Risk element accumulation in Coleoptera and Hymenoptera (Formicidae) living in an extremely contaminated area-a preliminary study

Arthropods in landfills and their accumulation potential for toxic elements: A review

Landfills, as a source of potentially toxic elements (PTEs), pose a threat to the environment and human health. A literature review was conducted to explore the diversity of arthropods inhabiting solid waste landfills, as well as on the bioaccumulation of PTEs by arthropods. This review presents scientific papers over the last 20 years. Their importance in landfill ecosystems has been the subject of research; however, the issue of the accumulation of compounds such as toxic elements is emphasized only in a few studies. The bioaccumulation of PTEs was studied for 10 arthropod species that founded in landfills: Orthomorpha coarctata and Trigoniulus corallinus (class Diplopoda), Armadillidium vulgare and Trachelipus rathkii (class Malacostraca), the 6 species of the class Insecta - Zonocerus variegatus, Anacanthotermes ochraceus, Macrotermes bellicosus, Austroaeschna inermis, Calathus fuscipes and Harpalus rubripes.

Can mollusks or insects serve as bioindicators of the risk element polluted area? Gastropods (Gastropoda) versus leaf beetles (Coleoptera: Chrysomelidae)

Two groups of invertebrates, terrestrial mollusks (Gastropoda) and Chrysomela populi leaf beetles (Coleoptera: Chrysomelidae), were sampled to estimate the suitability of these organisms as bioindicators of risk element pollution (predominantly Cd, Pb, and Zn) alongside the risk element concentration gradient in the contaminated area (former mining/smelting areas in the vicinity of Příbram city, Central Bohemia, Czech Republic). The individuals representing ten species of terrestrial snails and imagoes of C. populi were collected manually at five sampling sites, differing in the level of soil contamination with risk elements. The findings showed high variability of the results regardless of the element determined, animal species, and sampling location. Among the elements, higher accumulation ability was observed for Cd and Zn, given the higher bioaccessibility of these elements in soils compared to Pb, Cr, and Cu. Higher Cd and Zn accumulation in the soft tissues of gastropods (without any statistically significant differences among the species) compared to C. populi was also recorded. Medians of the bioaccumulation factors (BAFs) reached up to 33.2 for Cd and 5.8 for Zn, in gastropods while reaching up to 3.4 for Cd, and 2.3 for Zn, for C. populi. For both groups of organisms, paradoxically, a higher rate of accumulation of risk elements was observed in all analyzed organisms in sites with lower soil contamination compared to heavily contaminated sites. This indicated the ability of the organisms living in extreme conditions to avoid the uptake of these elements or to move among areas of different contamination levels. Thus, terrestrial gastropods and C. populi proved to be unsuitable bioindicators for assessing soil pollution.

Arsenic and lead in soil: impacts on element mobility and bioaccessibility

Long-term brown coal mining contributes to risk element contents in soils surrounding coal basins. However, there is a lack of bioaccessibility characterization of the risk elements in the soils at the impacted locations for estimation of the potential health risk, in relation to the effects of soil particle size and element origin. In this study, soils from different geological areas (geogenic vs. anthropogenic) were sampled around the Most brown coal basin, Czech Republic. These soils were passed through sieves to obtain seven aggregate size fractions. For an estimation of the oral bioaccessibility of As and Pb in the size fractions, the physiologically based extraction test was applied, whereas the potential pulmonary bioaccessibility of the elements was estimated by using both Gamble's and Hatch's tests. The results showed that the geochemical pattern of the investigated elements clearly separates the soil samples collected from the mountain region (mineralization from geogenic processes) from those of the basin region (extensive coal mining). For As, the results indicated that it poses higher risks in the anthropogenically affected basin region due to its higher gastro-intestinal and pulmonary bioaccessibility in soil samples in this area. A higher bioaccessibility of As in the soils was recorded in the finer grain size fractions, which are usually air-borne and can be easily ingested and/or inhaled, leading to potential health risks to humans and livestock. The opposite pattern, with a higher content on coarse particles, was recorded for Pb, indicating a potential risk of livestock in the non-forest mountainous areas.

Life in extreme habitats: the number of prepupae per nest of the crabronid wasp Pemphredon fabricii is constant even under pressure from high concentrations of toxic elements

Anthropogenic habitats that are contaminated by toxic elements were recently shown to host abundant and diverse assemblages of bees and wasps (Hymenoptera: Aculeata), including numerous threatened species. However, toxic elements adversely affect insect fitness. We address the effects of toxic elements on aculeate inquilines that occupy Lipara lucens-induced galls on the common reed, Phragmites australis. We hypothesized that contamination of potential nesting and feeding habitats is associated with adverse changes in bee and wasp populations that are attracted in these environments. To address this hypothesis, we analyzed the contents of As, Cd, Cu, Pb, Zn, Fe, and S in site-matched samples of soil, reed galls, and crabronid wasp bodies and correlated them with abundance and species richness of aculeate hymenopterans in reed galls and with the number of larvae in nests of the eudominant hymenopteran, Pemphredon fabricii. The common reed was present at all the examined sites, and L. lucens-induced galls were present at all but one sampling site; the single exception was the sampling site with the highest contents of four of the seven analyzed elements. The alpha diversity of gall-associated aculeate inquilines, abundance of P. fabricii, and number of prepupae per nest of P. fabricii were not correlated with the contents of any of the seven analyzed toxic elements. We found P. fabricii to be abundantly present in habitats with extreme concentrations of toxic elements. Exposed P. fabricii accumulated Cd, Cu, and Pb, while they eliminated Fe and Zn. The obtained data did not support the hypothesis that heavy metal contamination of anthropogenic sites affects P. fabricii and other reed gall-associated aculeates.

Cadmium exposure disrupts the olfactory sensitivity of fire ants to semiochemicals

Ants are eusocial insects and have evolved sensitive chemosensory systems for social communication. However, the effect of heavy metal contamination on the olfactory sensitivity of ants remains largely unknown. Here, we investigated the survival and olfactory response of Solenopsis invicta under cadmium (Cd) exposure. As a result, exposure to dietary Cd at different concentrations (100, 300 and 500 mg/L) caused higher Cd accumulation and lower survival of the ants compared with the control (0 mg/L). Cd exposure induced diverse expression patterns of odor binding protein genes (SiOBPs) in S. invicta antenna. Specifically, the expression of SiOBP4, SiOBP11, SiOBP12 and SiOBP16 was increased by 1.84-, 1.14-, 0.83- and 1.76-fold, respectively, at 300 mg/L Cd, while SiOBP7 and SiOBP9 were suppressed as Cd concentration increased. Electroantennography (EAG) and behavioral bioassays were performed to further evaluate the effect of Cd contamination on the olfactory sensitivity of S. invicta workers to 2, 4, 6-trimethylpyridine (TMP) and 2-ethyl-3,6(5)-dimethylpyrazine (EDP), the two frequent functional semiochemicals for S. invicta. The results showed that under no Cd exposure, S. invicta workers exhibited strong EAG response and apparent residing repellence to TMP and EDP, but Cd exposure suppressed EAG response and deprived the behavioral repellence to TMP and EDP of the workers, suggesting that Cd exposure decreases the olfactory sensitivity of S. invicta to these two functional semiochemicals. Further fluorescence competitive binding assay revealed that SiOBP7 had strong binding affinity to TMP and EDP, suggesting that the decrease in olfactory sensitivity may be attributed to the inhibitory effect of Cd exposure on SiOBP7. Overall, our results suggest that Cd exposure may not only directly decrease the survival of ants, but also affect their olfactory recognition.

Phenotypic Plasticity of Common Wasps in an Industrially Polluted Environment in Southwestern Finland

Simple Summary

Social insects are ecologically and economically important as ecosystem engineers, agricultural pest predators, pollinators, and seed dispersers. Many of the vespid wasps are social insects. Our study species, Common wasp Vespula vulgaris, is native to Finland and classified as invasive in some other parts of the world. The Common wasp have conspicuous yellow and black pigmentation. Their functions and activities in the environment expose the species to environmental pollutants and this study assessed the effect of heavy-metals on common wasps collected from the vicinity of a metal smelter in southwestern Finland. The samples collected were analyzed using various methods such as color morph categorization, electron microscopy, metal analysis, and energy dispersive X-ray analysis (EDX). The methods were used to understand the effects of metal pollution on the species and the adaptive response. Our results indicated phenotypic variation between common wasp samples across the pollution gradient and an adaptive melanin encapsulation process.

Abstract

Insects vary in the degree of their adaptability to environmental contamination. Determining the responses with phenotypic plasticity in ecologically important species in polluted environments will ease further conservation and control actions. Here, we investigated morphological characteristics such as body size, body mass, and color of the common wasp Vespula vulgaris in an industrially polluted environment, considering different levels of metal pollution, and we studied the localization of contaminants in the guts of wasps. We revealed some differences in morphological characteristics and melanization of wasps collected in habitats with high, moderate, and low levels of pollution. The results indicated that V. vulgaris from highly polluted environments had reduced melanin pigmentation on the face but increased melanin pigmentation on the 2nd tergite of the abdomen. In addition, with transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX), we found metal particles from the midgut of wasps originating from the polluted environment. Most of the particles were encapsulated with melanin pigment. This finding confirmed that in wasps, ingested metal particles are accumulated in guts and covered by melanin layers. Our data suggest that wasps can tolerate metal contamination but respond phenotypically with modification of their size, coloration, and probably with the directions of the melanin investments (immunity or coloration). Thus, in industrially polluted areas, wasps might probably survive by engaging phenotypic plasticity with no significant or visible impact on the population.

Current permissible levels of metal pollutants harm terrestrial invertebrates

The current decline of invertebrates worldwide is alarming. Several potential causes have been proposed but metal pollutants, while being widespread in the air, soils and water, have so far been largely overlooked. Here, we reviewed the results of 527 observations of the effects of arsenic, cadmium, lead and mercury on terrestrial invertebrates. These four well-studied metals are considered as priorities for public health and for which international regulatory guidelines exist. We found that they all significantly impact the physiology and behavior of invertebrates, even at levels below those recommended as 'safe' for humans. Our results call for a revision of the regulatory thresholds to better protect terrestrial invertebrates, which appear to be more sensitive to metal pollution than vertebrates. More fundamental research on a broader range of compounds and species is needed to improve international guidelines for metal pollutants, and to develop conservation plans to protect invertebrates and ecosystem services.

Assessment of legacy mine metal contamination using ants as indicators of contamination

Most legacy mines contributed to contamination of the environment before and after cessation of mining. Contamination from waste rock, slag and tailings can introduce large concentrations of metals and metalloids to the surface soil and downstream sediments. Since ants are able to accumulate metals in their bodies, we investigated the possibility of using the elemental compositions of ants as indicators of metals at legacy mines developed on ores rich in copper (Cu), zinc (Zn), arsenic (As), silver (Ag) and lead (Pb). Our results showed the concentrations of manganese (Mn) and Cu in ants were not significantly different between mine and reference samples and only Zn was significantly different between contaminated and reference areas. Crematogaster spp. and Notoncus spp. from reference areas accumulated larger concentrations of metals in their bodies compared to ants from the mine. Ants accumulated metals in different parts of their bodies. The abdomen was the main site for accumulation of Mn, iron (Fe) and Zn. Mandibles were only associated with accumulation of Zn. Copper and Pb showed no area of preferential accumulation and traces were detected in the whole body of the ants. Ants from five genera had similar regions for metal accumulation. The exoskeleton did not contribute to accumulation of metals; instead all metals were stored in internal organs. Not all genera were suitable for use as indicators; only Iridomyrmex spp. and Ochetellus spp. accumulated larger amount of metals in mine samples compared to reference samples.

Accumulation of metals in Lasius niger: Implications for using ants as bioindicators

The high capacity of many ant species to accumulate trace metals raises the question of whether the metal concentration in ants' bodies could reliably reflect the contamination of ecosystems. The idea of applying the metal accumulation in ants for bioindication purposes is tempting; however, the methods should consider that ants are unique organisms due to their social way of life. In this study, we describe the between-colony variation in the accumulation of Zn and Cd in workers of the common garden ant Lasius niger originated from the post-mining area of a zinc-and-lead smelter in southern Poland. We show that the accumulation of both metals differs significantly between colonies even within the same study site; at the maximum, we detected a three-fold difference in Zn accumulation and a six-fold difference in Cd. The results showed that in the study area, the capacity of L. niger to accumulate metals is highly colony-specific. If future studies on other ant species concur with our findings, this may suggest that incorporating the between-colony variation of metal accumulation in prospective bioindication protocols would provide a higher accuracy of the assessments on the contamination of impacted environments. We suggest that using ants for bioindication should be preceded by preliminary studies to assess representative samples of colonies that could reliably indicate the contamination of the investigated area.

Impact of extreme events on pollinator assemblages

Insect pollinators face a number of well-documented threats that challenge their survival at an individual and community level. The effect of extreme events on pollinator assemblages has received little attention to date, partly due to a lack of consensus on what constitutes extreme, but also because robust pre-event data is often lacking. Here, the term SHOCK (Sudden, High-magnitude Opportunity for a Catastrophic 'Kick') is used to encompass attributes of extreme events that carry the potential to add additional challenges to insect communities already facing environmental stressors. Selected events from two SHOCK categories are explored (those with natural origins and those that are human-mediated). The value of studying single events is considered in the context of a third category; human-enhanced SHOCKs.

Pollution intensity-dependent metal accumulation in ground beetles: a meta-analysis

Survival of organisms in polluted habitats is a key factor regarding their long-term population persistence. To avoid harmful physiological effects of pollutants' accumulation in organisms, decontamination and excretion could be effective mechanisms. Among invertebrates, ground beetles are reliable indicators of environmental pollution. Published results, however, are inconsistent, as some studies showed effective decontamination and excretion of pollutants, while others demonstrated severe toxic symptoms due to extreme accumulation. Using ground beetles as model organisms, we tested our pollution intensity-dependent disposal hypothesis for five pollutants (Cd, Cu, Mn, Pb, and Zn) among four soil pollution intensity levels (low, moderate, high, and extreme) by categorical meta-analysis on published data. According to our hypothesis, decontamination and excretion of pollutants in ground beetles are effective in lowly or moderately polluted habitats, while disposal is ineffective in highly or extremely polluted ones, contributing to intense accumulation of pollutants in ground beetles. In accordance with the hypothesis, we found that in an extremely polluted habitat, accumulation of Cd and Pb in ground beetles was significantly higher than in lowly polluted ones. These findings may suggest the entomoremediation potential of ground beetles in an extremely polluted environment.