Sex-Related Effects of an Immune Challenge on Growth and Begging Behavior of Barn Swallow Nestlings

Abstract

Parent-offspring conflicts lead the offspring to evolve reliable signals of individual quality, including parasite burden, which may allow parents to adaptively modulate investment in the progeny. Sex-related variation in offspring reproductive value, however, may entail differential investment in sons and daughters. Here, we experimentally manipulated offspring condition in the barn swallow (Hirundo rustica) by subjecting nestlings to an immune challenge (injection with bacterial lipopolysaccharide, LPS) that simulates a bacterial infection, and assessed the effects on growth, feather quality, expression of morphological (gape coloration) and behavioral (posture) begging displays involved in parent-offspring communication, as well as on food allocation by parents. Compared to sham-injected controls, LPS-treated chicks suffered a depression of body mass and a reduction of palate color saturation. In addition, LPS treatment resulted in lower feather quality, with an increase in the occurrence of fault bars on wing feathers. The color of beak flanges, feather growth and the intensity of postural begging were affected by LPS treatment only in females, suggesting that chicks of either sex are differently susceptible to the immune challenge. However, irrespective of the effects of LPS, parents equally allocated food among control and challenged offspring both under normal food provisioning and after a short period of food deprivation of the chicks. These results indicate that bacterial infection and the associated immune response entail different costs to offspring of either sex, but a decrease in nestling conditions does not affect parental care allocation, possibly because the barn swallow adopts a brood-survival strategy. Finally, we showed that physiological stress induced by pathogens impairs plumage quality, a previously neglected major negative impact of bacterial infection which could severely affect fitness, particularly among long-distance migratory birds.

Fault bars in bird feathers: mechanisms, and ecological and evolutionary causes and consequences

“…A study by Romano et al (2011) is possibly the most interesting. They treated nestling barn swallows with bacterial lipopolysaccharide (LPS), thus simulating a bacterial infection without the detrimental costs of actual infections and found both the prevalence and abundance of fault bars to be about twice as high in experimental than in control nestlings.…”

Leptin, a neuroendocrine mediator of immune responses, inflammation, and sickness behaviors

“…For example, animals stimulated with an immune challenge while engaging in reproduction and rearing of offspring often show reduced reproductive success (Bonneaud et al, 2003;Ilmonen et al, 2000;Uller et al, 2006). Similarly, animals that are mounting an immune response may show reduced growth and development (Fair et al, 1999;Romano et al, 2011).…”

Specific and non-overlapping functions of testosterone and 11-ketotestosterone in the regulation of professional phagocyte responses in the teleost fish gilthead seabream

“…Differences between the immune function of males and females have frequently been reported in mammals (Cohn, 1979;Bouman et al, 2005) and, more recently, in avian (Romano et al, 2011), reptile (Svensson et al, 2009) and fish (Hoeger et al, 2005). In mammals, females generate higher levels of antibodies in response to exogenous antigens (Adori et al, 2010;Friedman, 2010;Yeh and Chen, 2010) and show a lower incidence of tumors and better resistance against viral and parasitic infections (Filipin Mdel et al, 2010;Gillgrass et al, 2010), although this is accompanied by a greater susceptibility to developing autoimmune syndromes (Fairweather et al, 2008;Lee and Chiang, 2012).…”