title: Relationships between host body condition and immunocompetence, not host sex, best predict parasite burden in a bat-helminth system.
abstract: Sex-biased parasitism highlights potentially divergent approaches to parasite resistance resulting in differing energetic trade-offs for males and females; however, trade-offs between immunity and self-maintenance could also depend on host body condition. We investigated these relationships in the big brown bat, Eptesicus fuscus, to determine if host sex or body condition better predicted parasite resistance, if testosterone levels predicted male parasite burdens, and if immune parameters could predict male testosterone levels. We found that male and female hosts had similar parasite burdens and female bats scored higher than males in only one immunological measure. Top models of helminth burden revealed interactions between body condition index and agglutination score as well as between agglutination score and host sex. Additionally, the strength of the relationships between sex, agglutination, and helminth burden is affected by body condition. Models of male parasite burden provided no support for testosterone predicting helminthiasis. Models that best predicted testosterone levels did not include parasite burden but instead consistently included month of capture and agglutination score. Thus, in our system, body condition was a more important predictor of immunity and worm burden than host sex.
authors.affiliation: Department of Biological Sciences, Western Michigan University, 1903 West Michigan Avenue, Kalamazoo, MI, 49008-5410, USA. elizabeth.m.warburton@wmich.edu.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Warburton
authors.affiliation: Department of Biological Sciences, Western Michigan University, 1903 West Michigan Avenue, Kalamazoo, MI, 49008-5410, USA.|Present address: Department of Biomedical Sciences, Grand Valley State University, 1 Campus Drive, Allendale, MI, 49401, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Pearl
authors.affiliation: Department of Biological Sciences, Western Michigan University, 1903 West Michigan Avenue, Kalamazoo, MI, 49008-5410, USA.|Environmental and Sustainability Studies Program, Western Michigan University, 1903 West Michigan Avenue, Kalamazoo, MI, 49008-5410, USA.
authors.forename: Maarten J
authors.initials: MJ
authors.lastname: Vonhof
mesh_terms: D000818:Animals; D002685:Chiroptera / Q000276:immunology / Q000469:parasitology* / Q000502:physiology; D005260:Female; D006374:Helminthiasis, Animal / Q000276:immunology* / Q000503:physiopathology; D006376:Helminths / Q000276:immunology / Q000502:physiology*; D006790:Host-Parasite Interactions; D007121:Immunocompetence; D008297:Male; D008954:Models, Biological; D012737:Sex Factors; D013739:Testosterone / Q000032:analysis
chemical_list: D013739:Testosterone
keywords: Body condition; Eptesicus fuscus; Helminthiasis; Immunocompetence; Sex-biased parasitism