Paper on parasitism-linked physiological annual cycle accepted

In a previous paper we found that the cycling of host’s immune and oxidative physiological state over the annual cycle is largely unrelated to infestation by coccidians. In this study we used captive house sparrows that were either kept infested or were cured by oral administration of an anti-coccidial drug. Because physiological state might be altered due to captivity conditions, in an upcoming study we reconsidered whether coccidians do influence the seasonal fluctuations in host physiology by sampling free-living house sparrows. Our new results basically concordant with what we have shown in the lab: coccidians have little effect on the on the seasonal changes in physiological traits. These new results were now conditionally accepted for publication in Physiological and Biochemical Zoology. Authors marked by boldface are EvolEcol members.

Pap PL, Pătraș L, Osváth G, Buehler DM, Versteegh MA, Sesarman A, Banciu M and Vágási CI 2015. Seasonal patterns and relationships among coccidian infestations, measures of oxidative physiology, and immune function in free-living house sparrows over an annual cycle. Physiological and Biochemical Zoology (in press).

Abstract: Temporal variation in oxidative physiology and its associated immune function may occur as a result of changes in parasite infection over the year. Evidence from field and laboratory studies suggests links between infection risk, oxidative stress, and the ability of animals to mount an immune response; however the importance of parasites in mediating seasonal change in physiological make-up is still debated. Also, we know almost nothing about the temporal consistency of relationships among parasite infestation, markers of oxidative status and immune function in wild animals, and whether variation in oxidative measures can be viewed as a single integrated system. To address these questions, we sampled free-living house sparrows (Passer domesticus) every two months over a complete year and measured infestation with coccidian parasites, as well as 9 traits that reflect condition, oxidative physiology and immune function. We found significant seasonal variation coccidian infestation and in 7 out of 9 condition and physiological variables over the year. However, we found little support for parasite-mediated change in condition, oxidative physiology and immune functions in house sparrows. In accordance with this, we found no temporal consistency in relationships between the intensity of infestation and physiology. Among measures of oxidative physiology, antioxidants (measured as the total antioxidant capacity and the concentration of uric acids in the plasma) and oxidative damage (measured through the level of malondialdehyde in plasma) positively and consistently covaried over the year, while no such associations were found for the rest of traits (body mass, total glutathione and leukocyte numbers). Our results show that natural levels of chronic coccidian infection have limited effect on the seasonal change of physiological traits, suggesting that the variation of the latter are probably more affected by short term disturbances, such as acute infection and/or season-specific stress stimuli.

Key words: birds, heterophil to lymphocyte ratio, leukocyte count, oxidative state, parasites, seasonality

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