22.3 Friday, Jan. 4 Immune challenge and terminal investment in female house wrens (Troglodytes aedon) BOWERS, E.K.*; SAKALUK, S.K.; THOMPSON, C.F.; Illinois St. Univ. firstname.lastname@example.org
The reproductive costs associated with up-regulation of the immune system have been well-documented and arise from a trade-off between reproductive effort and self-maintenance. However, some recent studies that activated the immune system of breeding individuals found that parents actually increased, rather than decreased, reproductive effort following immunostimulation, suggesting terminal parental investment as prospects for future reproduction declined. We tested the trade-off and terminal investment hypotheses in a free-living population of house wrens (Troglodytes aedon) by challenging the immune system of breeding females with an antigen, lipopolysaccharide. Immunized females showed no evidence of subsequent reproductive costs associated with the immunostimulation; instead, they produced offspring of higher phenotypic quality, but in a sex-specific manner. Relative to control offspring, sons of immunized females had increased body mass and their sisters enhanced cutaneous immune responsiveness to phytohaemagglutinin injection. Further study suggests that immunostimulation leads to an increase in both pre-hatching resource allocation to eggs and post-hatching maternal effort when provisioning live young.