title: Immunocompetence of breeding females is sensitive to cortisol levels but not to communal rearing in the degu (Octodon degus).
abstract: One hypothesis largely examined in social insects is that cooperation in the context of breeding benefits individuals through decreasing the burden of immunocompetence and provide passive immunity through social contact. Similarly, communal rearing in social mammals may benefit adult female members of social groups by reducing the cost of immunocompetence, and through the transfer of immunological compounds during allonursing. Yet, these benefits may come at a cost to breeders in terms of a need to increase investment in individual immunocompetence. We examined how these potential immunocompetence costs and benefits relate to reproductive success and survival in a natural population of the communally rearing rodent, Octodon degus. We related immunocompetence (based on ratios of white blood cell counts, total and specific immunoglobulins of G isotype titers) and fecal glucocorticoid metabolite (FGC) levels of adults immunized with hemocyanin from the mollusk Concholepas concholepas to measures of sociality (group size) and communal rearing (number of breeding females). Offspring immunocompetence was quantified based on circulating levels of the same immune parameters. Neither female nor offspring immunocompetence was influenced by communal rearing or sociality. These findings did not support that communal rearing and sociality enhance the ability of females to respond to immunological challenges during lactation, or contribute to enhance offspring condition (based on immunocompetence) or early survival (i.e., to 3months of age). Instead, levels of humoral and cellular components of immunocompetence were associated with variation in glucorcorticoid levels of females. We hypothesize that this covariation is driven by physiological (life-history) adjustments needed to sustain breeding.
authors.affiliation: Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile. Electronic address: lebensperger@bio.puc.cl.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Ebensperger
authors.affiliation: Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile.
authors.forename: Cecilia
authors.initials: C
authors.lastname: León
authors.affiliation: Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile.
authors.forename: Juan
authors.initials: J
authors.lastname: Ramírez-Estrada
authors.affiliation: Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile; Instituto de Ecología y Biodiversidad (IEB), Las Palmeras 3425, Ñuñoa, Santiago, Chile.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Abades
authors.affiliation: Department of Biological and Environmental Sciences, University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA.
authors.forename: Loren D
authors.initials: LD
authors.lastname: Hayes
authors.affiliation: Fundación Ciencia y Tecnología para el Desarrollo (FUCITED), Santiago, Chile.
authors.forename: Esteban
authors.initials: E
authors.lastname: Nova
authors.affiliation: Fundación Ciencia y Tecnología para el Desarrollo (FUCITED), Santiago, Chile.
authors.forename: Fabián
authors.initials: F
authors.lastname: Salazar
authors.affiliation: Department of Biology, University of Louisiana, Monroe, LA 71209, USA.
authors.forename: Joydeep
authors.initials: J
authors.lastname: Bhattacharjee
authors.affiliation: Fundación Ciencia y Tecnología para el Desarrollo (FUCITED), Santiago, Chile; Biosonda Corporation, Santiago, Chile.
authors.forename: María Inés
authors.initials: MI
authors.lastname: Becker
mesh_terms: D000818:Animals; D001947:Breeding; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism*; D007121:Immunocompetence; D007074:Immunoglobulin G / Q000097:blood; D008214:Lymphocytes / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D009504:Neutrophils; D046329:Octodon / Q000097:blood* / Q000276:immunology*; D025341:Principal Component Analysis; D012919:Social Behavior
chemical_list: D005938:Glucocorticoids; D007074:Immunoglobulin G
keywords: Communal rearing; Concholepas hemocyanin; Cortisol; Direct fitness; Immunocompetence; Octodon degus; Social immunity; Sociality