Limited Access to Food and Physiological Trade‐Offs in a Long‐Distance Migrant Shorebird. II. Constitutive Immune Function and the Acute‐Phase Response

Abstract

In response to unbalanced energy budgets, animals must allocate resources among competing physiological systems to maximize fitness. Constraints can be imposed on energy availability or energy expenditure, and adjustments can be made via changes in metabolism or trade-offs with competing demands such as body-mass maintenance and immune function. This study investigates changes in constitutive immune function and the acute-phase response in shorebirds (red knots) faced with limited access time to food. We separated birds into two experimental groups receiving either 6 h or 22 h of food access and measured constitutive immune function. After 3 wk, we induced an acute-phase response, and after 1 wk of recovery, we switched the groups to the opposite food treatment and measured constitutive immune function again. We found little effect of food treatment on constitutive immune function, which suggests that even under resource limitation, a baseline level of immune function is maintained. However, birds enduring limited access to food suppressed aspects of the acutephase response (decreased feeding and mass loss) to maintain energy intake, and they downregulated thermoregulatory adjustments to food treatment to maintain body temperature during simulated infection. Thus, under resource-limited conditions, birds save energy on the most costly aspects of immune defense.

Effects of early developmental conditions on innate immunity are only evident under favourable adult conditions in zebra finches

“…Bourgeon et al 2010;Buehler et al 2009b;Mauck et al 2005;Parejo et al 2007). The fact that agglutination titres did not vary with the experimental treatments in our study suggests that NAbs are not (or only slightly) affected by environmental conditions in zebra finches or that the species actively buffers NAbs against stress-induced changes (see also Buehler et al 2009a), possibly at the expense of investment in other life-history traits. Further experimental study is needed to discriminate between both hypotheses.…”

“…Likewise, NAb concentrations did not vary with clutch size or food limitation in several bird species (e.g. Buehler et al 2009a;Lee et al 2008), but significant relationships have been found with growth rate, mass differences among nestlings, prolonged fasting, body mass and environmental conditions in other species (e.g. Bourgeon et al 2010;Buehler et al 2009b;Mauck et al 2005;Parejo et al 2007).…”

Relationships between metabolic status, corticosterone secretion and maintenance of innate and adaptive humoral immunities in fasted re-fed mallards

“…response) in red knots (Calidris canutus) subjected to food shortages (Buehler et al, 2009). Likewise, Bourgeon and colleagues (Bourgeon et al, 2007a) showed in female common eiders (Somateria mollissima) that the induced innate immune response was maintained throughout the incubation fast while both cellular and humoral acquired components were negatively affected.…”

Reconfiguration of the immune system network during food limitation in the caterpillarManduca sexta

“…Both vertebrates and invertebrates have examples of constitutive and inducible responses (SchmidHempel, 2011). Which type of response requires the most resources depends on pathogen prevalence (Westra et al, 2015), although specific, inducible responses are thought to be less costly overall because of reduced running costs (Lee, 2006, but see Buehler et al, 2009). Finally, our assessment of the M. sexta immune system includes host resistance tests using three types of pathogen.…”