatchlings) or incubation temperature influenced bactericidal capacity. We found that the assay was repeatable and that freezing plasma samples for 6 weeks at −80°C did not decrease bactericidal capacity nor did a single 30‐min thaw and subsequent refreezing. However, we detected subtle interassay variation and results from one assay were 5–6% greater than those from the other two. Adult females had significantly greater bactericidal ability than hatchlings and we found no relationship between incubation temperature and bactericidal capacity. This assay is a useful tool in snapping turtles and may have applicability in other reptiles. However, species‐specific optimization is required to ensure that variation among individuals exceeds interassay variation. Consideration should be given to optimization conditions that facilitate comparisons between or within groups, particularly groups that differ considerably in bactericidal capacity. GRAPHICAL ABSTRACT Bactericidal capacity of plasma from common snapping turtles frozen at −80°C does not degrade over 6 weeks. However, the assay must be optimized properly to ensure that variation among individuals exceeds interassay variation. Figure. No caption available.

Beeswax corticosterone implants produce long-term elevation of plasma corticosterone and influence condition

Glucocorticoids can play a critical role in modulating life-history trade-offs. However, studying the effects of glucocorticoids on life-history often requires experimentally elevating plasma glucocorticoid concentrations for several weeks within normal physiological limits and without repeated handling of the animal. Recently, implants made of beeswax and testosterone (T) were shown to have release dynamics superior to some currently available T implants, and these beeswax implants dissolved, eliminating the need to recapture the animal. We evaluated the utility of beeswax implants containing four different dosages of corticosterone (CORT; the primary glucocorticoid in birds) and their effect on several condition indices in a captive colony of zebra finches (Taeniopygia guttata). The three implants with the greatest CORT doses (0.05, 0.1, and 0.5mg) produced spikes in plasma CORT concentrations 20h after treatment, but were within the limits that zebra finches may normally experience. The 0.5mg CORT implant elevated plasma CORT between typical baseline and restraint stress levels reported in other studies of zebra finches for the entire 35day experiment. Birds in the 0.5mg implant group were heavier, had greater furcular fat scores, and had lower hematocrit than birds in the control and other CORT implant groups. Beeswax CORT implants are a low cost method of elevating plasma CORT for a prolonged time. Furthermore, because there is no need to remove these implants at the end of a study, this method may be amenable to studies of free-ranging animals.

Variation in riparian consumer diet composition and differential bioaccumulation by prey influence the risk of exposure to elements from a recently remediated fly ash spill

Emerging aquatic insects play a key role in transporting aquatic nutrients and contaminants to riparian consumers. However, little is known about how within- and between-year variation in the diet or patterns of element bioaccumulation in emerging insect taxa may influence the risk of exposure to wildlife. During 2 breeding seasons, the composition of the diet of tree swallows (Tachycineta bicolor) was examined at several colonies that were exposed to element contamination from a remediated coal fly ash spill to determine how variation in the diet influenced the risk of exposure to elements. The proportion of the diet that consisted of insects with an aquatic larval stage was positively related to concentrations of As, Fe, Se, and Tl in the samples. The proportion of the diet that consisted of Chironomidae (midges) was positively related to exposure to these elements at most colonies within and between years. Ephemeroptera (mayflies) contained higher concentrations of Se than midges, including 17 samples with concentrations of Se above 5 µg/g dry mass, the threshold of toxicological concern for birds. This was even the case at colonies several kilometers downstream from the spill. The results indicate that greater consideration should be given to the pattern of element bioaccumulation among different prey taxa and their relative importance in the diet to better assess the risk of contaminant exposure.

Relationships among plumage coloration, blood selenium concentrations and immune responses of adult and nestling tree swallows.

ABSTRACT In a number of taxa, males and females both display ornaments that may be associated with individual quality and could be reliable signals to potential mates or rivals. We examined the iridescent blue/green back and white breast of adult tree swallows (Tachycineta bicolor) to determine whether plumage reflectance is related to adult or offspring immune responses. We simultaneously addressed the influence of blood selenium levels and the interaction between blood selenium and plumage coloration on adult and nestling immunity. Selenium is a well-known antioxidant necessary for mounting a robust immune response but its importance in wild birds remains poorly understood. In females, the brightness of white breast coloration was positively associated with bactericidal capacity, but there was no association with blood selenium. In contrast, male bactericidal capacity was associated with an interactive effect between dorsal plumage coloration and blood selenium concentration. Males with bluer hues and greater blue chroma showed increased bactericidal capacity as blood selenium concentrations increased, while bactericidal capacity declined in greener males at higher blood selenium concentrations. In nestlings, bactericidal capacity was positively associated with nestling blood selenium concentrations and white brightness of both social parents. These results suggest that white plumage reflectance is indicative of quality in tree swallows and that greater attention should be paid to the reflectance of large white plumage patches. Additionally, the role of micronutrients, such as selenium, in mediating relationships between physiology and signals of quality, should be explored further. Summary: Selenium, an important micronutrient whose influence on the physiology of wild birds is poorly understood, and structural plumage coloration are related to innate immunity in adult and nestling tree swallows.

Urbanization alters the relationship between coloration and territorial aggression, but not hormones, in song sparrows

Melanin-based coloration is associated with aspects of phenotype, including conspecific aggression and hormone concentrations. These relationships could arise as a result of genetic and/or biochemical links between melanin production and other traits. Additionally, anthropogenic change, including urbanization, exposes animals to novel conditions that can alter pigmentation, behaviour or hormones, potentially disrupting relationships between coloration and other traits. We examined relationships among the extent and darkness of melanin spotting on the breast of male song sparrows, Melospiza melodia, territorial behaviour, plasma testosterone and corticosterone concentrations to determine whether coloration was reliably associated with phenotype in this species. We conducted this study in urban and rural populations to determine whether relationships between coloration, behaviour and hormones varied between habitats. Males in urban habitat had more extensive brown spotting than rural males. The relationship between melanin coloration and territoriality differed in urban and rural habitats. In rural sparrows, territoriality was negatively correlated with spotting area, while in urban sparrows territoriality was positively associated with spotting darkness. Regardless of habitat, males with more extensive spotting increased testosterone secretion more in response to gonadotropin-releasing hormone administration and males with darker spotting had greater handling restraint-induced release of corticosterone. This suggests that plumage coloration is associated with underlying physiology, but the relationship between coloration and behaviour may shift between habitats.