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Body size and circulating levels of different molecules from tree swallows (Tachycineta bicolor) exposed to different doses of lipopolysaccharide (LPS)

Citation

Butler, Michael (2021), Body size and circulating levels of different molecules from tree swallows (Tachycineta bicolor) exposed to different doses of lipopolysaccharide (LPS), Dryad, Dataset, https://doi.org/10.5061/dryad.1vhhmgqt8

Abstract

The purpose of mounting an immune response is to destroy pathogens, but this response comes at a physiological cost, including the generation of oxidative damage. However, many studies on the effects of immune challenges employ a single high dose, meaning that the consequences of more mild immune challenges are poorly resolved. We tested whether the degree of immunological challenge in tree swallows (Tachycineta bicolor) affects oxidative physiology and body mass, and whether these metrics correlate with parasitic nest mite load. We injected 14-day-old nestlings with either 0, 0.01, 0.1, or 1 mg lipopolysaccharide (LPS) per kg body mass, then collected a blood sample 24-h later to quantify multiple physiological metrics, including oxidative damage (i.e., d-ROMs), circulating amounts of triglyceride and glycerol, and levels of the acute phase protein haptoglobin. After fledging, we identified and counted parasitic nest mites (Dermanyssus spp. and Ornithonyssus spp.). We found that only nestlings injected with 1 mg LPS/kg body mass, which is a common dosage in ecoimmunological studies, lost more body mass than individuals from other treatment groups. However, every dose of LPS resulted in a commensurate increase in oxidative damage. Parasitic mite abundance had no effect on oxidative damage across treatments. Amount of oxidative damage correlated with haptoglobin levels, suggesting compensatory mechanisms to limit self-damage during an immune response. We conclude that while only the highest-intensity immune challenges resulted in costs related to body mass, even low-intensity immune challenges result in detectable increases of oxidative damage.

Methods

Field- and lab-based data. Stored in Excel. Analyzed in SAS.