Sex-biased terminal investment in offspring induced by maternal immune challenge in the house wren ( Troglodytes aedon )

Abstract

The reproductive costs associated with the upregulation of immunity have been well-documented and constitute a fundamental trade-off between reproduction and self-maintenance. However, recent experimental work suggests that parents may increase their reproductive effort following immunostimulation as a form of terminal parental investment as prospects for future reproduction decline. We tested the trade-off and terminal investment hypotheses in a wild population of house wrens (Troglodytes aedon) by challenging the immune system of breeding females with lipopolysaccharide, a potent but nonlethal antigen. Immunized females showed no evidence of reproductive costs; 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 exhibited higher cutaneous immune responsiveness to phytohaemagglutinin injection, constituting an adaptive strategy of sex-biased allocation by immune-challenged females to enhance the reproductive value of their offspring. Thus, our results are consistent with the terminal investment hypothesis, and suggest that maternal immunization can induce pronounced transgenerational effects on offspring phenotypes.

Condition-dependent sex difference in nestling House Wren (Troglodytes aedon) response to phytohaemagglutinin injection

“…Given the myriad of factors potentially affecting immune responsiveness, it is not surprising that some studies have detected sexual dimorphism in the response of altricial nestlings to the injection of phytohemagglutinin (PHA) (Fargallo et al 2002;Tschirren et al 2003;Chin et al 2005;Bize et al 2005;Dubiec et al 2006;Bowers et al 2012), whereas others have not (Saino et al 2002;Dubiec and Cichoń 2005;Wilk et al 2007;Arriero 2009). Such decidedly mixed results may reflect differences in the nature and extent of natural immune challenges between species and even populations.…”

“…Alternatively, the immune system of male and female nestlings might develop differently in the common nest environment if selection favors either allocating different levels of resources to developing structures and systems, such as the immune system, in the two sexes (Dubiec et al 2006;van der Most et al 2011) or differential priming in ovo of the nestling immune system (e.g., Grindstaff et al 2006). Under some circumstances, as for example when males as adults must compete intensely for access to resources or mates, selection may favor male nestlings that maximize their size, stamina, and strength at the expense of the development of their immunity, while selection may favor females that do the opposite (Bowers et al 2012). …”

Post-hatch heat warms adult beaks: irreversible physiological plasticity in Japanese quail

“…We initially included all two-way interaction terms, which if non-significant ( p . 0.10, following the study of Bowers et al [35]) were deleted from models and the analysis was re-run. The interaction between age and experimental treatment was of interest a priori and was always retained in the model.…”

Female pipefish can detect the immune status of their mates

“…Mate choice favoring individuals with immune experience may also pay off as previous parasitic experience could result in increased investment into reproduction, since the likelihood to survive and reproduce in the future is decreased (terminal investment theory: Clutton-Brock 1984;Simmons 1994;Bonneaud et al 2004). We thus predict that, paradoxically, the choosing sex may select immunechallenged individuals and that such preference may enhance offspring fitness due to the production of more viable offspring with a stronger immune response (Pfennig and Tinsley 2002;Bowers et al 2012).…”