Offspring survival is negatively related to maternal response to sheep red blood cells in zebra finches

The immune system is an important player in individual trade-offs, but what has rarely been explored is how different strategies of investment in immune response may affect reproductive decisions. We examined the relationship between the strength of maternal immune response and offspring viability and immune response in captive zebra finches Taeniopygia guttata. In three independent experiments, the females and subsequently their adult offspring were challenged with sheep red blood cells, and their responses were measured. There was no relationship between offspring immune response and that of their mothers. However, we found offspring survival until adulthood to be negatively related to maternal antibody titers. That effect was consistent among all experiments and apparent despite the fact that we partially cross-fostered newly hatched nestlings between nests of different females. This suggests that the observed effects of maternal immune response is not mediated by potentially altered female rearing abilities. To our knowledge, this is the first study showing the relationship between the strength of the immune response and between-generational fitness costs in birds

Longitudinal studies confirm faster telomere erosion in short-lived bird species

Evidence is accumulating that telomeres become shorter with advancing age and possibly explain some of the observed variation in longevity. Cross-sectional analyses have shown that species with shorter lifespans lose more telomeric repeats with age than species with longer lifespans. Using existing data from longitudinal studies performed on several bird species, we confirmed a negative relationship between the rate of telomere shortening and maximum longevity

Benefits of extra-pair mating may depend on environmental conditions-anexperimental study in the blue tit (Cyanistes caeruleus)

Extra-pair mating constitutes a relatively common reproductive strategy in many socially monogamous bird species. This strategy may considerably improve reproductive success of males, but female benefits from extra-pair matings still remain unclear and empirical evidence is scarce. This may be because genetic benefits of extra-pair mating are not always revealed. It is possible that they are shown only in unfavourable environmental conditions and hence problems arise with detecting differences between within- and extra-pair offspring whose performance is measured under favourable conditions. In order to test this prediction, we manipulated environmental conditions by altering brood sizes of blue tits and compared phenotypic characteristics of within- and extra-pair offspring in mixed-paternity broods. We found that extra-pair young exhibited a higher response to phytohemagglutinin in comparison to within-pair young, but this was only observed among nestlings from experimentally enlarged broods. These results indicate that genetic benefits may interact with the environment, and thus benefits of extra-pair mating are likely to become visible only when conditions are relatively unfavourable

Utjecaj enzimske hidrolize na antioksidativna svojstva alkoholnih ekstrakata uljnih pogača

The aim of the present study is to compare changes in the total phenolic, flavonoid and reducing sugar content and antioxidant activity of alcoholic extracts of Oenothera biennis, Borago officinalis and Nigella sativa oilseed cakes before and after enzymatic hydrolysis. Extraction with ethanol and hydrolysis with different commercially available glycosidases: α-amylase, β-glucosidase, β-glucanase and their combinations in a ratio of 1:1:1 were investigated. Total phenolic, flavonoid and reducing sugar content, iron-chelating activity and antioxidant activity according to DPPH and ABTS tests were measured in non-hydrolysed extracts and compared with the results obtained for the extracts after the application of immobilised enzymes. As a result, the hydrolysed extracts had a higher phenolic and reducing sugar content as well as higher iron-chelating and antioxidant activities. Total phenolic content of Oenothera biennis, Borago officinalis and Nigella sativa oilseed cake extracts after enzymatic hydrolysis was higher in comparison with non-hydrolysed extracts, i.e. 2 times (for the enzyme combination), and 1.5 and 2 times (for β-glucanase) (p<0.05), respectively. The best results in increasing the flavonoid and sugar content as well as in iron-chelating activity were obtained after enzymatic hydrolysis of oilseed cake extracts by β-glucanase. Oilseed cake extracts after hydrolysis with an enzyme combination in a ratio of 1:1:1 had the highest increase in antioxidant activity.Svrha je ovoga rada bila odrediti utjecaj enzimske hidrolize na udjel ukupnih fenola, flavonoida i reducirajućih šećera, te na antioksidativnu aktivnost alkoholnih ekstrakata uljnih pogača noćurka (Oenothera biennis), boražine (Borago oficinalis) i crnog kima (Nigella sativa). Provedena je ekstrakcija pomoću etanola, te hidroliza pomoću različitih komercijalnih glikozidaza: α-amilaza, β-glukozidaza, β-glukanaza i njihove kombinacije u omjeru 1:1:1. U ekstraktima su uljnih pogača određeni sljedeći parametri: udjel ukupnih fenola, flavonoida i reducirajućih šećera, sposobnost stvaranja kelata i antioksidativna aktivnost ispitana pomoću DPPH i ABTS radikala, a rezultati su uspoređeni s onima dobivenim nakon hidrolize pomoću imobiliziranih enzima. Hidrolizirani su ekstrakti imali veći udjel viših fenola i reducirajućih šećera, te bolju sposobnost stvaranja kelata i veću antioksidativnu aktivnost od nehidroliziranih ekstrakata. Ukupni je udjel fenola u ekstraktu uljne pogače noćurka nakon hidrolize s kombinacijom enzima u omjeru 1:1:1 bio dva puta veći nego u nehidroliziranom ekstraktu, dok je primjenom β-glukanaze dobiven 1,5 puta veći udjel fenola u ekstraktu boražine, te 2 puta veći udjel fenola u ekstraktu crnog kima (p<0,05). Najveći udjeli flavonoida i reducirajućih šećera, te najveća sposobnost stvaranja kelata dobiveni su nakon enzimske hidrolize ekstrakata uljnih pogača s pomoću β-glukanaze. Ekstrakti su uljnih pogača imali najveću antioksidativnu aktivnost nakon hidrolize pomoću kombinacije enzima u omjeru 1:1:1

Determinants of prevalence and intensity of infection with malaria parasites in the Blue Tit

Parasite species are usually specialists utilising specific host species, but parasite assemblages may differ substantially even between populations of the same species and show seasonal and annual fluctuations. Host characteristics such as individual age and sex may also affect parasite species composition and abundance. Here, we report the occurrence of malaria parasites in the Blue Tit (Cyanistes caeruleus) inhabiting Gotland (Sweden) across 5 years. Using PCR-based techniques, we found eight cytochrome b lineages belonging to genus Plasmodium (pTURUD1, pBT7, pSGS1, pSW2, pGRW11) and Haemoproteus (hPARUS1, hPHSIB1, hWW2) with the overall prevalence of 65 %. The Plasmodium infections predominated (prevalence of 49.5 %), whereas Haemoproteus infection rate was much lower (prevalence of 16.5 %). We showed significant differences in infection status between study years and age classes when all parasite lineages were analysed together or the two most common lineages were analysed separately. Overall, older birds showed higher prevalence. A significant interaction between year and genus effect significantly explained variation in infection intensity. This interaction stems from a significant yearly variation of the infection intensity with Plasmodium, while such an effect is not present for Haemoproteus infections. More importantly, the intensity of infection with Haemoproteus was significantly higher than with Plasmodium in 3 out of the 4 study years with data

Sex‐specific heritability of cell‐mediated immune response in the blue tit nestlings (Cyanistes caeruleus)

Here, we aimed at estimating sex-specific heritabilities of cell-mediated immune response (CMI) in the blue tit nestlings (Cyanistes caeruleus). To separate genetic and environmental components of the phenotypic variance in CMI (measured using phytohaemagglutinin assay), we performed a cross-fostering experiment. Additionally, controlled environmental variation was introduced by enlarging some broods. Our analyses revealed a significant genetic component (as approximated by the nest-of-origin term) of the phenotypic variance in immune response. More importantly, these genetic effects differed between sexes and experimentally manipulated brood sizes, as indicated by significant genotype-by-sex and genotype-by-environment interactions. We discuss possible causes of such sexual dimorphism in gene expression and suggest that sex- and environment-specific genetic interactions may contribute to the maintenance of genetic variability in traits related to immune functions.</p

Experimentally increased reproductive effort alters telomere length in the blue tit (Cyanistes caeruleus)

Telomeres have recently been suggested to play important role in ageing and are considered to be a reliable ageing biomarkers. The life history theory predicts that costs of reproduction should be expressed in terms of accelerated senescence, and some empirical studies do confirm such presumption. Thus, a link between reproductive effort and telomere dynamics should be anticipated. Recent studies have indeed demonstrated that reproduction may trigger telomere loss, but actual impact of reproductive effort has not received adequate attention in experimental studies. Here, we experimentally manipulated reproductive effort by increasing the brood size in the wild blue tit (Cyanistes caeruleus). We show that parents attending enlarged broods experienced larger yearly telomere decay in comparison to control birds attending unaltered broods. In addition, we demonstrate that the change in telomere length differs between sexes, but this effect was independent from our treatment. To our knowledge, this is the first experimental study in the wild revealing that telomere dynamics may be linked to reproductive effort. Thus, telomere shortening may constitute one of the potential proximate mechanisms mediating the costs of reproduction.</p

The causes and consequences of inbreeding avoidance and tolerance in cooperatively breeding vertebrates

Cooperative breeders provide a particularly interesting scenario for studying inbreeding. Such populations are viscous due to delayed dispersal and short dispersal distances, resulting in the build-up of relatives in the local population. This leads to a high risk of inbreeding, and consequently of inbreeding depression. This has driven the evolution of an array of inbreeding avoidance mechanisms resulting in a relatively low level of close inbreeding in the majority of cooperative breeders. However, there are a number of species where inbreeding occurs relatively frequently. The presence of regular inbreeding (in cases where inbreeding is not a result of recent population declines), suggests that inbreeding tolerance and even preference can evolve under some circumstances. Both inbreeding and inbreeding avoidance mechanisms have enormous downstream fitness consequences for cooperative breeding species. For example, they can influence reproductive dynamics leading to a monopolisation of breeding opportunities by dominant individuals. Inbreeding and its avoidance are also likely to impact on the evolution of cooperative breeding itself through influencing levels of relatedness between potential cooperators. Finally, in some cooperative breeders, a high degree of inbreeding avoidance can be detrimental to population viability, and hence is of particular concern to conservationists. In this review, I discuss these issues in detail and also briefly consider recent advances in the methods available for the study of inbreeding in natural populations

Nosemosis negatively affects honeybee survival : experimental and meta-analytic evidence

Nosemosis, caused by microsporidian parasites of the genus Nosema, is considered a significant health concern for insect pollinators, including the economically important honeybee (Apis mellifera). Despite its acknowledged importance, the impact of this disease on honeybee survivorship remains unclear. Here, a standard laboratory cage trial was used to compare mortality rates between healthy and Nosema-infected honeybees. Additionally, a systematic review and meta-analysis of existing literature were conducted to explore how nosemosis contributes to increased mortality in honeybees tested under standard conditions. The review and meta-analysis included 50 studies that reported relevant experiments involving healthy and Nosema-infected individuals. Studies lacking survivorship curves or information on potential moderators, such as spore inoculation dose, age of inoculated bees, or factors that may impact energy expenditure, were excluded. Both the experimental results and meta-analysis revealed a consistent, robust effect of infection, indicating a threefold increase in mortality among the infected group of honeybee workers (hazard ratio for infected individuals = 3.16 [1.97–5.07] and 2.99 [2.36–3.79] in the experiment and meta-analysis, respectively). However, the meta-analysis also indicated high heterogeneity in the effect magnitude, which was not explained by our moderators. Furthermore, there was a serious risk of bias within studies and potential publication bias across studies. The findings underscore knowledge gaps in the literature. It is stressed that laboratory cage trials should be viewed as an initial step in evaluating the impact of Nosema on mortality and that complementary field and apiary studies are essential for identifying effective treatments to preserve honeybee populations

Extra-pair parentage and personality in a cooperatively breeding bird

Why so much variation in extra-pair parentage occurs within and among populations remains unclear. Often the fitness costs and benefits of extra-pair parentage are hypothesised to explain its occurrence; therefore, linking extra-pair parentage with traits such as personality (behavioural traits that can be heritable and affect reproductive behaviour) may help our understanding. Here, we investigate whether reproductive outcomes and success are associated with exploratory behaviour in a natural population of cooperatively breeding Seychelles warblers (Acrocephalus sechellensis) on Cousin Island. Exploratory behaviour correlates positively with traits such as risk-taking behaviour and activity in other wild bird species and might promote extra-pair mating by increasing the rate at which potential extra-pair partners are encountered. We therefore predicted that fast-exploring individuals would have more extra-pair offspring. There is also a potential trade-off between pursuing extra-pair parentage and mate guarding in males. We therefore also predicted that fast-exploring males would be more likely to pursue extra-pair parentage and that this would increase the propensity of their mate to gain extra-pair parentage. We found that neither the total number of offspring nor the number of extra-pair offspring were associated with a male’s or female’s exploratory behaviour. However, there was a small but significant propensity for females to have extra-pair fertilisations in pairs that were behaviourally disassortative. Overall, we conclude that, due to the small effect size, the association between exploratory behaviour and extra-pair paternity is unlikely to be biologically relevant. Significance statement: True genetic monogamy is rare, even in socially monogamous systems, and multiple factors, such as behaviour, social structure, morphology and physiology, determined by the biological system can cause variation in extra-pair parentage (EPP). Therefore, investigating the inherent differences in these factors among individuals could be informative. We investigated whether reproductive outcomes/success are associated with differences in the propensity to explore novel environments/objects in a promiscuous, island-dwelling cooperatively breeding bird, the Seychelles warbler. Our results showed that exploratory behaviour was not associated with the number of offspring produced by an individual, and thus the long-term fitness consequences of different exploratory tendencies did not differ. We also found that the propensity to engage in EPP in females was higher in dissimilar behavioural pairs, but due to the small effect size, we hesitate to conclude that there are personality-dependent mating outcomes in the population