Experimental increase in baseline corticosterone level reduces oxidative damage and enhances innate immune response

Authors marked in boldface are EvolEcol members.

Vágási CI, Pătraș L, Pap PL, Vincze O, Mureșan C, Németh J and Lendvai ÁZ 2018. Experimental increase in baseline corticosterone level reduces oxidative damage and enhances innate immune response. PLoS One 13: e0192701. URL


Glucocorticoid (GC) hormones are significant regulators of homeostasis. The physiological effects of GCs critically depend on the time of exposure (short vs. long) as well as on their circulating levels (baseline vs. stress-induced). Previous experiments, in which chronic and high elevation of GC levels was induced, indicate that GCs impair both the activity of the immune system and the oxidative balance. Nonetheless, our knowledge on how mildly elevated GC levels, a situation much more common in nature, might influence homeostasis is limited. Therefore, we studied whether an increase in GC level within the baseline range suppresses or enhances condition (body mass, hematocrit and coccidian infestation) and physiological state (humoral innate immune system activity and oxidative balance). We implanted captive house sparrows Passer domesticus with either 60 days release corticosterone (CORT) or control pellets. CORT-treated birds had elevated baseline CORT levels one week after the implantation, but following this CORT returned to its pre-treatment level and the experimental groups had similar CORT levels one and two months following the implantation. The mass of tail feathers grown during the initial phase of treatment was smaller in treated than in control birds. CORT implantation had a transient negative effect on body mass and hematocrit, but both of these traits resumed the pre-treatment values by one month post-treatment. CORT treatment lowered oxidative damage to lipids (malondialdehyde) and enhanced constitutive innate immunity at one week and one month post-implantation. Our findings suggest that a relatively short-term (i.e. few days) elevation of baseline CORT might have a positive and stimulatory effect on animal physiology.

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Oxidative physiology of reproduction in a passerine bird: a field experiment

This paper got accepted in Behavioural Ecology and Sociobiology.

Authors marked in boldface are EvolEcol members.

Pap PL, Vincze O, Fülöp A, Székely-Béres O*, Pătraș L, Pénzes J* and Vágási CI 2018. Oxidative physiology of reproduction in a passerine bird: a field experiment. Behavioural Ecology and Sociobiology (in press).


Organisms face resource trade-offs to support their parental effort and survival. The life history oxidative stress hypothesis predicts that an individual’s redox state modulates the trade-off between current and residual fitness, but this has seldom been tested experimentally in non-captive organisms. In this study, we manipulated the brood size in breeding pairs of barn swallows (Hirundo rustica) and found that females tending enlarged broods had increased levels of plasma oxidative damage (malondialdehyde concentration). This effect, however, was not accompanied by either a depletion, or defensive upregulation in antioxidants (glutathione, total antioxidant capacity and uric acid) that may explain the increase in oxidative damage. Brood size manipulation and the level of plasma oxidative damage during brood-rearing are not translated into decreased annual return rate, which does not support the oxidative stress hypothesis of life-history trade-offs. On the contrary, we found that female’s oxidative damage and total glutathione levels, an important intracellular non-enzymatic antioxidant measured at hatching decreased and correlated positively, respectively with annual return rate, suggesting that oxidative condition at hatching might be a more important contributor to fitness than the oxidative physiology measured during chick rearing. We also show that individual traits and ecological factors, such as the timing of breeding and the abundance of blood-sucking nest mites, correlated with the redox state of males and females during brood care.

Keywords: Antioxidants, Barn swallows, Life-history trade-offs, Lipid peroxidation, Oxidative stress, Parasitism

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Orsolya Vincze – researcher portrait

Orsolya Vincze was EvolEcol group member during her BSc and MSc at the Babeș-Bolyai University, Romania. Then she moved to the University of Debrecen, Hungary for her PhD, but all that time she continued to remain close to the EvolEcol group having significant contribution to many studies. Now close to her PhD defence, she came back to the EvolEcol group being employed as a full-time researcher in a national grant financed by the Romanian Ministry of Research.

Despite her young age and being at the beginning of her researcher career, Orsolya has many intriguing results published in high-ranking international journals, including a co-authored paper published in Nature. She was recently interviewed by Daniel David, the vice-rector of the Babeș-Bolyai University responsible for research, who asked her about what drove her towards biology, research and Babeș-Bolyai University, and what she is planning for the near future. The interview can be accessed here.


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Density-dependent sex ratio and sex-specific preference for host traits in parasitic bat flies

Authors marked in boldface are EvolEcol members.

Szentiványi T, Vincze O and Estók P 2017. Density-dependent sex ratio and sex-specific preference for host traits in parasitic bat flies. Parasites & Vectors 10: 405. pdf

DOI: 10.1186/s13071-017-2340-0



Deviation of sex ratios from unity in wild animal populations has recently been demonstrated to be far more prevalent than previously thought. Ectoparasites are prominent examples of this bias, given that their sex ratios vary from strongly female- to strongly male-biased both among hosts and at the metapopulation level. To date our knowledge is very limited on how and why these biased sex ratios develop. It was suggested that sex ratio and sex-specific aggregation of ectoparasites might be shaped by the ecology, behaviour and physiology of both hosts and their parasites. Here we investigate a highly specialised, hematophagous bat fly species with strong potential to move between hosts, arguably limited inbreeding effects, off-host developmental stages and extended parental care.


We collected a total of 796 Nycteribia kolenatii bat flies from 147 individual bats using fumigation and subsequently determined their sex. We report a balanced sex ratio at the metapopulation level and a highly variable sex ratio among infrapopulations ranging from 100% male to 100% female. We show that infrapopulation sex ratio is not random and is highly correlated with infrapopulation size. Sex ratio is highly male biased in small and highly female biased in large infrapopulations. We show that this pattern is most probably the result of sex-specific preference in bat flies for host traits, most likely combined with a higher mobility of males. We demonstrate that female bat flies exert a strong preference for high host body condition and female hosts, while the distribution of males is more even.


Our results suggest that locally biased sex ratios can develop due to sex-specific habitat preference of parasites. Moreover, it is apparent that the sex of both hosts and parasites need to be accounted for when a better understanding of host-parasite systems is targeted.

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New grant won & started

Our EvolEcol Group was recently financed by the Romanian Ministry of Research and Innovation for a grant entitled: Sex differences in life-history traits in birds and mammals: the significance of physiological state. The grant will run for 30 months. The main aim of the grant is to understand the physiological underpinnings of sexual differences in life histories among birds and mammals. Physiology will be characterized be immunological and oxidative physiological measures, and the level of insulin-like growth factor 1 (IGF-1). The grant involves 3 senior scientists (Péter L. Pap as PI, Orsolya Vincze and Csongor I. Vágási) and 1 MSc student (Janka Pénzes). For the IGF-1 level we collaborate with the group lead by Ádám Z. Lendvai at the University of Debrecen, Hungary. We post all the news related to this grant at this blog and our group’s twitter page.

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Paper on breeding effort, cohabitation with farm animals & feather-associated bacteria accepted in Journal of Avian Biology

Authors marked in boldface are EvolEcol members.

Fülöp A, Vágási CI and Pap PL 2017. Cohabitation with farm animals rather than breeding effort increases the infection with feather-associated bacteria in the barn swallow Hirundo rustica. Journal of Avian Biology (in press).

DOI: 10.1111/jav.01262

URL: http://www.avianbiology.org/accepted-article/cohabitation-farm-animals-rather-breeding-effort-increases-infection-feather

Abstract: Feather-associated bacteria are widespread inhabitants of avian plumage. However, the determinants of the between-individual variation in plumage bacterial loads are less well understood. Infection intensities can be determined by ecological factors, such as breeding habitat, and can be actively regulated by hosts via preening. Preening, yet, is a resource intensive activity, and thus might be traded-off against reproductive investment in breeding birds. Here, we studied barn swallows Hirundo rustica to assess the bacterial cost of reproduction in relation to nesting site micro-habitats. Barn swallows prefer to breed in the company of large-sized farm animals, although the presence of mammalian livestock in barns assures a warm and humid micro-climate that favours bacterial proliferation. Thus, we experimentally manipulated brood sizes of birds breeding in barns with, or without, farm animals and measured total cultivable bacteria (TCB) and feather-degrading bacteria (FDB) from the plumage. We found that the abundance of feather-associated bacteria (i.e. both TCB and FDB) in females, but not males, breeding in barns with livestock were significantly higher than in conspecifics breeding in empty barns. Plumage bacterial loads, however, were not affected by brood size manipulations in either sex. In addition, we report a negative relationship between both TCB and FDB and hatching date in females, and several sex and seasonal differences in plumage bacterial abundances. Our study is the first to show that breeding micro-habitat (i.e. livestock co-tenancy) has consequences for the abundance of feather-associated bacteria.


Image source: http://jeb.biologists.org/content/212/22/3621

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A phylogenetic comparative analysis reveals correlations between body feather structure and habitat

Our paper in Functional Ecology is now edited. http://onlinelibrary.wiley.com/wol1/doi/10.1111/1365-2435.12820/abstract


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