High frequency of albinism and tumours in free-living birds around Chernobyl.

The effects of radioactive contamination on the phenotype of free-living organisms are poorly understood, mainly because of the difficulty of capturing the large numbers of individual specimens that are required to quantify rare events such as albinism and tumour formation. We hypothesized that the frequency of abnormalities like albinism and the frequency of radiation-induced diseases like cancer would increase with the level of background radiation, that the two markers of radiation would be positively correlated, and that the reduction in abundance of animals would be greater in species with a higher frequency of albinism and tumour formation, if these markers reliably reflected poor viability. Here we analyzed the frequency of albinistic feathers and tumours in a sample of 1669 birds captured during 2010-2012 at eight sites around Chernobyl that varied in level of background radiation from 0.02 to more than 200µSv/h. We recorded 111 cases of partial albinism and 25 cases of tumour formation. Nominal logistic models were used to partition the variance into components due to species and background radiation. Radiation was a strong predictor of the two markers in birds, with a small, but significant effect of species for albinism. The slope of the relationship between abundance and radiation in different bird species was significantly inversely correlated with the frequency of albinism and tumours, as was to be expected if a common underlying cause (i.e. radiation) affects both variables. These findings are consistent with the hypothesis that background radiation is a cause of albinism and tumours, that albinism and tumours are biomarkers of radiation exposure, and that high frequencies of albinism and tumours were present despite the low viability of birds with these conditions.

The role of gene flow asymmetry along an environmental gradient in constraining local adaptation and range expansion.

Theoretically, asymmetric gene flow along an environmental gradient can limit species range expansion by keeping peripheral populations from locally adapting. However, few empirical studies have examined this potentially fundamental evolutionary mechanism. We address this possibility in the cricket Allonemobius socius, which exist along a season-length gradient where the probability of producing a single generation per year (univoltinism) increases with latitude. As the probability of univoltinism increases northwards, populations are expected to hedge their bets by producing a greater proportion of diapause eggs when exposed to a mild diapause cue. However, gene flow from southern populations may disrupt local adaptation in the north by reducing the proportion of diapause eggs (expected to be 100% in pure univoltine environments). This may limit range expansion along the northern periphery where A. socius compete with A. fasciatus, a sister species that exhibits an invariant diapause-only egg-laying strategy. To assess the potential for range limitation, we examined diapause incidence (the proportion of diapause eggs produced under diapause conditions), gene flow symmetry and population structure across nine A. socius populations. We found that gene flow was asymmetric and biased northwards towards the periphery. Furthermore, peripheral populations that inhabited pure univoltine environments produced numerous nondiapause eggs (a southern, bivoltine diapause phenotype), which we assume to be a suboptimal phenotype. These patterns suggest that asymmetric gene flow along the gradient constrains adaptation in peripheral populations, potentially constraining species range expansion.

Effects of parental radiation exposure on developmental instability in grasshoppers.

Mutagenic and epigenetic effects of environmental stressors and their transgenerational consequences are of interest to evolutionary biologists because they can amplify natural genetic variation. We studied the effect of parental exposure to radioactive contamination on offspring development in lesser marsh grasshopper Chorthippus albomarginatus. We used a geometric morphometric approach to measure fluctuating asymmetry (FA), wing shape and wing size. We measured time to sexual maturity to check whether parental exposure to radiation influenced offspring developmental trajectory and tested effects of radiation on hatching success and parental fecundity. Wings were larger in early maturing individuals born to parents from high radiation sites compared to early maturing individuals from low radiation sites. As time to sexual maturity increased, wing size decreased but more sharply in individuals from high radiation sites. Radiation exposure did not significantly affect FA or shape in wings nor did it significantly affect hatching success and fecundity. Overall, parental radiation exposure can adversely affect offspring development and fitness depending on developmental trajectories although the cause of this effect remains unclear. We suggest more direct measures of fitness and the inclusion of replication in future studies to help further our understanding of the relationship between developmental instability, fitness and environmental stress.

DNA methylation in Drosophila melanogaster may depend on lineage heterogeneity.

DNA methylation has been discovered in Drosophila only recently. Current evidence indicates that de novo methylation patterns in drosophila are maintained in a different way compared to vertebrates and plants. As the genomic role and determinants of DNA methylation are poorly understood in invertebrates, its link with several factors has been suggested. In this study, we tested for the putative link between DNA methylation patterns in Drosophila melanogaster and radiation or the activity of P transposon. Neither of the links was apparent from the results, however, we obtained some hints on a possible link between DNA methylation pattern and genomic heterogeneity of fly lineages.

Determinants of age-dependent change in a secondary sexual character.

Many secondary sexual characters vary in a systematic way with the age of individuals, with young and old individuals displaying at lower levels than individuals of intermediate age. Analyses quantifying the within-individual and among-individual components of phenotypic variation can help partition effects of phenotypic plasticity and selective mortality. We analysed phenotypic variation in the expression of a secondary sexual character, tail length, in male and female barn swallows Hirundo rustica from four European populations studied during 11-26 years, using linear mixed effect models to describe age-related expression. Tail length increased from yearlings to intermediate aged birds with a subsequent decrease at old age. In males, this age-related pattern was because of both within-subject and between-subject effects, with no difference among populations. Males having longer lifespan had shorter tails when young than those having shorter lifespan. Females showed similar patterns of age-related variation as males, with no difference among populations. The major difference between sexes was that the between-subject effects (i.e. disappearance effects or selection) were much more important for males compared to females for which lifetime variation in tail length was mainly because of a within-subject effect (i.e., a plastic response). These findings suggest that whereas males trade greater expression of the secondary sexual character at young age against longevity, that was not the case for females. This is consistent with tail length being more costly in males than in females, with the cost of long tails potentially being offset by elevated mating success, whereas that is not the case in females.

Historical mutation rates predict susceptibility to radiation in Chernobyl birds.

Extreme environmental perturbations are rare, but may have important evolutionary consequences. Responses to current perturbations may provide important information about the ability of living organisms to cope with similar conditions in the evolutionary past. Radioactive contamination from Chernobyl constitutes one such extreme perturbation, with significant but highly variable impact on local population density and mutation rates of different species of animals and plants. We explicitly tested the hypothesis that species with strong impacts of radiation on abundance were those with high rates of historical mutation accumulation as reflected by cytochrome b mitochondrial DNA base-pair substitution rates during past environmental perturbations. Using a dataset of 32 species of birds, we show higher historical mitochondrial substitution rates in species with the strongest negative impact of local levels of radiation on local population density. These effects were robust to different estimates of impact of radiation on abundance, weighting of estimates of abundance by sample size, statistical control for similarity in the response among species because of common phylogenetic descent, and effects of population size and longevity. Therefore, species that respond strongly to the impact of radiation from Chernobyl are also the species that in the past have been most susceptible to factors that have caused high substitution rates in mitochondrial DNA.

[Association of P-mobile element activity and DNA methylation pattern changes in the conditions of Drosophila melanogaster prolonged irradiation].

Association of the radiosensitivity and epigenetic pattern DNA changes at the conditions of prolonged irradiation was investigated. Two laboratory Drosophila melanogaster strains (Canton-S and ri) irradiated for 20 generations to low doses rate (1.2 x 10(-1), 0.8 x 10(-8) and 0.12 x 10(-8) Gy/s) were used as experimental objects. DNA for the analysis was extracted separately for the flies of males and females. Restriction endonucleases Glul, Glal were used. Restriction analysis has shown that there are different DNA methylated patterns for males and females as for control and exposed variants. At the chronic irradiation there was the decline of methylation level at the enzymes Glul, Glal sites recognition.

[Dynamics of gonadal dysgenesis frequency in Drosophila melanogaster under controlled conditions of chronic radiation exposure].

Two Drosophila melanogaster strains (Canton-S and ri-lines) for 20 generations were in the controlled terms of chronic irradiation with 3-dose rate (1,2 x 10(-8); 0,3 x 10(-8); 0,12 x 10(-8) Gy/c). The dynamics of hybrid dysgenesis frequency was explored for each generation of F1 descendants from Canton-S and ri-lines crossing. The gradual change of dose response of hybrid dispense depending on duration of irradiation of ancestors and dose rate was shown. The complex dynamics of hybrid dysgenesis frequency depending on irradiation duration of ancestors and dose rate was detected. The cumulative effect of the prolonged irradiation shows up as adaptation at the lowest dose rate and as exhaustion at the highest dose rate. Question comes into discussion about the features of transitional process and including of protective and adaptive reactions hierarchy at the conditions of radiation factor chronic action.

[Changes in wheat DNA methylation pattern after chronic seed gamma-irradiation].

Alterations of DNA methylation patterns of wheat two varieties--Odessa' albatross and Donetsk 48 have been studied. Seeds were irradiated for 4 months with low dose rate (3 x 10(-7) Gy/s). Six restriction endonucleases were used in the experiments. Primary distinction in DNA methylation patterns of the studied varieties has been demonstrated. The chronic irradiation resulted in the increase of methylation level on the sites of recognition for Glul and Sou3Al and in the decline of this index for the sites of recognition of GlaI and HpaII. The meaningful increase of chromosome aberration levels was demonstrated at the same accumulated dose of chronic irradiation. The role of changes of DNA methylation patterns in development of radiation damage and organism protective reactions is discussed.

Senescent sperm performance in old male birds.

Senescence is the deterioration of the phenotype with age caused by negative effects of mutations acting late in life or the physiological deterioration of vital processes. Birds have traditionally been assumed to senescence slowly despite their high metabolic rates, high blood sugar levels and high body temperature. Here we investigate the patterns of age-related performance of sperm of a long distance migrant, the barn swallow Hirundo rustica, varying in age from 1 to 6 years, analysed by the computer-assisted sperm analysis equipment. Sperm showed deteriorating performance in terms of linear movement, track velocity, straight line velocity and reduced proportions of rapidly moving, progressive and motile sperm with age. In a second series of experiments, we assessed performance of sperm from the same males in neutral medium and in medium derived from the reproductive tract of females in an attempt to test if sperm of old males performed relatively better in female medium, as expected from extra-pair paternity being negatively related to male age, but not to female age. Older males showed consistently better performance in female medium than in neutral medium in terms of track velocity, straight line velocity and reduced proportions of rapidly moving, progressive and motile sperm, whereas young males showed better performance in neutral medium. These results provide evidence of declining sperm performance for important reproductive variables not only with age, but also with the sperm of old males performing differentially better in female medium than young males.

[The dynamics of P-mobile Drosophila melanogaster element activation in controlled terms of protracted irradiation].

Verification of hypothesis about mobile element activation radiosensitivity change in the conditions of the prolonged irradiation was the research goal. The estimation of orientation of these changes depending on the accumulated dose and their characteristic times were conducted. Two Drosophila melanogaster strains (Canton-S and P-lines) for 20 generations were in the controlled terms of chronic irradiation with 3-dose rate (1.2 x 10(-8), 0.6 x 10(-8) and 0.12 x 10(-8) Gy/c). The dynamics of hybrid dysgenese frequency was explored for each generation of F1 descendants from Canton-S and P-lines crossing. The gradual change of dose response of hybrid disgenesis depending on duration of irradiation of ancestors and dose rate was shown. The complex dynamics of hybrid dysgenese frequency depending on irradiation duration of ancestors and dose rate was shown. The cumulative effect of the prolonged irradiation shows up as adaptation at the lowest dose rate and as exhaustion at the highest dose rate. Question comes into discussion about the features of transitional process and including of protective and adaptive reactions hierarchy at the conditions of radiation factor chronic action.

Impaired swimming behaviour and morphology of sperm from barn swallows Hirundo rustica in Chernobyl.

We investigated the motility and morphology of live sperm from barn swallows Hirundo rustica breeding in radioactively contaminated areas around Chernobyl and control areas in Ukraine in order to test the hypothesis that swimming behaviour and morphology of sperm was impaired by radioactive contamination. We obtained sperm samples from 98% of sampled birds, thus avoiding sampling bias due to the fraction of males not producing sperm samples. Analyses of within- and between-sample repeatability revealed significant and intermediate to large estimates for all sperm parameters. There were significant differences between the Chernobyl area and the control area for two of 11 sperm behaviour parameters, and significant interactions between area and year for six of these parameters. The proportion of sperm with abnormal morphology was elevated in barn swallows from Chernobyl. A principal component (PC) analysis revealed four significant axes that explained 88% of the variance in sperm behaviour parameters. One of these principal components differed between areas, and three components showed significant year by area interactions. PC2 representing the frequency of slow sperm increased with increasing radiation in one year, but not another. PC3 representing sperm with high linearity, small amplitude of lateral head displacement and low track velocity decreased with increasing background radiation level. PC4 reflecting a large proportion of static sperm with high beat cross frequency increased with increasing background radiation level. Sperm behaviour as reflected by principal components was predictable among years from information on level of radiation, and it was predictable among sites in different years. These results are consistent with the hypothesis that sperm behaviour and morphology have been affected by radiation due to the Chernobyl accident.

[The features of radioactive contamination of small birds in Chernobyl zone in 2003-2005].

Radioactive contamination of small birds (484 individuals, 44 species) was investigated in the Chernobyl zone (Ukraine) in 2003-2005. Values variation of 90Sr and of 137Cs activity concentration reached 3-4 orders of magnitude even in one site, and maximum values amounted to hundreds Bq/g at the central plots of the zone. The biggest contamination is appropriate to birds in breeding season and to settled species, whilst migrants are the "cleanest". Change of contamination within a year reflects seasonal and short-term changes in birds diet and in behaviour. During breeding season females have higher activity concentration of 90Sr, while on 137Cs accumulation sexual differences are absent. In other seasons radioactive contamination of male and female does not differ if they live in similar conditions and have similar migratory behavior. Young birds during fledging and just after, as a rule, have higher levels of 90Sr contamination than adults, and actually do not differ on 137Cs accumulation. On a set of own and published data, it was assumed, that in small birds the half-life period of 137Cs extraction amounts to 1-2 days, and 90Sr- 5-10 days, and dynamic equilibrium of the radionuclides turnover in organism is reached over 4-7 and 17-34 days, respectively, after the birds arrival on the contaminated site. Among 44 studied species, those who search invertebrates in soil top layer or forest litter (thrushes). have noticeably higher accumulation of 90Sr and of 137Cs. Specific differences of radionuclides accumulation for the rest birds were not revealed due to small sample sizes of the species.

Reduced colonization by soil invertebrates to irradiated decomposing wood in Chernobyl.

Soil is inhabited by a range of microbes, invertebrates and vertebrates that disintegrate and decompose dead wood and leaf litter. These communities can be perturbed by ionizing radiation from natural radiation sources or from radiation originating from nuclear accidents such as those at Chernobyl, Fukushima and Three Mile Island. We used experimental manipulations of wood quality due to differences in exposure to ionizing radiation among tree trunks and ambient radiation levels of the soil to test the hypothesis that radioactively contaminated wood would result in a negative correlation between the abundance of soil invertebrates colonizing slices of wood and level of radioactive contamination. We extracted soil invertebrates underneath decomposing wood using mustard powder diluted in water. The abundance of soil invertebrates extracted was highly repeatable at study sites and decreased with increasing ambient radiation and total dose measured with thermoluminescent dosimeters (TLDs). Four 10 cm thick slices of ca. 70-year old Scots pines (Pinus sylvestris) were deposited at 20 sites and the invertebrate taxa and their colonization and their abundance was assessed annually during 2014-2017. There were more soil invertebrates under uncontaminated than contaminated slices of wood. In addition, there were more soil invertebrates in areas with less ambient radioactivity, and there was an interaction effect between contamination of wood and ambient radiation implying that the role of contamination differed among slices. Finally, there was an increase in the abundance of soil invertebrates under wood slices during 2013-2017 implying that the abundance of soil invertebrates increased over time. These findings imply that the abundance of soil animals colonizing wood slices was dependent on background radiation, radioactive contamination of wood and the interaction between contamination of wood and ambient radiation.

Birds prefer to breed in sites with low radioactivity in Chernobyl.

Low-level radioactive contamination may affect choice of breeding site and life-history decisions if (i) radioactivity directly affects body condition or (ii) it affects resource abundance that then secondarily influences reproductive decisions. We tested the effects of radioactive contamination on nest-site choice and reproduction in a community of hole nesting birds by putting up nest boxes in areas differing in levels of background radiation. Great tit Parus major and pied flycatcher Ficedula hypoleuca significantly avoided nest boxes in heavily contaminated areas, with a stronger effect in flycatchers than in tits. These preferences could not be attributed to variation in habitat quality or resource abundance, as determined by analyses of habitat use and the relationship between radiation and life-history characters. Likewise, none of these effects could be attributed to individuals of a specific age breeding in the most contaminated areas. Laying date and clutch size were not significantly related to dose rate in either species. Hatching success was depressed by elevated radioactive contamination, interacting with habitat in the great tit and with laying date in the pied flycatcher. Interspecific differences in effects of radiation on nest-site choice suggest that species respond in a species-specific manner to radiation, perhaps related to differences in migratory habits. We suggest that individual body condition rather than secondary effects of radiation on resource abundance account for the effects on nest box use and hatching success.

Chernobyl as a population sink for barn swallows: tracking dispersal using stable-isotope profiles.

Stable-isotope profiles of feathers can reveal the location or habitat used by individual birds during the molting period. Heterogeneity in isotope profiles will reflect heterogeneity in molt locations, but also heterogeneity in breeding locations, because spatial heterogeneity in molt locations will be congruent with spatial heterogeneity in breeding locations in species with high connectivity between breeding and molting sites. We used information on the congruence of spatial heterogeneity in molt and breeding location to study population processes in Barn Swallows (Hirundo rustica) from a region. near Chernobyl, Ukraine, that has been radioactively contaminated since 1986; from an uncontaminated control region near Kanev, Ukraine; and from a sample of pre-1986 museum specimens used to investigate patterns prior to the nuclear disaster at Chernobyl, from both regions. Previous studies have revealed severe reductions in Barn Swallow reproductive performance and adult survival in the Chernobyl region, implying that the population is a sink and unable to sustain itself. Female Barn Swallows are known to disperse farther from their natal site than males, implying that female stable-isotope profiles should tend to be more variable than profiles of males. However, if the Barn Swallows breeding at Chernobyl are not self-sustaining, we would expect males there also to originate from a larger area than males from the control region. We found evidence that the sample of adult Barn Swallows from the Chernobyl region was more isotopically heterogeneous than the control sample, as evidenced from a significant correlation between feather sigma13C and sigma15N values in the control region, but not in the Chernobyl region. Furthermore, we found a significant difference in feather sigma15N values between regions and periods (before and after 1986). When we compared the variances in sigma13C values of feathers, we found that variances in both sexes from post-1986 samples from Chernobyl were significantly larger than variances for feather samples from the control region, and than variances for historical samples from both regions. These findings suggest that stable-isotope measurements can provide information about population processes following environmental perturbations.

Ionizing radiation, antioxidant response and oxidative damage: A meta-analysis.

One mechanism proposed as a link between exposure to ionizing radiation and detrimental effects on organisms is oxidative damage. To test this hypothesis, we surveyed the scientific literature on the effects of chronic low-dose ionizing radiation (LDIR) on antioxidant responses and oxidative damage. We found 40 publications and 212 effect sizes for antioxidant responses and 288 effect sizes for effects of oxidative damage. We performed a meta-analysis of signed and unsigned effect sizes. We found large unsigned effects for both categories (0.918 for oxidative damage; 0.973 for antioxidant response). Mean signed effect size weighted by sample size was 0.276 for oxidative damage and -0.350 for antioxidant defenses, with significant heterogeneity among effects for both categories, implying that ionizing radiation caused small to intermediate increases in oxidative damage and small to intermediate decreases in antioxidant defenses. Our estimates are robust, as shown by very high fail-safe numbers. Species, biological matrix (tissue, blood, sperm) and age predicted the magnitude of effects for oxidative damage as well as antioxidant response. Meta-regression models showed that effect sizes for oxidative damage varied among species and age classes, while effect sizes for antioxidant responses varied among species and biological matrices. Our results are consistent with the description of mechanisms underlying pathological effects of chronic exposure to LDIR. Our results also highlight the importance of resistance to oxidative stress as one possible mechanism associated with variation in species responses to LDIR-contaminated areas.

Resuspension and atmospheric transport of radionuclides due to wildfires near the Chernobyl Nuclear Power Plant in 2015: An impact assessment.

In April and August 2015, two major fires in the Chernobyl Exclusion Zone (CEZ) caused concerns about the secondary radioactive contamination that might have spread over Europe. The present paper assessed, for the first time, the impact of these fires over Europe. About 10.9 TBq of (137)Cs, 1.5 TBq of (90)Sr, 7.8 GBq of (238)Pu, 6.3 GBq of (239)Pu, 9.4 GBq of (240)Pu and 29.7 GBq of (241)Am were released from both fire events corresponding to a serious event. The more labile elements escaped easier from the CEZ, whereas the larger refractory particles were removed more efficiently from the atmosphere mainly affecting the CEZ and its vicinity. During the spring 2015 fires, about 93% of the labile and 97% of the refractory particles ended in Eastern European countries. Similarly, during the summer 2015 fires, about 75% of the labile and 59% of the refractory radionuclides were exported from the CEZ with the majority depositing in Belarus and Russia. Effective doses were above 1 mSv y(-1) in the CEZ, but much lower in the rest of Europe contributing an additional dose to the Eastern European population, which is far below a dose from a medical X-ray.

Antioxidants, radiation and mutation as revealed by sperm abnormality in barn swallows from Chernobyl.

Reduced levels of antioxidants such as carotenoids and vitamins A and E can increase DNA damage caused by free radicals. Exposure to radiation has been proposed to reduce levels of antioxidants that are used for DNA repair and this reduction may be responsible for increased levels of mutation in radioactively contaminated areas. We test this hypothesis using field measures of antioxidants in blood, liver and eggs of the barn swallow Hirundo rustica while relating these to levels of mutation as reflected by the frequency of abnormal sperm. Antioxidant levels in blood, liver and eggs were reduced in Chernobyl, Ukraine, compared with an uncontaminated control area, and levels of antioxidants correlated negatively with levels of background radiation. The frequency of abnormal sperm was almost an order of magnitude higher in Chernobyl than in the control area and was negatively related to antioxidant levels in blood and liver. This is consistent with the hypothesis of a direct link between radiation and individual levels of antioxidants, suggesting that levels of mutation differ among individuals owing to individual differences in the abundance of antioxidants.

Abundance and genetic damage of barn swallows from Fukushima.

A number of studies have assessed or modeled the distribution of the radionuclides released by the accident at the Fukushima-Daiichi Nuclear Power Plant (FDNPP). Few studies however have investigated its consequences for the local biota. We tested whether exposure of barn swallow (Hirundo rustica) nestlings to low dose ionizing radiation increased genetic damage to their peripheral erythrocytes. We estimated external radiation exposure by using thermoluminescent dosimeters, and by measuring radioactivity of the nest material. We then assessed DNA damage by means of the neutral comet assay. In addition, we conducted standard point-count censuses of barn swallows across environmental radiation levels, and estimated their abundance and local age ratio. Radioactivity of nest samples was in the range 479-143,349 Bq kg(-1), while external exposure varied between 0.15 and 4.9 mGy. Exposure to radioactive contamination did not correlate with higher genetic damage in nestlings. However, at higher levels of radioactive contamination the number of barn swallows declined and the fraction of juveniles decreased, indicating lower survival and lower reproduction and/or fledging rate. Thus, genetic damage to nestlings does not explain the decline of barn swallows in contaminated areas, and a proximate mechanism for the demographic effects documented here remains to be clarified.