Manrico Sebastiano, Marcel Eens, Simone Messina, Hamada AbdElgawad, Kévin Pineau, Gerrit T.S. Beemster, Olivier Chastel, David Costantini

Throughout their lives, all living organisms are potentially exposed to the action of pathogens. In most cases, these pathogens cause little or no damage to individuals or natural populations. However, when favourable conditions are created (e.g. environmental changes leading to a more rapid diffusion of the pathogen; deteriorated health status of living organisms), these pathogens can spread so rapidly that they cause episodes of mass mortality in natural populations.

During the breeding season, Magnificent frigatebird males show an inflated scarlet gular pouch to attract the female.
During the breeding season, Magnificent frigatebird males show an inflated scarlet gular pouch to attract the female.

In early life, living organisms can be more vulnerable as their immune systems and their biological defences are not yet fully developed and efficient. Here, we studied a population of Magnificent frigatebirds (Figure 1), a seabird of tropical and sub-tropical regions known for its capacity to steal food from other birds. The population is located off the coasts of French Guiana, and hosts approximately 1,300 reproductive pairs of frigatebirds whose chicks show clinical signs due to a disease that is causing the death of about 85-95% of chicks each year.

We have analysed the blood of both sick and healthy chicks, and we have found that sick chicks have impaired levels of antioxidants and high damage to biological molecules. For these reasons, we experimentally increased the dietary intake of resveratrol, a molecule with strong antioxidant and antiviral properties that is naturally abundant in peanuts and grapes.

The administration of this natural compound i) protected treated frigatebird chicks from the damage to some biological molecules caused by the disease ; ii) increased antioxidant levels; and iii) stimulated the production of some molecules involved in the immune response. Our work illustrates how the availability of specific organic molecules in the diet of free-living animals may constrain the individuals’ capacity to cope with viral infections.

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