Offspring innate immunity varies with parental age in a long-lived seabird

Parental age at reproduction is increasingly recognized as a factor influencing offspring lifespan and other fitness-related traits, yet the underlying proximate physiological mechanisms remain poorly understood. Immune function and oxidative status are two potential mediators of age-related parental effects, as both are key hallmarks of ageing. However, very few studies have examined the relationship between parental age and offspring physiological condition in wild populations. We examined immunological and cellular mechanisms potentially responsible for parental age effects in the long-lived seabird Scopoli's shearwater (Calonectris diomedea). We measured 10 markers of immune function and oxidative status in 35 chicks from either younger or older parents at two different developmental phases: one month of age and at fledging. Chicks of younger parents exhibited higher haptoglobin levels at fledging compared to chicks of older parents. No effects of parental age were found on leukocyte profiles, humoral components of acquired immunity, antioxidant enzyme activity, or DNA damage in the offspring. Our results suggest, whilst chicks of younger parents might experience more stressful conditions, overall mechanisms supporting somatic maintenance might shield offsprings from the transgenerational transfer of molecular damage that parents accumulate with age. Our findings provide novel insights into the physiological bases of parental age effects in a long-lived species.