Not just fuel: energy stores are correlated with immune function and oxidative damage in a long-distance migrant

In many animals,catabolic and anabolic periods are temporally separated.Migratory birds alternate energy expenditure during flight with energy accumulation during stopover.The size of the energy stores at stopover affects the decision to resume migration and thus the temporal organization of migration.We now provide data suggesting that it is not only the size of the energy stores per se that may influence migration scheduling,but also the physiological consequences of flying.In two subspecies of the northern wheatear Oenanthe oenanthe,a long-distance migrant,estimated energy stores at a stopover during autumn migration were positively related with both constitutive innate and acquired immune function,and negatively related with oxidative damage to lipids.In other words,migrants'physiological condition was associated with their energetic condition.Although time spent at stopover before sampling may have contributed to this relationship,our results suggest that migrants have to trade-off the depletion of energy stores during flight with incurring physiological costs.This will affect migrants'decisions when to start and when to terminate a migratory flight.The physiological costs associated with the depletion of energy stores may also help explaining why migrants often arrive at and depart from stopover sites with larger energy stores than expected.We propose that studies on the role of energy stores as drivers of the temporal organization of(avian)migration need to consider physiological condition,such as immunological and oxidative states.

Oxidative stress physiology in relation to life history traits of a free-living vertebrate:the spotted snow skink,Niveoscincus ocellatus

Recent research suggests that oxidative stress,via its links to metabolism and senescence,is a key mechanism linking life history traits such as fecundity and growth with survival;however,this has rarely been put under empirical scrutiny within free-living populations.Using a wild population of live-bearing skinks,we explored how plasma antioxidant activity(OXY),reactive oxidative metabolites(ROM),and the estimated oxidative stress index are associated with female and male life history.We found that male skinks have a significantly higher ROM and estimated oxidative stress index than female skinks,but this was not accompanied by a sex difference in mortality.Both sexes showed a non-linear association between OXY and age,indicating that the oldest and youngest individuals had the lowest OXY.Interestingly,female skinks with high OXY showed a decreased probability of survival to the following season.However,we found no significant associations between female reproductive investment(litter size or litter mass)or parturition date(i.e.metabolism)and oxidative status.Combined,our results offer mixed support for a role of oxidative stress in mediating life history traits and suggest that future studies need to explore oxidative stress during vitellogenesis in addition to using an intra-individual approach to understand the cost of reproduction and patterns of aging.

Corrigendum to: Not just fuel: energy stores are correlated with immune function and oxidative damage in a long-distance migrant

Current Zoology 2019 doi:10.1093/cz/zoz009 Advance Access Publication Date:7 March 2019.