Natural mercury exposure of European insectivorous bats may exceed a recognized toxicity threshold

Heavy metals are an important group of toxic substances harmful for many organisms. Of these, mercury is one of the most monitored in the environment. Several matrices are used for the monitoring of environmental load, including a range of organisms; bats, however, have only been examined rarely. Insectivorous bats are apex predators threatened by several human interventions in their natural environment, including heavy metal pollution. The aim of this study was to analyze the content of total mercury in the fur, flight membrane, and pectoral muscle of greater mouse-eared bats (Myotis myotis). Total mercury concentrations were also measured in carabid beetles from the catch locality Zastávka u Brna. Samples were obtained from 43 bat carcasses at two different localities in the Czech Republic (Zastávka u Brna, Malá Morávka). Total mercury content varied between 1.76-72.20 µg/g in fur, 0.04-0.14 µg/g in skin, and 0.05-0.20 µg/g in muscle. Total mercury values in the fur of some individuals from Malá Morávka exceeded the recognized toxicity limit. Furthermore, there was a significant difference (p < 0.001) in content of total mercury in fur between localities, and there was a clear effect of age on concentrations in fur, skin, and muscle, the concentrations being significantly correlated (fur and skin rs = 0.783; fur and muscle rs = 0.716; skin and muscle rs = 0.884). These findings confirm the usefulness of fur samples from living bats for biomonitoring mercury burden in the environment.

A Review of the Occurrence of Metals and Xenobiotics in European Hedgehogs (Erinaceus europaeus)

Monitoring data from several European countries indicate that European hedgehog (Erinaceus europaeus) populations are declining, and research exploring the causes of the decline, including exposure to potentially harmful xenobiotics and metals, may inform conservation initiatives to protect this species in the wild. Hedgehogs are ground-dwelling mammals, feeding on a range of insects, slugs, snails, and earthworms, as well as eggs, live vertebrates, and carrion, including carcasses of apex predator species representing higher levels of the food chain. Consequently, hedgehogs come into close contact with contaminants present in their habitats and prey. This review investigated the studies available on the subject of the occurrence of metals and organic xenobiotics in hedgehogs. This study found that a vast range of different pesticides; persistent organic pollutants (POPs), including organochlorine compounds and brominated flame retardants (BFRs); as well as toxic heavy metals could be detected. Some compounds occurred in lethal concentrations, and some were associated with a potential adverse effect on hedgehog health and survival. Due to their ecology, combined with the opportunity to apply non-invasive sampling techniques using spines as sampling material, we suggest that the European hedgehog is a relevant bioindicator species for monitoring the exposure of terrestrial wildlife to potential toxicants in urban and rural environments.

Transfer of elements from soil to earthworms and ground beetles in boreal forest

Data on the transfer of elements (such as heavy metals) and their radionuclides into organisms is needed for assessing environmental risks. The current data on many elements, species and environments is limited, but more information can be obtained both from field studies and experimental laboratory studies. However, it is essential to evaluate whether experimental studies adequately predict transfer in natural conditions. Moreover, because of the sparsity of species-specific empirical data, it is a common practice in current radioecological modelling to use data available for related species under the assumption that transfer into organisms is similar within broader taxonomic groups. Earthworms and ground beetles are examples of important invertebrates living near soil surface in terrestrial ecosystems. In this study, the transfer of 34 elements from soil to these organisms was studied in a field study conducted in boreal forest. The earthworm concentrations were compared to the values obtained in an experimental mesocosm study using soil from the field site and were found to be highly correlated. This indicates that the results of mesocosm studies can be used for predicting the transfer of elements from soil to fauna in natural conditions. Furthermore, concentrations in individual earthworm and beetle species were found to be similar to those observed in broader groups of related species, indicating that the generic approach used in current radioecological models may be useful for predicting uptake of elements into single species.

Dietary, locomotory, and metabolic reactions of Abax parallelus (Coleoptera, Carabidae) to acute thiamethoxam intoxication

Carabids (Coleoptera: Carabidae) are abundant predators in ecosystems and serve as pest biocontrol in agroecosystems and forestry. Here we test the impact of thiamethoxam, among the most used neonicotinoids on the consumption rate, locomotion, metabolomics, and oxidative stress level measuring superoxide dismutase (SOD) activity in a predatory carabid, Abax parallelus (Duftschmid, 1812), after acute exposure in the laboratory trials, to get additional data that might link the use of pesticides and predation efficiency. Beetles were exposed to increasing concentrations of thiamethoxam by dipping method, and left to feed overnight prior to the assays. The results showed that individuals treated with higher concentrations of thiamethoxam (20 and 40 mg/L) consumed significantly less food per body weight and had a higher share of intoxicated and moribund individuals. The mass of consumed food per beetle body weight and observed locomotion did not differ significantly between control and groups treated with lower concentrations of thiamethoxam. There are significant differences in concentrations of some metabolites between treated and control individuals, primary in succinate and d-glucose, indicating a disruption in energy production. On the other hand, there is no statistically significant differences in SOD activity among the groups. To conclude, acute exposure to thiamethoxam can result in negative sub-lethal effects in predatory activity and energy budget, while the effects of long-term exposure to lower doses require further research, as well as field assessment on the predation efficiency after pesticide application.

The influence of seabirds on their breeding, roosting and nesting grounds: A systematic review and meta-analysis

Seabird species world-wide are integral to both marine and terrestrial environments, connecting the two systems by transporting vast quantities of marine-derived nutrients and pollutants to terrestrial breeding, roosting and nesting grounds via the deposition of guano and other allochthonous inputs (e.g. eggs, feathers). We conducted a systematic review and meta-analysis and provide insight into what types of nutrients and pollutants seabirds are transporting, the influence these subsidies are having on recipient environments, with a particular focus on soil, and what may happen if seabird populations decline. The addition of guano to colony soils increased nutrient levels compared to control soils for all seabirds studied, with cascading positive effects observed across a range of habitats. Deposited guano sometimes led to negative impacts, such as guanotrophication, or guano-induced eutrophication, which was often observed where there was an excess of guano or in areas with high seabird densities. While the literature describing nutrients transported by seabirds is extensive, literature regarding pollutant transfer is comparatively limited, with a focus on toxic and bioaccumulative metals. Research on persistent organic pollutants and plastics transported by seabirds is likely to increase in coming years. Studies were limited geographically, with hotspots of research activity in a few locations, but data were lacking from large regions around the world. Studies were also limited to seabird species listed as Least Concern on the IUCN Red List. As seabird populations are impacted by multiple threats and steep declines have been observed for many species world-wide, gaps in the literature are particularly concerning. The loss of seabirds will impact nutrient cycling at localized levels and potentially on a global scale as well, yet it is unknown what may truly happen to areas that rely on seabirds if these populations disappear.

Fluctuating Asymmetry as a Method of Assessing Environmental Stress in Two Predatory Carabid Species within Mediterranean Agroecosystems

Fluctuating asymmetry (FA) is used in assessing the effect of environmental stress on the development stability of individuals by measuring small random deviations from perfect bilateral symmetry. Here, we checked for FA on two predatory carabid beetles, Pterostichus melas and Poecilus koyi, in order to evaluate species response to agricultural practices within Mediterranean agroecosystems, as well as FA as a method. The samples were collected in vineyards and olive groves, both under integrated pest management (IPM) and ecological pest management (EPM), and in pristine habitats in the Mediterranean region of Croatia. Geometric morphometrics (GMMs) were used to analyze the pronotum and abdomen shape variations and left–right asymmetries of each population. In respect to the FA measurements, analyzed species responded differently, with P. koyi displaying a lower intensity of FA than P. melas. On the other hand, P. melas beetles from vineyards showed a higher intensity of FA compared with populations from pristine habitats and olive groves. Accordingly, FA pointed out olive groves as potentially less adverse habitats to predatory carabids, keeping in mind the different levels of asymmetry between the two species. Our study singled out P.melas as a more suitable species for further research, in the effect that different agricultural practices can have their impact on non-target invertebrates analyzed by measuring the FA.

Effects of abiotic factors on co-occurring Carabus (Coleoptera: Carabidae) species

The members of the genus Carabus are among the most intensively studied beetle taxa, but many aspects of their autecology are still unexplored. We aimed to study the relationship between measured abiotic parameters and the spatial and temporal distribution of signature carabid species. Carabus assemblages were sampled by pitfalls at six sites belonging to two nearby locations, both forest habitats: in valley and in hill-top position. The sites showed variation in microclimatic and soil characteristics, to which the seven species caught showed specific spatial associations. Carabus scheidleri and C. coriaceus were ubiquitists, occurring at all sites. The habitat specialist C. violaceus germari indicated valley sites with high humidity, lower temperature, limy soil and higher pH, whereas the other specialists, C. nemoralis and C. convexus were strongly associated with the dry, warm, more acidic hill habitat. Remaining species were associated with specific sites and environmental features. The species also exhibited specific phenological patterns corresponding with their habitat preference. Hill habitat species exhibited peak activity density during the hottest summer period, whereas most other species had an activity depression during that period. The results suggest that although Carabus activity density patterns are species specific, they are largely affected by temperature both spatially and temporally.

Synthesis of earthworm trace metal uptake and bioaccumulation data: Role of soil concentration, earthworm ecophysiology, and experimental design

Trace metals can be essential for organo-metallic structures and oxidation-reduction in metabolic processes or may cause acute or chronic toxicity at elevated concentrations. The uptake of trace metals by earthworms can cause transfer from immobilized pools in the soil to predators within terrestrial food chains. We report a synthesis and evaluation of uptake and bioaccumulation empirical data across different metals, earthworm genera, ecophysiological groups, soil properties, and experimental conditions (metal source, uptake duration, soil extraction method). Peer-reviewed datasets were extracted from manuscripts published before June 2019. The 56 studies contained 3513 soil-earthworm trace metal concentration paired data sets across 11 trace metals (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Sb, U, Zn). Across all field and laboratory experiments studied, the median concentrations of Hg, Pb, and Cd in earthworm tissues that were above concentrations known to be hazardous for consumption by small mammals and avian predators but not for Cu, Zn, Cr, Ni, and As. Power regressions show only Hg and Cd earthworm tissue concentrations were well-correlated with soil concentrations with R² > 0.25. However, generalized linear mixed-effect models reveal that earthworm concentrations were significantly correlated with soil concentrations for log-transformed Hg, Cd, Cu, Zn, As, Sb (p < 0.05). Factors that significantly contributed to these relationships included earthworm genera, ecophysiological group, soil pH, and organic matter content. Moreover, spiking soils with metal salts, shortening the duration of exposure, and measuring exchangeable soil concentrations resulted in significantly higher trace metal uptake or greater bioaccumulation factors. Our results highlight that earthworms are able to consistently bioaccumulate toxic metals (Hg and Cd only) across field and laboratory conditions. However, future experiments should incorporate greater suites of trace metals, broader genera of earthworms, and more diverse laboratory and field settings to generate data to devise universal quantitative relationships between soil and earthworm tissue concentrations.

Mercury, Lead and Cadmium Concentrations in Talpa occidentalis and in Their Digeneans of the Genus Ityogonimus

INTRODUCTION

Many parasites living in aquatic ecosystems are useful indicators of environmental health. On the other hand, information is scarcer with respect to the use of helminth parasites of vertebrates living in terrestrial ecosystems as monitoring tools for toxic element environmental pollution. The present study evaluates the suitability of the model Talpa occidentalis/Ityogonimus spp. as a bioindicator system for mercury (Hg), lead (Pb) and cadmium (Cd) contamination in agricultural soils from Asturias (Spain).

METHODS

Kidney and liver samples collected from T. occidentalis specimens (n = 36) and Ityogonimus spp. samples collected from 14 infected hosts were analyzed by ICP-MS.

RESULTS

The highest mean levels of Hg and Pb were found in Ityogonimus individuals (20.9 and 12.4 µg g^-1 wet weight, respectively). Considering renal and hepatic concentrations in T. occidentalis, bioaccumulation factors of Ityogonimus for Hg were 83.7 and 58.6, respectively, whereas concerning Pb bioaccumulation factors were 38.2 and 82.9, respectively. No bioaccumulation was detected in Ityogonimus in the case of Cd.

CONCLUSIONS

More studies involving digenean parasites of small mammals are needed, especially when biomonitoring environmental toxic element pollution in terrestrial ecosystems. The present results support the above-mentioned model as a suitable biomonitoring system to evaluate environmental Hg and Pb contamination in terrestrial non-urban Iberian habitats. Similar models involving other species (Talpa spp./Ityogonimus spp.) might be used in a much wider geographical range.

Molecular gut content analysis of different spider body parts

Molecular gut-content analysis has revolutionized the study of food webs and feeding interactions, allowing the detection of prey DNA within the gut of many organisms. However, successful prey detection is a challenging procedure in which many factors affect every step, starting from the DNA extraction process. Spiders are liquid feeders with branched gut diverticula extending into their legs and throughout the prosoma, thus digestion takes places in different parts of the body and simple gut dissection is not possible. In this study, we investigated differences in prey detectability in DNA extracts from different parts of the spider´s body: legs, prosoma and opisthosoma, using prey-specific PCR and metabarcoding approaches. We performed feeding trials with the woodlouse hunter spider Dysdera verneaui Simon, 1883 (Dysderidae) to estimate the time at which prey DNA is detectable within the predator after feeding. Although we found that all parts of the spider body are suitable for gut-content analysis when using prey-specific PCR approach, results based on metabarcoding suggested the opisthosoma is optimal for detection of predation in spiders because it contained the highest concentration of prey DNA for longer post feeding periods. Other spiders may show different results compared to D. verneaui, but given similarities in the physiology and digestion in different families, it is reasonable to assume this to be common across species and this approach having broad utility across spiders.

Using species-specific enriched stable isotopes to study the effect of fresh mercury inputs in soil-earthworm systems

The fate of mercury (Hg) in the soil-earthworm system is still far from being fully understood, especially regarding recurrent and challenging questions about the importance of the reactivity of exogenous Hg species. Thus, to predict the potential effect of Hg inputs in terrestrial ecosystems, it is necessary to evaluate separately the reactivity of the endogenous and exogenous Hg species and, for this purpose, the use of enriched stable isotope tracers is a promising tool. In the present work, earthworms (Lumbricus terrestris) were exposed to historically Hg contaminated soils from the Almadén mining district, Spain. The soils were either non-spiked, which contain only endogenous or native Hg naturally occurring in the soil, or spiked with isotopically enriched inorganic Hg (¹⁹⁹IHg), representing exogenous or spiked Hg apart from the native one. The differential reactivity of endogenous and exogenous Hg in the soil conditioned the processes of methylation, mobilization, and assimilation of inorganic Hg by earthworms. Both endogenous and exogenous Hg species also behave distinctly regarding their bioaccumulation in earthworms, as suggested by the bioaccumulation factors, being the endogenous methylmercury (MeHg) the species more readily bioaccumulated by earthworms and in a higher extent. To the best of our knowledge, this work demonstrates for the first time the potential of enriched stable isotopes to study the effects of fresh Hg inputs in soil-earthworm systems. The findings of this work can be taken as a case study on the dynamics of Hg species in complex terrestrial systems and open a new door for future experiments.

Metagenomic Analysis of the Gut Microbiome of the Common Black Slug Arion ater in Search of Novel Lignocellulose Degrading Enzymes

Some eukaryotes are able to gain access to well-protected carbon sources in plant biomass by exploiting microorganisms in the environment or harbored in their digestive system. One is the land pulmonate Arion ater, which takes advantage of a gut microbial consortium that can break down the widely available, but difficult to digest, carbohydrate polymers in lignocellulose, enabling them to digest a broad range of fresh and partially degraded plant material efficiently. This ability is considered one of the major factors that have enabled A. ater to become one of the most widespread plant pest species in Western Europe and North America. Using metagenomic techniques we have characterized the bacterial diversity and functional capability of the gut microbiome of this notorious agricultural pest. Analysis of gut metagenomic community sequences identified abundant populations of known lignocellulose-degrading bacteria, along with well-characterized bacterial plant pathogens. This also revealed a repertoire of more than 3,383 carbohydrate active enzymes (CAZymes) including multiple enzymes associated with lignin degradation, demonstrating a microbial consortium capable of degradation of all components of lignocellulose. This would allow A. ater to make extensive use of plant biomass as a source of nutrients through exploitation of the enzymatic capabilities of the gut microbial consortia. From this metagenome assembly we also demonstrate the successful amplification of multiple predicted gene sequences from metagenomic DNA subjected to whole genome amplification and expression of functional proteins, facilitating the low cost acquisition and biochemical testing of the many thousands of novel genes identified in metagenomics studies. These findings demonstrate the importance of studying Gastropod microbial communities. Firstly, with respect to understanding links between feeding and evolutionary success and, secondly, as sources of novel enzymes with biotechnological potential, such as, CAZYmes that could be used in the production of biofuel.

Influence of heavy metal contamination on urban natural enemies and biological control

Urban agriculture is increasing worldwide. A history of contamination within urban landscapes may negatively impact the biota necessary for sustainable crop production, including arthropod natural enemies. This investigation revealed that heavy metal contamination can influence the composition of natural enemy communities and exposure can have reproductive, developmental, immunological and behavioral impacts on predators and parasitoids. Natural enemies exposed to heavy metals typically live shorter lives, take longer to develop and exhibit a reduced reproductive potential. Further, they may incur significant energy costs though the production of detoxification enzymes. This is a new and relatively unexplored area for biological control research, with important implications for our understanding of urban agricultural food web interactions.

Molecular detection of trophic interactions: emerging trends, distinct advantages, significant considerations and conservation applications

The emerging field of ecological genomics contains several broad research areas. Comparative genomic and conservation genetic analyses are providing great insight into adaptive processes, species bottlenecks, population dynamics and areas of conservation priority. Now the same technological advances in high-throughput sequencing, coupled with taxonomically broad sequence repositories, are providing greater resolution and fundamentally new insights into functional ecology. In particular, we now have the capacity in some systems to rapidly identify thousands of species-level interactions using non-invasive methods based on the detection of trace DNA. This represents a powerful tool for conservation biology, for example allowing the identification of species with particularly inflexible niches and the investigation of food-webs or interaction networks with unusual or vulnerable dynamics. As they develop, these analyses will no doubt provide significant advances in the field of restoration ecology and the identification of appropriate locations for species reintroduction, as well as highlighting species at ecological risk. Here, I describe emerging patterns that have come from the various initial model systems, the advantages and limitations of the technique and key areas where these methods may significantly advance our empirical and applied conservation practices.