High levels of fluctuating asymmetry in populations of Apodemus flavicollis from the most contaminated areas in Chornobyl

Fluctuating Asymmetry as a Measure of Stress in Natural Populations of Woody Plants: Influence of Ecological and Geographical Factors on Developmental Stability

Fluctuating asymmetry is a sensitive indicator of favorable conditions during the period of individual development. The influence of climatic factors, biotopic conditions, latitude, altitude, and age of plants from the natural populations of the silver birch Betula pendula Roth was analyzed. The material consisted of 13,000 leaves of the silver birch from 11 regions of north-eastern Siberia. The influence of 23 climatic factors and six integrated coefficients characterizing the general suitability of the climate, as well as summer, winter, spring, and autumn was analyzed. The developmental stability of woody plants and, consequently, the level of the FA of the lamina in natural biotopes can vary in a wide range. We found that climatic factors, mainly conditions in the warm season, have a significant impact. We also noted the influence of the age, biotope, and light conditions. For Betula pendula, an increase in FA was registered on the ecological periphery of its range, i.e., on the edge of the forest belt in the north and in the mountains. The data obtained demonstrate the high influence of natural stress-inducing factors on development stability in plants.

Radiocaesium accumulation and fluctuating asymmetry in the Japanese mitten crab, Eriocheir japonica, along a gradient of radionuclide contamination at Fukushima

The 2011 Tohoku earthquake-tsunami and the subsequent nuclear accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS) led to large-scale radionuclide contamination of the marine and freshwater environment. Monitoring studies of marine food products in the Fukushima region have generally demonstrated a declining trend in radiocaesium concentrations. However, the accumulation and elimination of radiocaesium and potential biological effects remain poorly understood for freshwater biota inhabiting highly contaminated areas at Fukushima. Consequently, the present study aimed to assess radiocaesium accumulation and developmental effects on the commercially important catadromous Japanese mitten crab, Eriocheir japonica. E. japonica were collected from four sites along a gradient of radionuclide contamination 4-44 km in distance from the FDNPS in 2017. To determine potential developmental effects, fluctuating asymmetry (FA) was used as a measure of developmental stability. Combined ¹³⁴Cs and ¹³⁷Cs values for whole E. japonica from highly contaminated sites 4 and 16 km in distance from the FDNPS were 3040 ± 521 and 2250 ± 908 Bq kg^-1 wet weight respectively, 30 and 22 times greater than the Japanese standard limit of 100 Bq kg^-1. Estimated total dose rates based on radiocaesium concentrations in whole crabs and sediment ranged from 0.016 to 37.7 μGy h^-1. No significant relationship between radiocaesium accumulation and FA was recorded, suggesting that chronic radiation exposure at Fukushima is not inducing developmental effects in E. japonica as measured using fluctuating asymmetry. Furthermore, estimated dose rates were below proposed regulatory limits where significant deleterious effects are expected. The present study will aid in the understanding of the long-term consequences of radiation exposure for non-human biota and the management of radioactively contaminated environments.

Canalization and developmental stability of the yellow-necked mouse (Apodemus flavicollis) mandible and cranium related to age and nematode parasitism

BACKGROUND

Mammalian mandible and cranium are well-established model systems for studying canalization and developmental stability (DS) as two elements of developmental homeostasis. Nematode infections are usually acquired in early life and increase in intensity with age, while canalization and DS of rodent skulls could vary through late postnatal ontogeny. We aimed to estimate magnitudes and describe patterns of mandibular and cranial canalization and DS related to age and parasite intensity (diversity) in adult yellow-necked mice (Apodemus flavicollis).

RESULTS

We found the absence of age-related changes in the levels of canalization for mandibular and cranial size and DS for mandibular size. However, individual measures of mandibular and cranial shape variance increased, while individual measures of mandibular shape fluctuating asymmetry (FA) decreased with age. We detected mandibular and cranial shape changes during postnatal ontogeny, but revealed no age-related dynamics of their covariance structure among and within individuals. Categories regarding parasitism differed in the level of canalization for cranial size and the level of DS for cranial shape. We observed differences in age-related dynamics of the level of canalization between non-parasitized and parasitized animals, as well as between yellow-necked mice parasitized by different number of nematode species. Likewise, individual measures of mandibular and cranial shape FA decreased with age for the mandible in the less parasitized category and increased for the cranium in the most parasitized category.

CONCLUSIONS

Our age-related results partly agree with previous findings. However, no rodent study so far has explored age-related changes in the magnitude of FA for mandibular size or mandibular and cranial FA covariance structure. This is the first study dealing with the nematode parasitism-related canalization and DS in rodents. We showed that nematode parasitism does not affect mandibular and cranial shape variation and covariance structure among and within individuals. However, parasite intensity (diversity) is related to ontogenetic dynamics of the levels of canalization and DS. Overall, additional studies on animals from natural populations are required before drawing some general conclusions.

A New Integrated Tool to Calculate and Map Bilateral Asymmetry on Three-Dimensional Digital Models

The observation and the quantification of asymmetry in biological structures are deeply investigated in geometric morphometrics. Patterns of asymmetry were explored in both living and fossil species. In living organisms, levels of directional and fluctuating asymmetry are informative about developmental processes and health status of the individuals. Paleontologists are primarily interested in asymmetric features introduced by the taphonomic process, as they may significantly alter the original shape of the biological remains, hampering the interpretation of morphological features which may have profound evolutionary significance. Here, we provide a new R tool that produces the numerical quantification of fluctuating and directional asymmetry and charts asymmetry directly on the specimens under study, allowing the visual inspection of the asymmetry pattern. We tested this show.asymmetry algorithm, written in the R language, on fossil and living cranial remains of the genus Homo. show.asymmetry proved successful in discriminating levels of asymmetry among sexes in Homo sapiens, to tell apart fossil from living Homo skulls, to map effectively taphonomic distortion directly on the fossil skulls, and to provide evidence that digital restoration obliterates natural asymmetry to unnaturally low levels.

Does stress mess with rodents' heads? Influence of habitat amount and genetic factors in mandible fluctuating asymmetry in South American water rats (Nectomys squamipes, Sigmodontinae) from Brazilian Atlantic rainforest remnants

Loss of developmental stability can lead to deviations from bilateral symmetry (i.e. Fluctuating Asymmetry - FA), and is thought to be caused by environmental and genetic factors associated with habitat loss and stress. Therefore, levels of FA might be a valuable tool to monitor wild populations if FA serves as an indicator of exposure to stress due to impacts of habitat loss and fragmentation. In studies examining FA and habitat fragmentation, FA levels are often explained by loss of genetic variation, though few studies have addressed FA's use as indicator of environmental impact. Here, we investigated whether habitat loss, genetic variation, and/or inbreeding affect the developmental instability in Brazilian Atlantic forest populations of a Neotropical water rat (Nectomys squamipes). We sampled individuals from eight sites within Atlantic forest remnants with different amounts of available forest habitat and assessed FA levels with geometric morphometric techniques using adult mandibles. We used observed heterozygosity (Ho) and inbreeding coefficient (Fis), from seven microsatellite markers, as a proxy of genetic variation at individual and population levels. Populations were not significantly different for shape or size FA levels. Furthermore, interindividual variation in both shape and size FA levels and interpopulational differences in size FA levels were best explained by chance. However, habitat amount was negatively associated with both interpopulational variance and average shape FA levels. This association was stronger in populations living in areas with <28% of forest cover, which presented higher variance and higher average FA, suggesting that Nectomys squamipes might have a tolerance threshold to small availability of habitat. Our work is one of the first to use FA to address environmental stress caused by habitat loss in small mammal populations from a Neotropical biome. We suggest that shape FA might serve as a conservation tool to monitor human impact on natural animal populations.

Fluctuating Asymmetry in Morphological Characteristics of Betula Pendula Roth Leaf under Conditions of Urban Ecosystems: Evaluation of the Multi-Factor Negative Impact

The fluctuating asymmetry (FA) in Betula pendula Roth was estimated as an integrated measure of five morphometric characteristics of a lamina. Samples were collected in seven cities that differ both in climatic conditions, moderately to sharply continental. In total, 33 ecotopes were distinguished with various level of anthropogenic load. The statistical data processing involved correlation, one-way and factorial ANOVA, regression analyses, and principal component analysis (PCA). The impact of 25 climatic and anthropogenic factors on the FA value was considered. In most urban ecotopes, the integrated fluctuating asymmetry (IFA) value was higher than in natural biotopes of the same region. No significant inter-annual differences in IFA values were found. FA dependence on traffic load is noted to be statistically significant. The covariation analysis of IFA, climatic, and anthropogenic variables in various urban ecotopes revealed the impact of three groups of factors that together explain 93% of the variance in environmental parameters. The complex analysis clearly arranged the studied ecotopes by pollution gradient and climatic patterns. The primary effect of the total anthropogenic load on the developmental stability of B. pendula results in an IFA increase. IFA can play a key role in bioindication assessment of environmental quality. The climatic factors have no significant effect on the developmental stability of B. pendula in urban conditions.

A dose rate causes no fluctuating asymmetry indexes changes in silver birch (Betula pendula (L.) Roth.) leaves and Scots pine (Pinus sylvestris L.) needles in the Chernobyl Exclusion Zone

The assessment of the fluctuating asymmetry based on measurement of the parameters of left and right parts of silver birch (Betula pendula (L.) Roth.) leaves and relative sizes of pairs of Scots pine (Pinus sylvestris L.) needles from the Chernobyl Exclusion Zone (ChEZ) was carried out. Twelve samples of both birch leaves and pairs of needles were collected from 10 trees at 5 sites in the Chernobyl Exclusion Zone and also at one control site located outside the ChEZ. Values of gamma dose rate in the air varied between the sites from 0.1 to 40 μGy h^-1. Activity concentrations of ⁹⁰Sr and ¹³⁷Cs in the birch leaves varied over the range of 0.9÷2460 kBq kg^-1 and 0.1÷339 kBq·kg^-1 (DW), respectively. In addition to the above, in the Scots pine needles, these ranges were 0.7 ÷1970 kBq kg^-1f for ⁹⁰Sr and 0.1÷78 kBq kg^-1 (DW) for ¹³⁷Cs. From the values of the radionuclides activity concentrations in the plants, the internal dose rate is estimated to be in the range of 0.1 ÷ 274 μGy h^-1. The main sources of the internal dose rate were radiation of ⁹⁰Sr and ⁹⁰Y. Indices of fluctuating asymmetry of silver birch leaves and Scots pine needles varied over the range of 0.048 ± 0.007 ÷ 0.060 ± 0.009 and 0.014 ± 0.002 ÷ 0.018 ± 0.002, respectively, and did not statistically differ for all experimental sites. The indices also did not depend on the external or internal dose rate of ionizing radiation for plants. The above findings seem to be consistent with other research effort in terms of understanding the response of organisms to chronic pollutant exposure and the long-term effects of large scale nuclear accidents.

Scots pine as a promising indicator organism for biomonitoring of the polluted environment: A case study on chronically irradiated populations

In this paper the main results of long-term (2003-2016) observations on Scots pine populations inhabiting sites affected by the Chernobyl accident are presented. Populations growing for many years under chronic radiation exposure are characterized by the enhanced mutation rates, increased genetic diversity, changes in the gene expression and in the level of genome-wide methylation, alterations in the temporal dynamics of cytogenetic abnormalities and genetic structure of populations. However, significant changes at the genetic level had no effects on enzymatic activity, morphological abnormalities, and reproductive ability of pine trees. The results presented increase our understanding of the long-term effects of chronic radiation exposure on plant populations in the wild nature and provide important information for the management and monitoring of radioactively contaminated territories.

Does Chernobyl-derived radiation impact the developmental stability of Asellus aquaticus 30years on?

Effects of long-term, environmentally relevant doses of radiation on biota remain unclear due to a lack of studies following chronic exposure in contaminated environments. The 1986 Chernobyl accident dispersed vast amounts of radioactivity into the environment which persists to date. Despite three decades of research, impacts of the incident on non-human organisms continues to be contested within the scientific literature. The present study assessed the impact of chronic radiation exposure from Chernobyl on the developmental stability of the model aquatic isopod, Asellus aquaticus using fluctuating asymmetry (FA) as an indicator. Fluctuating asymmetry, defined as random deviations from the expected perfect bilateral symmetry of an organism, has gained prominence as an indicator of developmental stability in ecotoxicology. Organisms were collected from six lakes along a gradient of radionuclide contamination in Belarus and the Ukraine. Calculated total dose rates ranged from 0.06-27.1μGy/h. Fluctuating asymmetry was assessed in four meristic and one metrical trait. Significant differences in levels of pooled asymmetry were recorded between sample sites independent of sex and specific trait measured. However, there was no correlation of asymmetry with radiation doses, suggesting that differences in asymmetry were not attributed to radionuclide contamination and were driven by elevated asymmetry at a single site. No correlation between FA and measured environmental parameters suggested a biotic factor driving observed FA differences. This study appears to be the first to record no evident increase in developmental stability of biota from the Chernobyl region. These findings will aid in understanding the response of organisms to chronic pollutant exposure and the long term effects of large scale nuclear incidents such as Chernobyl and Fukushima.

B-chromosome and V-shaped spot asymmetry in the common frog (Rana temporaria L.) populations

The common frog Rana temporaria is characterised by a large variety of colorations and dorsal patterns manifested by a V-shaped spot, which differs in the form, the number of elements and in the regularity. Some populations of R. temporaria are polymorphic for B-chromosome. V-shaped spot asymmetry and B-chromosome occurrence was studied in seven R. temporaria populations inventoried from Belarus country. The analysis of the dorsal V-shaped spot pattern asymmetry in brown frog populations implies that the persistence of additional chromosomes in populations may be one of the factors disturbing the developmental stability of some individuals. Although, Bs may confer some selective advantage to their carriers, which makes them react differently to environmental changes from do non-carriers.

Overview of the cooperation between the Chernobyl Center's International Radioecology Laboratory in Slavutych, Ukraine, and U.S. research centers between 2000 and 2010

The International Radioecology Laboratory (IRL) located in Slavutych, Ukraine, was created in 1999 under the initiative of the United States Government and the Government of Ukraine in the framework of international cooperation on evaluation and minimization of consequences of the Chernobyl nuclear power plant (ChNPP) accident. Since the time the IRL was founded, it has participated in a large number of projects, including the following: 1) study of radionuclide accumulation, distribution, and migration in components of various ecological systems of the Chernobyl Exclusion Zone (ChEZ); 2) radiation dose assessments; 3) study of the effects of radiation influence on biological systems; 4) expert analysis of isotopic and quantitative composition of radioactive contaminants; 5) development of new methods and technologies intended for radioecological research; 6) evaluation of future developments and pathways for potential remediation of the ChEZ areas; 7) assistance in provision of physical protection systems for ionizing irradiation sources at Ukrainian enterprises; 8) reviews of open Russian language publications on issues associated with consequences of the ChNPP accident, radioactive waste management, radioecological monitoring, and ChNPP decommissioning; 9) conduct of training courses on problems of radioecology, radiation safety, radioecological characterization of test sites and environmental media, and research methods; 10) conduct of on-site scientific conferences and workshops on the ChEZ and radioecology problems; participation in off-site scientific conferences and meetings; and 11) preparation of scientific and popular science publications and interactions with mass media representatives. This article provides a brief overview of the major achievements resulting from this cooperation between the IRL and U.S. research centers.

Radiation ecology issues associated with murine rodents and shrews in the Chernobyl exclusion zone

This article describes major studies performed by the Chernobyl Center's International Radioecology Laboratory (Slavutich, Ukraine) on radioecology of murine rodents and shrews inhabiting the Chernobyl Exclusion Zone. The article addresses the long-term (1986-2005) and seasonal dynamics of radioactive contamination of animals and reviews interspecies differences in radionuclide accumulations and factors affecting the radionuclide accumulations. It is shown that bioavailability of radionuclides in the "soil-to-plant" chain and a trophic specialization of animals play key roles in determining their actual contamination levels. The total absorbed dose rates in small mammals significantly reduced during the years following the Chernobyl Nuclear Power Plant accident. In 1986, the absorbed dose rate reached 1.3-6.0 Gy h(-1) in the central areas of the Chernobyl Exclusion Zone (the "Red Forest"). In 1988 and 1990, the total absorbed dose rates were 1.3 and 0.42 Gy h(-1), respectively. In 1995, 2000, and 2005, according to the present study, the total absorbed dose rates rarely exceeded 0.00023, 0.00018, and 0.00015 Gy h(-1), respectively. Contributions of individual radiation sources into the total absorbed dose are described.

Challenging the current strategy of radiological protection of the environment: arguments for an ecosystem approach

The system of radiological protection of the environment that is currently under development is one contribution to the general need to adequately protect the environment against stress. Dominated by operational goals, it emphasizes conceptual and methodological approaches that are readily accessible today: reference organisms supported by individual-based traditional ecotoxicological data. Whilst there are immediate advantages to this approach (pragmatism, consistency with other approaches in use for man and biota), there are also clear limitations, especially in a longer run perspective, that need to be acknowledged and further considered. One can mention a few: uncertainties generated by the need for various extrapolations (from lower to higher levels of biological organisation, ...), various features missed such as potential ecological impact through impairment of ecosystem processes, trans-generational impacts as mediated through genomic instability, indirect effects mediated through trophic interactions or disruption of ecological balances,... Such limitations have already been faced in other fields of environmental protection against other stressors, pushing a number of environment professionals to assign stronger emphasis on more systemic approaches. This review discusses the advantages and limitations of the current approach designed for the radiological protection of non-human biota in the broader context of environment protection as a whole, with especial reference to upcoming trends and evolutions. This leads in particular to advocating the need to boost scientific and methodological approaches featuring the ecosystem concept as a mean to access a unified goal of protection: preserving life sustainability through protection of ecosystem structure and functioning.

Effects of non-human species irradiation after the Chernobyl NPP accident

The area affected by the Chernobyl Nuclear Power Plant accident in 1986 has become a unique test site where long-term ecological and biological consequences of a drastic change in a range of environmental factors as well as trends and intensity of selection are studied in natural settings. The consequences of the Chernobyl accident for biota varied from an enhanced rate of mutagenesis to damage at the ecosystem level. The review comprehensively brings together key data of the long-term studies of biological effects in plants and animals inhabiting over 20 years the Chernobyl NPP zone. The severity of radiation effects was strongly dependent on the dose received in the early period after the accident. The most exposed phytocenoses and soil animals' communities exhibited dose dependent alterations in the species composition and reduction in biological diversity. On the other hand, no decrease in numbers or taxonomic diversity of small mammals even in the most radioactive habitat was shown. In a majority of the studies, in both plant and animal populations from the Chernobyl zone, in the first years after the accident high increases in mutation rates were documented. In most cases the dose-effect relationships were nonlinear and the mutation rates per unit dose were higher at low doses and dose rates. In subsequent years a decline in the radiation background rate occurred faster than reduction in the mutation rate. Plant and animal populations have shown signs of adaptation to chronic exposure. In adaptation to the enhanced level of exposure an essential role of epigenetic mechanisms of gene expression regulation was shown. Based on the Chernobyl NPP accident studies, in the present review attempts were made to assess minimum doses at which ecological and biological effects were observed.

Effects of temperature stress and pesticide exposure on fluctuating asymmetry and mortality of Copera annulata (Selys) (Odonata: Zygoptera) larvae

Although there have been some investigations into the effects of insecticide on the level of fluctuating asymmetry (FA) of adult damselflies, the cooperative effects of environmental factors on FA of larval damselflies were known little. This paper explored effects of exposure to temperature and pesticide on larval development of the damselfly Copera annulata (Selys). A conventional life history trait (mortality) and developmental instability (estimated by calculating fluctuating asymmetry of bilaterally symmetrical structures) were used to measure stresses in this paper. The results showed that temperature and different concentrations of pesticide produced significant effects only on developmental stability of some characters. The FA values of three traits decreased at lower concentrations, then increased slowly with increased insecticide doses. The FA values of four traits decreased slowly with increased temperatures. However, the interaction between different concentrations of insecticide and temperature was complicated and only produced significant effects on five traits. Insecticide treatment did not significantly affect mortality of the larvae of damselfly. However, mortality was significantly positively associated with temperature. There were significantly negative associations between mortality and the FA values of three traits. These results may be caused by higher mortality and short rearing time although we did not find the significant effects of concentrations on mortality. Therefore, we speculate FA may be induced if larval damselflies were treated during longer term and FA has potential as a more specific bioindicator of stresses if we guarantee enough longer rearing time without higher mortality under stressful environment.

Marsupials from space: fluctuating asymmetry, geographical information systems and animal conservation

We report the development of a new quantitative method of assessing the effects of anthropogenic impacts on living beings; this method allows us to assess actual impacts and to travel backwards in time to assess impacts. In this method, we have crossed data on fluctuating asymmetry (FA, a measure of environmental or genetic stress), using Didelphis albiventris as a model, with geographical information systems data relating to environmental composition. Our results show that more impacted environments resulted in statistically higher levels of FA. Our method appears to be a useful and flexible conservation tool for assessing anthropogenic impacts.

On hidden heterogeneity in directional asymmetry - can systematic bias be avoided?

Directional asymmetry (DA) biases the analysis of fluctuating asymmetry (FA) mainly because among-individual differences in the predisposition for DA are difficult to detect. However, we argue that systematic bias mainly results from predictable associations between signed right-left asymmetry and other factors, i.e. from systematic variation in DA. We here demonstrate methods to test and correct for this, by analysing bilateral asymmetry in size and shape of an irregular sea urchin. Notably, in this model system, DA depended significantly on body length and geographic origin, although mean signed asymmetry (mean DA) was not significant in the sample as a whole. In contrast to the systematic variation in DA, undetectable, random variability in the underlying DA mainly leads to reduced statistical power. Using computer simulations, we show that this loss of power is probably slight in most circumstances. We recommend future studies on FA to routinely test and correct for not only as yet for mean DA, but also for systematic variation in DA.