Folsomia candida (Collembola): a "standard" soil arthropod

Ecotoxicological impact of deactivated asbestos-cement on soil ecosystems

The effects of thermally deactivated asbestos cement (DAC) on the soil ecosystem were evaluated using the soil model organism Folsomia candida (Collembola). Two materials were obtained by treating asbestos cement slates, commonly used for roofing, at 1100 °C under oxidizing conditions (Red DAC) and at 1150 °C under reducing conditions (Green DAC). Ten age-synchronized juveniles of F. candida were exposed to DAC powder:soil mixtures in ratios of 1:1 and 1:10 for both types. After 28 days, adults and juveniles were counted to assess treatment effects. The results indicate distinct toxicity profiles. The Red powder did not induce adult lethality at the tested concentrations; however, a significant reduction in juvenile production was observed at the higher concentration (1:1). In contrast, the Green powder caused adult lethality at 1:1 concentration, with no juveniles produced. Both materials contain a high percentage of silica glass (∼40% by weight), a well-known insect dehydration agent and mechanical insecticide. At the highest concentration, silica glass may cause detrimental effects on juveniles, which are more sensitive to dehydration than adults. Green DAC also contains 8.5% lime (CaO), an antimicrobial and insecticidal agent that can disrupt soil pH. The combination of silica-induced dehydration and lime-mediated alkalinity may account for the lethal effects of Green DAC on F. candida adults. These findings reinforce the need for proper DAC recycling. While asbestos deactivation effectively eliminates its hazard in the built environment, improper disposal or soil contamination may pose ecological risks. Recycling DAC into stable matrices, such as ceramics or mortar, minimizes environmental contamination while promoting circular economy.

Elevated temperature magnifies the toxicity of imidacloprid in the collembolan, Folsomia candida

Global warming subjects soil organisms to elevated temperature stress, while simultaneously altering the detoxification processes for pollutants within these organisms. The combined stressors of increased temperature and pollutants may impose synergistic stress on soil fauna, necessitating detailed investigation. Here, we exposed Collembola (Folsomia candida) to imidacloprid (a neonicotinoid pesticide) in combination with a range of constant temperatures in a full-factorial experimental design to assess the integrated impacts on survival, growth, and bioaccumulation. The results revealed that high temperatures and imidacloprid synergistically inhibited the survival of F. candida. Under 6.4 mg/kg imidacloprid exposure, survival rates decreased by 41.38 % at 30.2 °C and 68.75 % at 30.5 °C, compared to the same temperature treatments without imidacloprid exposure. Bayesian model analysis confirmed a significant synergistic interaction between imidacloprid and temperature on survival. Interestingly, at elevated temperatures, the internal concentration of imidacloprid in F. candida significantly decreased, while the soil concentration of the insecticide remained stable. This suggests that the observed synergistic effect is not due to increased pollutant accumulation within F. candida at higher temperatures, but rather the exhaustion of energy resources needed for detoxification and thermal stress management. This dual-stressor-induced energy competition underpins the synergistic interactions observed. Our findings highlight the significant synergistic effects of high temperatures and imidacloprid on Collembola, underscoring an increased ecological risk under such conditions.

Combining multi-surface and biotoxicity models to predict cadmium bioavailability and accumulation in a soil collembolan

The link between internal metal concentrations in soil animals and external metal concentrations is a critical issue in soil ecotoxicity tests and involves metal transfer from solid-liquid interfaces to target soil animals. Soil cadmium (Cd) pollution is a major concern, the bioavailability of Cd to the model soil collembolan Folsomia candida was therefore determined in naturally Cd-contaminated soils by chemical extraction methods and mechanism-based multi-surface models (MSMs). Three combined models were also developed by combining MSMs with a free ion activity model (MSMs-FIAM), a modified biotic ligand model (MSMs-rBLM), and a Gouy-Chapman-Stern model (MSMs-GCSM) to predict Cd bioaccumulation in F. candida in a mechanistic way. MSMs gave better prediction results for Cd bioavailability to F. candida (determination coefficient, R2 = 0.667) than other chemical extraction methods (0.01 M CaCl2, 0.43 M HNO3, soil solution, DGT, and soil total Cd). MSMs calculated dissolved Cd is an effective indicator of bioavailable Cd to F. candida and allowed prediction under a wide range of soil properties. The combined model MSMs-rBLM more successfully predicted Cd bioaccumulation in F. candida (R2 = 0.793, root-mean-square error (RMSE) = 0.172, mean absolute percentage error (MAPE) = 15.4 %) than other combined models and linked the soil-liquid interfaces to the surface of the target soil animal. MSMs-rBLM model may be a new tool for the prediction of Cd ecological risks and bioaccumulation in soils.

Soil Decomposer Can Regulate the Legacy Effect of Photodegradation on Forest Marcescent Litter Decomposition, but Emerging Microplastics Disrupt This

Photodegradation-photochemical mineralization of standing litters-often exerts a legacy effect aiding biodegradation in soil (PLE), which is overlooked in deciduous forests containing marcescent leaves. Meanwhile, increasing anthropogenic microplastics have deposited in forests, how they would affect the PLE on subsequent litter bio-decomposition is currently unknown. Here, we employed an ultraviolet-accelerated aging chamber to replicate the abiotic photodegradation process of a naturally marcescent tree, Lindera glauca, then manipulated mesocosm bio-incubations to quantify how decomposers (microbial alone or with soil animals) and microplastic contamination would interactively affect the PLE. We found abiotic photodegradation significantly decreased litter lignin content before and after the bio-incubation. During an early phase decomposition, lignin lost greatly and displayed a crucial role in determining the ways that soil animal and photodegradation affect the bio-decomposition. Microbial decomposer alone led to a positive PLE universally. Soil animals depressed microbial biomass and inhibited the microbial-mediated PLE in unpolluted mesocosms but intensified the PLE in contaminated soils. We conclude that decomposer interactions can attenuate PLE, but microplastics will disrupt the established equilibrium, making contaminated soil more susceptible to photodegradation-induced litter chemical changes. This promotes integration of radiation and emerging pollution to further our understanding of biogeochemical cycle in forest ecology.

Survival and reproduction effects of microplastics from three agricultural mulching films on Folsomia candida, Sinella curviseta, Heteromurus nitidus and Ceratophysella denticulata (Collembola)

An estimated 467 kt of plastic used in agriculture annually end up in European soils, potentially breaking down into secondary microplastics (MPs). Not much is known about the possible effects of these MPs on organisms residing in the soil. To properly assess their environmental risk, experimental data is needed on the toxicity of MPs to the survival and reproduction of model organisms. This study aimed at assessing the toxicity of three MP types derived from commonly used agricultural plastics to different Collembola species, representing an important and highly diverse class of soil arthropods. Starch- polybutadiene adipate terephthalate blend (starch-PBAT blend) MPs were produced from mulching films that were artificially aged by mechanical recycling. MPs were also made from virgin low density polyethylene (LDPE) mulching films and from linear low density polyethylene (LLDPE) films that underwent the same mechanical recycling process as the starch-PBAT blend films. Four Collembola species were tested: Folsomia candida, Sinella curviseta, Heteromurus nitidus and Ceratophysella denticulata, representing epedaphic, hemiedaphic and euedaphic, as well as sexually reproducing and parthenogenetic species. Each species was exposed in Lufa 2.2 soil spiked with nine MP concentrations: 0.0016, 0.008, 0.04, 0.2, 1, 2, 3, 4 and 5 % (w/w dry soil) and a control without additional MPs added to the soil. No dose-dependent effects were found for any of the exposed organisms, to any of the MPs tested. The results of this study suggest that the MPs used in this study, derived from commonly applied agricultural plastics, do not pose an immediate hazard to Collembola.

Ecotoxicity of bioinsecticide spinosad to soil organisms: Commercial formulation versus active ingredient

Spintor® (SPIT®) is a commercial formulation of a bioinsecticide with the active ingredient Spinosad (SPIN). Despite the efforts of regulatory agencies, there still is a lack of information regarding short- and long-term exposures to soil-dwellers, as well as effects at environmentally relevant concentrations. This work aimed to evaluate the effects of SPIT® and SPIN, on the oligochaete Eisenia fetida, and the arthropod Folsomia candida. For this, natural soil was spiked with environmentally relevant concentrations (0.00-1.49 mg of the active ingredient·kg-1 of dry soil) to assess avoidance behaviour in E. fetida and reproduction effects on both species. Further, in E. fetida adults exposed for 2- and 28-day biomarkers of oxidative stress, energetic reserves, neurotoxicity and genotoxicity were evaluated. A significant reduction in juvenile production for F. candida was observed for SPIT® at ≥0.66 mg kg-1 and SPIN at ≥0.13 mg kg-1, and although no effect was observed on E. fetida reproduction, the oligochaeta revealed a tendency to avoid soil spiked with SPIT® at 0.44, 0.66 and 1.49 mg kg-1. The sub-individual responses of E. fetida demonstrate genotoxicity upon exposure to SPIT® and SPIN for 2 days. The 2-day exposures of SPIT® and SPIN seem to induce defence mechanisms, and in general, SPIN exerted higher effects than SPIT® on the oligochaetes. Overall, the pro-oxidant performance and energy metabolism pathways were disrupted in both exposures to SPIT® and SPIN. The results suggest that spinosyns-based products can have an impact on soil arthropods F. candida and oligochaete's health, possibly affecting their essential functions in terrestrial ecosystems.

Unveiling the environmental impact of tire wear particles and the associated contaminants: A comprehensive review of environmental and health risk

This review offers a novel perspective on the environmental fate and ecotoxicological effects of tire wear particles (TWPs), ubiquitous environmental contaminants ranging in size from micrometers to millimeters (averaging 10-100 micrometers). These particles pose a growing threat due to their complex chemical composition and potential toxicity. Human exposure primarily occurs through inhalation, ingesting contaminated food and water, and dermal contact. Our review delves into the dynamic interplay between TWP composition, transformation products (TPs), and ecological impacts, highlighting the importance of considering both individual chemical effects and potential synergistic interactions. Notably, our investigation reveals that degradation products of certain chemicals, such as diphenylguanidine (DPG) and diphenylamine (DPA), can be more toxic than the parent compounds, underscoring the need to fully understand these contaminants' environmental profile. Furthermore, we explore the potential human health implications of TWPs, emphasizing the need for further research on potential respiratory, cardiovascular, and endocrine disturbances. Addressing the challenges in characterizing TWPs, assessing their environmental fate, and understanding their potential health risks requires a multidisciplinary approach. Future research should prioritize standardized TWP characterization and leachate analysis methods, conduct field studies to enhance ecological realism, and utilize advanced analytical techniques to decipher complex mixture interactions and identify key toxicants. By addressing these challenges, we can better mitigate the environmental and health risks associated with TWPs and ensure a more sustainable future.

The functional evolution of collembolan Ubx on the regulation of abdominal appendage formation

Folsomia candida is a tiny soil-living arthropod belonging to the Collembola, which is an outgroup to Insecta. It resembles insects as having a pair of antennae and three pairs of thorax legs, while it also possesses three abdominal appendages: a ventral tube located in the first abdominal segment (A1), a retinaculum in A3, and a furca in A4. Collembolan Ubx and AbdA specify abdominal appendages, but they are unable to repress appendage marker gene Dll. The genetic basis of collembolan appendage formation and the mechanisms by which Ubx and AbdA regulate Dll transcription and appendage development remains unknown. In this study, we analysed the developmental transcriptomes of F. candida and identified candidate appendage formation genes, including Ubx (FcUbx). The expression data revealed the dominance of Dll over Ubx during the embryonic 3.5 and 4.5 days, suggesting that Ubx is deficient in suppressing Dll at early appendage formation stages. Furthermore, via electrophoretic mobility shift assays and dual luciferase assays, we found that the binding and repression capacity of FcUbx on Drosophila Dll resembles those of the longest isoform of Drosophila Ubx (DmUbx_Ib), while the regulatory mechanism of the C-terminus of FcUbx on Dll repression is similar to that of the crustacean Artemia franciscana Ubx (AfUbx), demonstrating that the function of collembolan Ubx is intermediate between that of Insecta and Crustacea. In summary, our study provides novel insights into collembolan appendage formation and sheds light on the functional evolution of Ubx. Additionally, we propose a model that collembolan Ubx regulates abdominal segments in a context-specific manner.

Dissection of the synthesis of polyunsaturated fatty acids in nematodes and Collembola of the soil fauna

It is becoming increasingly clear that not only unicellular, photoautotrophic eukaryotes, plants, and fungi, but also invertebrates are capable of synthesizing ω3 long-chain polyunsaturated fatty acids (LC-PUFA) de novo. However, the distribution of this anabolic capacity among different invertebrate groups and its implementation at the gene and protein level are often still unknown. This study investigated the PUFA pathways in common soil fauna, i.e. two nematode and two Collembola species. Of these, one species each (Panagrellus redivivus, Folsomia candida) was assumed to produce ω3 LC-PUFA de novo, while the others (Acrobeloides bodenheimeri, Isotoma caerulea) were supposed to be unable to do so. A highly labeled oleic acid (99 % 13C) was supplemented and the isotopic signal was used to trace its metabolic path. All species followed the main pathway of lipid biosynthesis. However, in A. bodenheimeri this terminated at arachidonic acid (ω6 PUFA), whereas the other three species continued the pathway to eicosapentaenoic acid (ω3 PUFA), including I. caerulea. For the nematode P. redivivus the identification and functional characterization of four new fatty acid desaturase (FAD) genes was performed. These genes encode the FAD activities Δ9, Δ6, and Δ5, respectively. Additionally, the Δ12 desaturase was analyzed, yet the observed activity of an ω3 FAD could not be attributed to a coding gene. In the Collembola F. candida, 11 potential first desaturases (Δ9) and 13 front-end desaturases (Δ6 or Δ5 FADs) have been found. Further sequence analysis indicates the presence of omega FADs, specifically Δ12, which are likely derived from Δ9 FADs.

Insect frass from upcycling vegetable by-products with cereals: Effects on the soil properties, plant development and soil invertebrate fitness

The use of insects in organic management systems is expanding due to their ability to recycle waste into valuable co-products for agriculture, notably frass, constituted by the insect's excrements, larval exuviae, and remaining undigested feedstock. This study aimed to assess the effects of different application rates of frass (0.16, 0.32, 0.64, 1.28, 2.56 and 5.12%) produced by black soldier fly Hermetia illucens larvae (BSFL) on the survival and reproduction of two non-target invertebrate species, the enchytraeid Enchytraeus crypticus and the collembolan Folsomia candida, and early development of three representative species of crops as onion Allium cepa, turnip Brassica rapa and tomato Solanum lycopersicum. Chemical analyses were conducted to evaluate changes in the soil properties. Results showed that BSFL frass did not impact the invertebrates' survival while significantly enhancing the production of E. crypticus juveniles (after 21 days). F. candida juveniles remained similar (after 28 days). Seed germination decreased at the highest frass rate (5.12%), while the development was promoted at intermediate rates (0.64%-1.28%). The different outcomes may be linked to changes in certain soil parameters, such as the soil pH and electrical conductivity, the soil organic matter, and the availability of nutrients. In summary, frass posed no risk to the tested invertebrate species but may hinder seed germination at high rates, representing a risk for agricultural production. Nevertheless, intermediate rates of BSFL frass promoted plant development, showing potential as a sustainable alternative to conventional fertilizers. Further research is needed to ensure its safe and efficient application in agriculture.

Silence is not always golden: A closer look at potential environmental and ecotoxicological impacts of large-scale dsRNA application

RNA interference (RNAi) technology has emerged as a pivotal strategy in sustainable pest management, offering a targeted approach that significantly mitigates the environmental and health risks associated with traditional insecticides. Originally implemented through genetically modified organisms (GMOs) to produce specific RNAi constructs, the technology has evolved in response to public and regulatory concerns over GMOs. This evolution has spurred the development of non-transgenic RNAi applications such as spray-induced gene silencing (SIGS), which employs double-stranded RNA (dsRNA) to silence pest genes directly without altering the plant's genetic makeup. Despite its advantages in specificity and reduced ecological footprint, SIGS faces significant obstacles, particularly the instability of dsRNA in field conditions, which limits its practical efficacy. To overcome these limitations, innovative delivery mechanisms have been developed. These include nanotechnology-based systems, minicells, and nanovesicles, which are designed to protect dsRNA from degradation and enhance its delivery to target organisms. While these advancements have improved the stability and application efficiency of dsRNA, comprehensive assessments of their environmental safety and the potential for increased exposure risks to non-target organisms remain incomplete. This comprehensive review aims to elucidate the environmental fate of dsRNA and evaluate the potential risks associated with its widespread application on non-target organisms, encompassing soil microorganisms, beneficial insects, host plants, and mammals. The objective is to establish a more refined framework for RNAi risk assessment within environmental and ecotoxicological contexts, thereby fostering the development of safer, non-transgenic RNAi-based pest control strategies.

Effects of mycotoxin-producing fungi on the fitness and gut bacterial community of the soil springtail Folsomia candida

Mycotoxin-producing fungi are widespread and their adverse effects on mammals have been investigated; however, their impacts on soil invertebrates are not fully understood. Folsomia candida is a model soil arthropod that represents an important part of the soil invertebrate community. This study investigated the consequences of F. candida grazing on mycotoxin-producing fungi Fusarium verticillioides, F. graminearum, Aspergillus ochraceus, and A. nidulans. Consuming mycotoxin-producing fungi affected the body size and reproductive ability of F. candida, and altered the gut bacterial composition, with decreased Proteobacteria and increased Actinobacteria (Microbacterium) abundances. Notably, the abundance of foodborne fungi can be detected. Furthermore, certain bacteria isolated from F. candida's gut inhibited the growth of corresponding mycotoxin-producing fungi. The gut bacteria that inhibited mycotoxin-producing fungi growth in Aspergillus groups were also associated with poor fitness parameters and larger disruption in gut microbiota. Importantly, switching back to yeast diets reversed both the fitness parameters and gut bacterial composition. Together, our study demonstrated that grazing of mycotoxin-producing fungi by F. candida resulted in reduced physiological parameters and disturbed the gut bacterial community, and those changes can be restored by switching back to yeast diets, which indicates a strong resilience of springtails to mycotoxin-producing fungi.

IMPORTANCE

Mycotoxin-producing fungi are widespread in nature and raise concerns for human and livestock health. Although they share the same ecosystem, interactions between mycotoxin-producing fungi and soil arthropods are not well understood. In this study, we report an unexpected finding that the soil arthropod Folsomia candida is rather tolerant to these mycotoxin-producing fungi. F. candida can survive solely on mycotoxin-producing fungi as a food source with reduced physiological parameters. Moreover, the gut microbial community is disturbed by mycotoxin-producing fungi, and some of the bacteria isolated from F. candida's gut can inhibit the growth of corresponding fungi. Notably, the altered physiological parameters and gut microbiota are restored when a normal diet is reintroduced, suggesting F. candida's resilience to mycotoxin-producing fungi. These findings clarify the impact of toxin-producing diets on F. candida, shedding light on how organisms can build resilience to environmental stimuli.

A Dirt(y) World in a Changing Climate: Importance of Heat Stress in the Risk Assessment of Pesticides for Soil Arthropods

The rise in global temperatures and increasing severity of heat waves pose significant threats to soil organisms, disrupting ecological balances in soil communities. Additionally, the implications of environmental pollution are exacerbated in a warmer world, as changes in temperature affect the uptake, transformation and elimination of toxicants, thereby increasing the vulnerability of organisms. Nevertheless, our understanding of such processes remains largely unexplored. The present study examines the impact of high temperatures on the uptake and effects of the fungicide fluazinam on the springtail Folsomia candida (Collembola, Isotomidae). Conducted under non-optimum but realistic high temperatures, the experiments revealed that increased temperature hampered detoxification processes in F. candida, enhancing the toxic effects of fluazinam. High temperatures and the fungicide exerted synergistic interactions, reducing F. candida's reproduction and increasing adult mortality beyond what would be predicted by simple addition of the heat and chemical effects. These findings highlight the need to reevaluate the current ecological risk assessment and the regulatory framework in response to climate changes. This research enhances our understanding of how global warming affects the toxicokinetics and toxicodynamics (TK-TD) of chemicals in terrestrial invertebrates. In conclusion, our results suggest that adjustments to regulatory threshold values are necessary to address the impact of a changing climate.

Survival and reproduction tests using springtails reveal weathered petroleum hydrocarbon soil toxicity in boreal ecozone

Survival and reproduction tests were conducted using two native springtail (subclass: Collembola) species to determine the toxicity of a fine-grained (< 0.005 - 0.425 mm) soil from an industrial site located in the Canadian boreal ecozone. Accidental petroleum hydrocarbon (PHC) release continuously occurred at this site until 1998, resulting in a total hydrocarbon concentration of 12,800 mg/kg (soil dry weight). Subfractions of the PHC-contaminated soil were characterized using Canadian Council of Ministers of the Environment Fractions, which are based on effective carbon numbers (nC). Fraction 2 (> nC10 to nC16) was measured at 8400 mg/kg and Fraction 3 (> nC16 to nC34) at 4250 mg/kg in the contaminated soil. Age-synchronized colonies of Folsomia candida and Proisotoma minuta were subject to 0%, 25%, 50%, 75%, and 100% relative contamination mixtures of the PHC-contaminated and background site soil (< 100 mg/kg total PHCs) for 28 and 21 days, respectively. Survival and reproduction decreased significantly (Kruskal-Wallis Tests: p < 0.05, df = 4.0) in treatments of the contaminated site soil compared to the background soil. In both species, the most significant decline in survival and reproduction occurred between the 0% and 25% contaminated soil. Toxicity responses in the two springtails were ascribed to the standardized test design, short lifespans, and high fecundity in both species. This study showed that 25 + years of soil weathering has not eliminated the toxicity of fine-grained PHC-contaminated soil on two native terrestrial springtail species. Adverse effects to springtail health were attributed to exposure to soils dominated by genotoxic PHC Fraction 2 compounds and slow weathering processes due to the cold climate at the site.

Assessing the ecotoxicological effects of novel cellulose nanocrystalline glitter compared to conventional polyethylene terephthalate glitter: Toxicity to springtails (Folsomia candida)

Glitter is a type of microplastic, and thus there is a need to assess its potential impacts on the environment and to assess the potential for non-plastic cellulose nanocrystal structurally colored glitters as safe and sustainable replacements. The ecotoxicity of glitter has been mostly ignored in the research literature, with only a few published studies focusing on aquatic organisms. Therefore, an exposure experiment was conducted to examine the impact of conventional polyethylene terephthalate (PET) glitter as well as untreated and heat-treated cellulose nanocrystal (CNC) based glitter on the survival, reproduction, and length of Folsomia candida (springtail). Folsomia candida reproduction was reduced by 61% (P = 0.013) after exposure to PET glitter at 1000 mg/kg, while no significant effects were observed on F. candida survival and length. In contrast, there were no significant impacts on F. candida survival, length, or reproduction when exposed to untreated or heat-treated CNC glitter. These results indicate that exposure to PET glitter may impact soil invertebrates at the population level, and that CNC glitter has potential as a biodegradable non-plastic alternative to PET glitter to decrease detrimental effects on soil ecosystems.

Does copper contamination change thermotaxis of the soil arthropod Folsomia candida (Collembola)?

Behavioural thermoregulation (thermotaxis) is essential for soil invertebrates to evade thermal extremes in terrestrial environments. Extensive and continuous use of copper (Cu) based products has led to elevated Cu concentration in soils across the globe and in some areas reaching concentrations that are hazardous to soil invertebrates. We hypothesised that environmental stressors, for example, exposure to heavy metals may compromise the adaptive behavioural thermoregulation of organisms, but very little is known of such interactions. In this study, we chose Cu as a model toxicant and investigated the potential effect of Cu-contaminated soils on the behavioural thermoregulation of springtails (Folsomia candida). We measured the distribution of springtails when placed on a temperature gradient ranging from 6 to 46 °C and estimated their thermal preference as an indicator of behavioural thermoregulation. Results showed that within 60 min of being introduced to the thermal gradient, the distribution of springtails was unimodal with slight skewness towards high temperature. Springtails exhibited a consistent preferred temperature range of approximately 21-23 °C across all Cu exposure levels and time points. However, Cu contamination increased the frequency of springtails recorded along the gradient where temperature was above 30 °C. We interpreted this observation as Cu-exposed animals having an elevated risk of entering heat coma and not being able to evade noxious temperatures. We conclude that Cu contamination does not alter the thermal preference of F. candida but compromises their ability to tolerate extreme high temperature. Incorporating behavioural responses into ecotoxicological assessments provides ecologically relevant insights into the impacts of chemical pollution on soil ecosystems.

Assessing the multi-dimensional impact of lead-induced toxicity on collembola found in maize fields: From oxidative stress to genetic disruptions

The prolonged exposure of agricultural soils to heavy metals from wastewater, particularly in areas near industrial facilities, poses a significant threat to the well-being of living organisms. The World Health Organization (WHO) has established standard permissible limits for heavy metals in agricultural soils to mitigate potential health hazards. Nevertheless, some agricultural fields continue to be irrigated with wastewater containing industrial effluents. This study aimed to assess the concentration of lead in soil samples collected from agricultural fields near industrial areas. Subsequently, we determined the lethal concentration (LC50) of lead (Pb) and other heavy metals for two Collembola species, namely Folsomia candida, a standard organism for soil ecotoxicity tests, and comparing it with Proisotoma minuta. The research further examined the toxic effects of lead exposure on these two species, revealing depletion in the energy reservoirs and alterations in the tissue histology of both organisms. The study revealed that lead can induce genotoxic damage as it evidently has moderate binding affinity with the ct-DNA and hence can cause DNA fragmentation and the formation of micronuclei. Elevated lipid peroxidation (LPO) levels and protein carbonylation levels were observed, alongside a reduction in antioxidant enzymes (CAT, SOD & GPx). These findings suggest that lead disrupts the balance between oxidants and the antioxidant enzyme system, impairing defense mechanisms and consequential derogatory damage within microarthropods. The investigation elucidates a complex network of various signaling pathways compromised as a result of lead toxicity. Hence, it presents a novel perspective that underscores the pressing necessity for implementing an integrated risk assessment framework at the investigated site.

Characterization of Springtail (Arrhopalites caecus) for Use in Soil Ecotoxicity Testing

Springtails (subclass: Collembola) represent one of the most extensively studied invertebrate groups in soil ecotoxicology. This is because of their ease of laboratory culture, significant ecological role, and sensitivity to environmental contaminants. Folsomia candida (family: Isotomidae) is a globally widespread parthenogenetic species that is prevalent in laboratory toxicity testing with springtails. Conversely, Arrhopalites caecus (family: Arrhopalitidae), a parthenogenic globular springtail species, remains untested in soil ecotoxicology. This species is found in diverse habitats, including cave systems and forest leaf litter, and has a global distribution. The sensitivity of A. caecus to environmental contaminants, such as neonicotinoid insecticides, as well as its life history and optimal culturing conditions, are largely unknown. The present study describes the establishment of a pure A. caecus laboratory culture and characterization of its life cycle and culturing conditions. We assessed the sensitivity of A. caecus to various insecticides, including exposures to the neonicotinoid thiamethoxam in soil and through a novel feeding assay as well as to clothianidin and cyantraniliprole in spiked soil exposures. In 7- and 14-day exposures to thiamethoxam in agricultural soil, the 50% lethal concentration (LC50) values were determined to be 0.129 mg/kg dry weight and 0.010 mg/kg dry weight, respectively. The 14-day LC50 for exposure to thiamethoxam via spiked food was determined to be 0.307 mg/kg dry weight. In addition, the 28-day 50% effect concentration for inhibition of juvenile production from cyantraniliprole exposure in the same soil type was 0.055 mg/kg dry weight. Challenges encountered in using this species included susceptibility to mite infestation and low adult survival rates in the 28-day cyantraniliprole test. Environ Toxicol Chem 2024;43:1820-1835. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Acclimation temperature influences the thermal sensitivity of injury accumulation in Folsomia candida at extreme low and high temperatures

The importance of thermal acclimation for the Thermal Death Time (TDT) landscape of the common soil living springtail, Folsomia candida (Collembola, Isotomidae), was investigated. To this aim, we acclimated adult springtails at 10 °C (cold-acclimation) and 20 °C (warm-acclimation), respectively. In static thermal tolerance assays, we found the relationship between survival and exposure time at a number of stressful high and low temperatures. Using logistic modelling, we found, at each exposure temperature, the time until 50% mortality had been reached (Lt50). The exponential functions of TDT curves were found by linear regression of log10 Lt50 values against exposure temperature. Results showed that cold acclimation significantly increased cold tolerance and increased the temperature dependence of cold injury accumulation rate (increased the slope by 4 orders of magnitude) in F. candida. Hence, cold acclimation changed the status of this species from chill-susceptible to moderately chill-tolerant. The cellular injury accumulation at sub-zero temperatures was not related to freezing of body water in this study. Congruently, we found a significant negative effect of cold acclimation on heat tolerance and that cold acclimation decreased the thermal sensitivity of the heat injury accumulation rate. Different slopes of the TDT curves between acclimation groups indicated that acclimation shifted the proportional importance of cellular injury mechanisms or the nature of injury mechanisms. Finally, we compare and combine the TDT curves at extreme high and low temperatures with previously published results on longevity at benign temperatures (from 0 to 30 °C) and describe the full thermal niche of F. candida.

Ageing influences the toxicity of two innovative nanofertilizers to the soil invertebrates Enchytraeus crypticus and Folsomia candida

The increasing global food demand is threatening the sustainability of agrifood production systems. The intensification of agricultural practices, with inadequate use of pesticides and fertilizers, poses major challenges to the good functioning of agroecosystems and drastically degrades the soil quality. Nanotechnology is expected to optimize the current farming practices and mitigate some associated impacts. Layered double hydroxides (LDHs) are a class of nanomaterials with high potential for use in agricultural productions, mostly due to their sustained release of nutrients. Considering its novelty and lack of studies on the terrestrial ecosystem, it is essential to assess potential long-term harmful consequences to non-target organisms. Our study aimed to evaluate the effect of Zn-Al-NO3 LDH and Mg-Al-NO3 LDH ageing on the survival and reproduction of two soil invertebrate species Enchytraeus crypticus and Folsomia candida. We postulated that the toxicity of nanomaterials to soil invertebrates would change with time, such that the ageing of soil amendments would mediate their impacts on both species. Our results showed that the toxicity of LDHs was species-dependent, with Zn-Al-NO3 LDH being more toxic to E. crypticus, while Mg-Al-NO3 LDH affected more F. candida, especially in the last ageing period, where reproduction was the most sensitive biological parameter. The toxicity of both nanomaterials increased with ageing time, as shown by the decrease of the EC50 values over time. The influence of LDH dissolution and availability of Zn and Mg in the soil pore water was the main factor related to the toxicity, although we cannot rule out the influence of other structural constituents of LDHs (e.g., nitrates and aluminium). This study supports the importance of incorporating ageing in the ecotoxicity testing of nanomaterials, considering their slow release, as effects on soil organisms can change and lead to more severe impacts on the ecosystem functioning.

Temperature-size responses during ontogeny are independent of progenitors' thermal environments

Background

Warming generally induces faster developmental and growth rates, resulting in smaller asymptotic sizes of adults in warmer environments (a pattern known as the temperature-size rule). However, whether temperature-size responses are affected across generations, especially when thermal environments differ from one generation to the next, is unclear. Here, we tested temperature-size responses at different ontogenetic stages and in two consecutive generations using two soil-living Collembola species from the family Isotomidae: Folsomia candida (asexual) and Proisotoma minuta (sexually reproducing).

Methods

We used individuals (progenitors; F0) from cultures maintained during several generations at 15 °C or 20 °C, and exposed their offspring in cohorts (F1) to various thermal environments (15 °C, 20 °C, 25 °C and 30 °C) during their ontogenetic development (from egg laying to first reproduction; i.e., maturity). We measured development and size traits in the cohorts (egg diameter and body length at maturity), as well as the egg diameters of their progeny (F2). We predicted that temperature-size responses would be predominantly determined by within-generation plasticity, given the quick responsiveness of growth and developmental rates to changing thermal environments. However, we also expected that mismatches in thermal environments across generations would constrain temperature-size responses in offspring, possibly due to transgenerational plasticity.

Results

We found that temperature-size responses were generally weak in the two Collembola species, both for within- and transgenerational plasticity. However, egg and juvenile development were especially responsive at higher temperatures and were slightly affected by transgenerational plasticity. Interestingly, plastic responses among traits varied non-consistently in both Collembola species, with some traits showing plastic responses in one species but not in the other and vice versa. Therefore, our results do not support the view that the mode of reproduction can be used to explain the degree of phenotypic plasticity at the species level, at least between the two Collembola species used in our study. Our findings provide evidence for a general reset of temperature-size responses at the start of each generation and highlight the importance of measuring multiple traits across ontogenetic stages to fully understand species' thermal responses.

Toxicity mechanisms of plastic nanoparticles in three terrestrial species: antioxidant system imbalance and neurotoxicity

The detrimental impacts of plastic nanoparticles (PNPs) are a worldwide concern, although knowledge is still limited, in particular for soil mesofauna. This study investigates the biochemical impact of 44 nm polystyrene PNPs on three soil models-Enchytraeus crypticus (Oligochaeta), Folsomia candida (Collembola) and Porcellionides pruinosus (Isopoda). Exposure durations of 3, 7 and 14 days (d) were implemented at two concentrations (1.5 and 300 mg kg-1 PNPs). Results revealed PNPs impact on the activities of the glutathione-dependent antioxidative enzyme, glutathione S-transferase (GST) and on the neurotransmitter acetylcholinesterase (AChE) for all three species. Catalase (CAT) played a minor role, primarily evident in F. candida at 300 mg kg-1 PNPs (CAT and GST response after 14 d), with no lipid peroxidation (LPO) increase. Even with the antioxidant defence, P. pruinosus was the most sensitive species for lipid oxidative damage (LPO levels increased after 7 d exposure to 300 mg kg-1 PNPs). Significant AChE inhibitions were measured already after 3 d to both PNP concentrations in F. candida and E. crypticus, respectively. Significant AChE inhibitions were also found in P. pruinosus but later (7 d). Overall, the toxicity mechanisms of PNPs involved antioxidant imbalance, being (mostly) the glutathione-associated metabolism part of that defence system. Neurotoxicity, linked to AChE activities, was evident across all species. Sensitivity to PNPs varied: P. pruinosus > F. candida ≅ E. crypticus. This pioneering study on PNPs toxicity in soil invertebrates underscores its environmental relevance, shedding light on altered biochemical responses, that may compromise ecological roles and soil ecosystem fitness.

Molecular level toxicity effects of As(V) on Folsomia candida: Integrated transcriptomics and metabolomics analyses

Arsenic (As) is a widespread metalloid with well-known toxicity. To date, numerous studies have focused on individual level toxicity (e.g., growth and reproduction) of As to typical invertebrate springtails in soils, however, the molecular level toxicity and mechanism was poorly understood. Here, an integrated transcriptomics and metabolomics approach was used to reveal responses of Folsomia candida exposed to As(V) of 10 and 60 mg kg-1 at which the individual level endpoints were influenced. Transcriptomics identified 5349 and 4020 differentially expressed genes (DEGs) in low and high concentration groups, respectively, and the most DEGs were down-regulated. Enrichment analysis showed that low and high concentrations of As(V) significantly inhibited chromatin/chromosome-related biological processes (chromatin/chromosome organization, nucleosome assembly and organization, etc.) in springtails. At high concentration treatment, structural constituent of cuticle, chitin metabolic process and peptidase activity (serine-type peptidase activity, endopeptidase activity, etc.) were inhibited or disturbed. Moreover, the apoptosis pathway was significantly induced. Metabolomics analysis identified 271 differential changed metabolites (DCMs) in springtails exposed to high concentration of As. Steroid hormone biosynthesis was the most significantly affected pathway. Several DCMs that related to chitin metabolism could further support above transcriptomic results. These findings further extended the knowledge of As toxic mechanisms to soil fauna and offer important information for the environmental risk assessment.

Cadmium toxicity to and accumulation in a soil collembolan (Folsomia candida): major factors and prediction using a back-propagation neural network model

Accurate prediction of cadmium (Cd) ecotoxicity to and accumulation in soil biota is important in soil health. However, very limited information on Cd ecotoxicity on naturally contaminated soils. Herein, we investigated soil Cd ecotoxicity using Folsomia candida, a standard single-species test animal, in 28 naturally Cd-contaminated soils, and the back-propagation neural network (BPNN) model was used to predict Cd ecotoxicity to and accumulation in F. candida. Soil total Cd and pH were the primary soil properties affecting Cd toxicity. However, soil pH was the main factor when the total Cd concentration was < 3 mg kg-1. Interestingly, correlation analysis and the K-spiked test confirmed nutrient potassium (K) was essential for Cd accumulation, highlighting the significance of studying K in Cd accumulation. The BPNN model showed greater prediction accuracy of collembolan survival rate (R2 = 0.797), reproduction inhibitory rate (R2 = 0.827), body Cd concentration (R2 = 0.961), and Cd bioaccumulation factor (R2 = 0.964) than multiple linear regression models. Then the developed BPNN model was used to predict Cd ecological risks in 57 soils in southern China. Compared to multiple linear regression models, the BPNN models can better identify high-risk regions. This study highlights the potential of BPNN as a novel and rapid tool for the evaluation and monitoring of Cd ecotoxicity in naturally contaminated soils.

Exploring ecological effects of arsenic and cadmium combined exposure on cropland soil: from multilevel organisms to soil functioning by multi-omics coupled with high-throughput quantitative PCR

Arsenic (As) and cadmium (Cd) pose potential ecological threats to cropland soils; however, few studies have investigated their combined effects on multilevel organisms and soil functioning. Here, we used collembolans and soil microbiota as test organisms to examine their responses to soil As and Cd co-contamination at the gene, individual, and community levels, respectively, and further uncovered ecological relationships between pollutants, multilevel organisms, and soil functioning. At the gene level, collembolan transcriptome revealed that elevated As concentrations stimulated As-detoxifying genes AS3MT and GST, whereas the concurrent Cd restrained GST gene expression. At the individual level, collembolan reproduction was sensitive to pollutants while collembolan survival wasn't. At the community level, significant but inconsistent correlations were observed between the biodiversity of different soil keystone microbial clusters and soil As levels. Moreover, soil functioning related to nutrient (e.g., carbon, nitrogen, phosphorus, and sulfur) cycles was inhibited under As and Cd co-exposure only through the mediation of plant pathogens. Overall, these findings suggested multilevel bioindicators (i.e., AS3MT gene expression in collembolans, collembolan reproduction, and biodiversity of soil keystone microbial clusters) in cropland soils co-contaminated with As and Cd, thus improving the understanding of the ecotoxicological impact of heavy metal co-contamination on soil ecosystems.

Multixenobiotic response of Collembola to soil contamination, the phisiological basis for bioindicative environmental monitoring

Collembola are well-established models in ecotoxicological research, extensively employed to investigate the effects of various contaminants, including heavy metals. The Multixenobiotic Resistance Mechanism (MXR) is a physiological response based on transmembrane efflux proteins that play a pivotal role in pumping xenobiotics and conferring resistance. This mechanism is firmly established as a biomarker of aquatic contamination and has recently shown promise as a soil biomonitoring tool. In this study, we aimed to assess the feasibility of utilizing the MXR mechanism as a biomonitoring tool, specifically by investigating the response of two Collembola species exposed to soil contaminated in a real-life situation. Soil samples were obtained from the site of Brazil's largest mine disaster, a dam rupture in Brumadinho-MG. We explored MXR activity in the model species Folsomia candida and a tropical native species, Cyphoderus sp. Our findings reveal efflux activity in both species, confirmed by model MXR protein inhibitors. Moreover, we observed distinct MXR activity levels corresponding to the degree of heavy metal contamination in the soil samples. Consequently, our results underscore the potential of combining an established soil bioindicator, such as Collembola, with the physiological response of a molecular biomarker like MXR. This approach may represent a valuable strategy for biomonitoring terrestrial ecosystems.

Effect of zinc-biochar composite aging on its physicochemical and ecotoxicological properties

The stability of Zn-biochar composites is determined by environmental factors, including the aging processes. This paper focused on the ecotoxicological evaluation of Zn-biochar (Zn-BC) composites subjected to chemical aging. Pristine biochars and composites produced at 500 or 700 °C were incubated at 60 and 90 °C for six months. All biochars were characterized in terms of their physicochemical (elemental composition, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and porous structure), ecotoxicological properties (tested with Folsomia candida and Aliivibrio fischeri) and contaminant content (polycyclic aromatic hydrocarbons (PAH), heavy metals (HM) and environmentally persistent free radicals (EPFR)). An increase in the number of surface oxygen functional groups and increased hydrophilicity and polarity of all Zn-BC composites were observed due to oxidation during aging. It was also found that Zn-BC aging at 90 °C resulted in a 28-30% decrease in solvent-extractable PAHs (Ʃ16 Ctot PAHs) compared to nonaged composites. The aging process at both temperatures also caused a 104 fold reduction in EPFRs in Zn-BC composites produced at 500 °C. The changes in the physicochemical properties of Zn-BC composites after chemical aging at 90 °C (such as pH and HM content) caused an increase in the toxicity of the composites to Folsomia candida (reproduction inhibition from 19 to 24%) and Aliivibrio fischeri (luminescence inhibition from 96 to 99%). The aging of composites for a long time may increase the adverse environmental impact of BC-Zn composites due to changes in physicochemical properties (itself and its interactions with pollutants) and the release of Zn from the composite.

Discovering the deep evolutionary roots of serum amyloid A protein family

Deep evolutionary origin of the conserved animal serum amyloid A (SAA) apolipoprotein family leading to yet unknown highly similar SAA-like sequences occurring in certain bacterial genomes is demonstrated in this contribution. Horizontal gene transfer event of corresponding genes between gut bacteria and non-vertebrate animals was discovered in the reconstructed phylogenetic tree obtained with maximum likelihood and neighbor-joining methods, respectively. This detailed phylogeny based on totally 128 complete sequences comprised diverse serum amyloid A isoforms from various animal vertebrate and non-vertebrate phyla and also corresponding genes coding for highly similar proteins from animal gut bacteria. Typical largely conserved sequence motifs and a peculiar structural fold consisting mainly of four α-helices in a bundle within all reconstructed clades of the SAA protein family are discussed with respect to their supposed biological functions in various organisms that contain corresponding genes.

Soil habitat function after innovative nanoagriproducts application: Effect of ageing on the avoidance behaviour of the soil invertebrates Enchytraeus crypticus and Folsomia candida

Research on nanotechnology with applications in agriculture has been gathering attention because it may achieve a good balance between agricultural production and environmental integrity. Among the vast nanomaterials, layered double hydroxides (LDHs) are a promising solution for supplying crops with macro- and/or micronutrients. Still, little is known about their safety implications for non-target organisms, such as soil invertebrates. The habitat function of soils might be impacted by potential stressors, which can be assessed through avoidance behaviour tests. This study aimed to assess the effect of two innovative agriproducts, Zn-Al-NO3 LDH and Mg-Al-NO3 LDH, on the avoidance behaviour of the enchytraeid Enchytraeus crypticus and the collembolan Folsomia candida, over time. Simultaneously, Zn and Mg potential release from LDHs to soil was evaluated. Overall, the behaviour of soil invertebrates differed between species, with enchytraeids being more sensitive to LDHs-treated soils than collembolans, possibly explained by their different physiological traits. The behaviour of soil organisms also depended on the LDH structural composition and was time-variable. Soil treated with Zn-Al-NO3 LDH was perceived as less favourable compared to Mg-Al-NO3 LDH, which was preferred to clean soil at most tested concentrations. LDHs toxicity was partly, but not exclusively, related to Zn and Mg release. Cations release over time was demonstrated in the chemical assessment. Still, LDHs toxicity to soil invertebrates decreased as increasing AC50 values were derived over time. Slower dissolution over time might explain the decrease in toxicity. Our study demonstrates that both soil invertebrates could sense LDHs in soil and eventually adapt their behaviour by avoiding or preferring, according to the type and level of LDH present.

Evaluation of the ecotoxicological effects of biogenic amines derived from cadaverous putrefaction on springtails Folsomia candida

Necro-leachate, a liquid released during cadaveric decomposition, is considered the main culprit for impacts on cemetery environments. The biogenic amines cadaverine and putrescine make up part of the composition of necro-leachate and have a certain toxicity to different organisms. Springtails are among the most used bioindicators to assess the impacts of soil contaminants. As there are no data on the acute and chronic toxicity of springtails exposed to cadaverine and putrescine, the objective of this study was to evaluate the toxic potential of both amines, under the behavioral effect of avoidance and reproduction in the species Folsomia candida. Springtails were exposed to soils contaminated with different concentrations of cadaverine and putrescine, and different mixtures of these amines. To evaluate the avoidance and reproduction test, the individuals were exposed for periods of 48 h and 28 days, respectively. The results obtained in the avoidance test showed that springtails exhibited a preference for the treated soil in both isolated and mixed treatments. The chronic evaluation assays showed that the reproduction was affected, particularly in the treatments with combined amines, resulting in a reduction in the total number of juveniles. From the results, it is possible to infer that the methods applied in this research have provided information that will contribute to a better understanding of the toxicity of putrefactive biogenic amines, since there exist few ecotoxicological studies carried out with these amines, and especially with those from cemetery environments.

Environmental risk assessment of PPP application in European soils and potential ecosystem service losses considering impacts on non-target organisms

The use of Plant Protection Products (PPPs) is leading to high exposure scenarios with potential risk to soil organisms, including non-target species. Assessment of the effects of PPPs on non-target organisms is one of the most important components of environmental risk assessment (ERA) since they play crucial functions in ecosystems, being main driving forces in different soil processes. As part of the framework, EFSA is proposing the use of the ecosystem services approach for setting specific protection goals. In fact, the services provided by soil organisms can be impacted by the misuse of PPPs in agroecosystems. The aim of this work was to assess PPPs potential risk upon ecosystem services along European soils, considering impacts on earthworms and collembola. Four well-known (2 insecticides-esfenvalerate and cyclaniliprole- and 2 fungicides - picoxystrobin and fenamidone-) worst case application (highest recommended application) were studied; exploring approaches for linked observed effects with impacts on ecosystem services, accounting for their mode of action (MoA), predicted exposure, time-course effects in Eisenia fetida and Folsomia sp. and landscape variability. The selected fungicides exerted more effects than insecticides on E. fetida, whereas few effects were reported for both pesticides regarding Folsomia sp. The most impacted ecosystem services after PPP application to crops appeared to be habitat provision, soil formation and retention, nutrient cycling, biodiversity, erosion regulation, soil remediation/waste treatment and pest and disease regulation. The main factors to be taken into account for a correct PPP use management in crops are discussed.

Transcriptome analysis of a springtail, Folsomia candida, reveals energy constraint and oxidative stress during petroleum hydrocarbon exposure

Petroleum hydrocarbon (PHC) contamination in soil is ubiquitous and poses harmful consequences to many organisms. The toxicity of PHC-impacted soil is difficult to predict due to variations in mixture composition and the impacts of natural weathering processes. Hence, high-throughput methods to assess PHC-impacted soils is required to expedite land management decisions. Next-generation sequencing is a robust tool that allows researchers to investigate the effects of contaminants on the transcriptome of organisms and identify molecular biomarkers. In this study, the effects of PHCs on conventional endpoints (i.e., survival and reproduction) and gene expression rates of a model springtail species, Folsomia candida were investigated. Age-synchronized F. candida were exposed to ecologically-relevant concentrations of soils spiked with fresh crude oil to calculate the reproductive EC25 and EC50 values using conventional toxicity testing. Soils spiked to these concentrations were then used to evaluate effects on the F. candida transcriptome over a 7-day exposure period. RNA-seq analysis found 98 and 132 differentially expressed genes when compared to the control for the EC25 and EC50 treatment groups, respectively. The majority of up-regulated genes were related to xenobiotic biotransformation reactions and oxidative stress response, while down-regulated genes coded for carbohydrate and peptide metabolic processes. Promotion of the pentose phosphate pathway was also found. Results suggest that the decreased reproduction rates of F. candida exposed to PHCs is due to energy constraints caused by inhibition of carbohydrate metabolic processes and allocation of remaining energy to detoxify xenobiotics. These findings provide insights into the molecular effects in F. candida following exposure to crude oil for seven days and highlight their potential to be used as a high-throughput screening test for PHC-contaminated sites. Adverse molecular effects can be measured as early as 24 h following exposure, whereas conventional toxicity tests may require a minimum of four weeks.

New Insights into Nanoplastics Ecotoxicology: Effects of Long-Term Polystyrene Nanoparticles Exposure on Folsomia candida

Despite the growing concern over nanoplastics' (NPls) environmental impacts, their long-term effects on terrestrial organisms remain poorly understood. The main aim of this study was to assess how NPls exposure impacts both the parental (F1) and subsequent generations (F2 and F3) of the soil-dwelling species Folsomia candida. After a standard exposure (28 days), we conducted a multigenerational study along three generations (84 days), applying polystyrene nanoparticles (PS NPs; diameter of 44 nm) as representatives of NPls. Endpoints from biochemical to individual levels were assessed. The standard test: PS NPs (0.015 to 900 mg/kg) had no effect in F. candida survival or reproduction. The multigenerational test: PS NPs (1.5 and 300 mg/kg) induced no effects on F. candida survival and reproduction along the three generations (F1 to F3). PS NPs induced no effects in catalase, glutathione reductase, glutathione S-transferases, and acetylcholinesterase activities for the juveniles of the F1 to F3. Oxidative damage through lipid peroxidation was detected in the offspring of F1 but not in the juveniles of F2 and F3. Our findings underscore the importance of evaluating multigenerational effects to gain comprehensive insights into the contaminants long-term impact, particularly when organisms are continuously exposed, as is the case with NPls.

Ecotoxicological assessment of natural soil amended with sewage sludge: the impacts on soil edaphic organisms and microbial community

Sewage sludge usage as agricultural soil amendment is a well-known practice employed worldwide. However, certain components may pose risks to the soil ecosystem. For a better verification of the potential adverse effects on the soil biota, biological assays have become an indispensable tool for an accurate understanding of the residue's behavior on soil, as well as its potential toxicity. Accordingly, to properly assess the effects of natural tropical soil (Oxisoil) amended with sewage sludge, we conducted toxicological tests with edaphic organisms (Enchytraeus crypticus and Folsomia candida) and microbial biomass (through respirometric assessment). Results indicate that E. crypticus and F. candida present similar reproduction sensitivity behavior to sewage sludge. For the microbiological analysis, the results suggest that microbial activity was stimulated by sludge application. For further evaluation of respiration of the microbial community and CO2 stabilization values behavior, Ford-Walford modeling was applied and presented limit values for sludge application in soil for 1.5 g kg-1 and 15.0 g kg-1 of, approximately, 55 mg and 88 mg, respectively. CO2 releases were faster and reached stability within 18 weeks for the soil with higher sludge content (15.0 g kg-1 of dry soil). In contrast, CO2 releases were slower for the soil with lower sludge content (1.5 g kg-1 of dry soil), and until the experiment's final period (21 weeks) respiration behavior did not reach stability. This study indicates that the stabilized sewage sludge, at the considered recommended application rate, presents a low toxicity risk for the studied bioindicators, being suitable for agricultural use.

Additive and dose-dependent mixture effects of Flumite 200 (flufenzin, acaricide) and Quadris (azoxystrobin, fungicide) on the reproduction and survival of Folsomia candida (Collembola)

Chemical plant protection is still a dominant agricultural practice in the world, and usually fields are treated with several pesticides many times per year. This means that not only the single substances affect the environment and the non-target organisms, but their mixtures. Our model organism was Folsomia candida (Collembola). We aimed to gain information on the toxicity of Quadris (azoxystrobin) and Flumite 200 (flufenzine aka. diflovidazine) on survival and reproduction and whether the animals can mitigate the toxicity with soil and/or food avoidance behaviour. Also, we aimed to test the effect of the mixture of these two pesticides. We used the OECD 232 reproduction test, a soil avoidance test, and a food choice test for both single pesticides and their mixture. We prepared the mixtures based on the concentration addition model, so the 50% effective concentrations (EC50) of the single materials were used as one toxic unit with a constant ratio of the two materials in the mixture. In the end, the measured mixture EC and LC (lethal concentration) values were compared to the estimate of the concentration addition model. Both materials were toxic to the Collembola in much higher concentrations than the recommended field concentrations (Flumite 200 EC50: 1.096, LC50: 1.561, Quadris EC50: 65.568, LC50: 386.165 mg kg-1). The springtails did not consistently avoid the polluted soils, this only happened in higher concentrations. The mixtures seemed to have additive effects on the reproduction and we found dose-dependent interaction with the survival (EC50: 1.022 Toxic Unit, 0.560 Flumite 200 and 33.505 Quadris; LC50: 1.509 Toxic Unit, 0.827 Flumite 200 and 49.471 mg kg-1 Quadris). The deviation from the concentration addition model suggests that the curve starts with a synergy. but above EC50 it becomes antagonistic. We conclude that both Quadris and Flumite 200 are safe for springtails until the recommended field concentration is respected. However, if higher concentrations are used the animals cannot avoid Flumite 200 and the toxic effects can fully manifest. Consequently, the dose-dependent deviation from the concentration addition model is a reason for caution as the low concentrations were synergistic for survival. That means the field concentrations can possibly cause synergistic effects. However, to clarify that further tests are necessary.

Effects of litter quality on foraging behaviour and demographic parameters in Folsomia candida (Collembola)

Litter quality has long been associated with demographic parameters of Collembola populations. However, little is known about the capacity of Collembola to perceive and seek better litter quality. To address this gap, three complementary laboratory experiments were carried out with the Collembola Folsomia candida. First, populations were fed on three different types of leaf litters (Quercus pubescens, Acer opalus and Prunus avium) and a control (agar-agar-brewer's yeast mixture) for 6 weeks to assess their impacts on demography (reproduction rate and population size). Second, the body length of individuals differentially fed with the same four types of resources was measured to assess a functional trait that can potentially affect movement parameters such as prospected area or foraging speed. Third, F. candida single individuals were exposed to the same litter quality gradient and placed at an increasing distance from the litter (from 1 to 5 cm). For 10 min, their foraging behaviour was recorded which included prospected area, foraging speed, perception distance and success in reaching the litter (foraging success). As expected, low-quality litter (i.e. Q. pubescens) contributed to low population growth compared to the control treatment and the high-quality litters (P. avium and A. opalus). In the third experiment, the probability of finding the resource was negatively correlated to the distance, but was unrelated to the litter quality and the Collembola body length. When resource was perceived, F. candida was able to switch from non-directional to directional movements, with a large variability in the perception distance from a few millimetres to several centimetres. Taken together, our results indicate that litter quality plays a relevant role in Collembola demographic parameters once the population settles on litter patch, but not on foraging behaviour to select high-quality resources.

A new insight into the potential drivers of antibiotic resistance gene enrichment in the collembolan gut association with antibiotic and non-antibiotic agents

Effects of non-antibiotic pharmaceuticals on antibiotic resistance genes (ARGs) in soil ecosystem are still unclear. In this study, we explored the microbial community and ARGs variations in the gut of the model soil collembolan Folsomia candida following soil antiepileptic drug carbamazepine (CBZ) contamination, while comparing with antibiotic erythromycin (ETM) exposure. Results showed that, CBZ and ETM all significantly influenced ARGs diversity and composition in the soil and collembolan gut, increasing the relative abundance of ARGs. However, unlike ETM, which influences ARGs via bacterial communities, exposure to CBZ may have primarily facilitated enrichment of ARGs in gut through mobile genetic elements (MGEs). Although soil CBZ contamination did not pose an effect on the gut fungal community of collembolans, it increased the relative abundance of animal fungal pathogens contained therein. Soil ETM and CBZ exposure both significantly increased the relative abundance of Gammaproteobacteria in the collembolan gut, which may be used to indicate soil contamination. Together, our results provide a fresh perspective for the potential drivers of non-antibiotic drugs on ARG changes based on the actual soil environment, revealing the potential ecological risk of CBZ on soil ecosystems involving ARGs dissemination and pathogens enrichment.

Corridor quality buffers extinction under extreme droughts in experimental metapopulations

Corridors with good-quality habitats maintain the spatial dynamics of metapopulations by promoting dispersal between habitat patches, potentially buffering populations, and communities against continued global change. However, this function is threatened by habitats becoming increasingly fragmented, and habitat matrices becoming increasingly inhospitable, potentially reducing the resilience and persistence of populations. Yet, we lack a clear understanding of how reduced corridor quality interacts with rates of environmental change to destabilize populations. Using laboratory microcosms containing metapopulations of the Collembola Folsomia candida, we investigate the impact of corridor quality on metapopulation persistence under a range of simulated droughts, a key stressor for this species. We manipulated both drought severity and the number of patches affected by drought across landscapes connected by either good- or poor-quality corridors. We measured the time of metapopulation extinction, the maximum rate of metapopulation decline, and the variability of abundance among patches as criteria to evaluate the persistence ability of metapopulations. We show that while drought severity negatively influenced the time of metapopulation extinction and the increase in drought patches caused metapopulation decline, these results were mitigated by good-quality corridors, which increased metapopulation persistence time and decreased both how fast metapopulations declined and the interpatch variability in abundances. Our results suggest that enhancing corridor quality can increase the persistence of metapopulations, increasing the time available for conservation actions to take effect, and/or for species to adapt or move in the face of continued stress. Given that fragmentation increases the isolation of habitats, improving the quality of habitat corridors may provide a useful strategy to enhance the resistance of spatially structured populations.

Paraquat is toxic to the soil-dwelling arthropod, Folsomia candida (Collembola: Isotomidae), and has potential effects on its Wolbachia endosymbiont

The springtail, Folsomia candida, is a soil arthropod commonly used to evaluate environmental toxins. Conflicting data on the toxicity of the herbicide paraquat prompted re-evaluation of its effects on F. candida survival and reproduction. Paraquat has an LC₅₀ of about 80 μM when tested in the absence of charcoal; charcoal, often used in test arenas to facilitate visualization of the white Collembola, has a protective effect. Survivors of paraquat treatment fail to resume molting and oviposition, suggesting an irreversible effect on the Wolbachia symbiont that restores diploidy during parthenogenetic reproduction of this species.

Neutral Dietary Effects of Two MicroRNAs, Csu-Novel-260 and Csu-Mir-14, on the Non-Target Arthropod Folsomia candida

RNA interference (RNAi) that is triggered by small or short RNAs has shown enormous potential in the development of pest control strategies. Two microRNAs (miRNAs), Csu-novel-260 and Csu-miR-14, were used in insect-resistant genetically engineered (IRGE) rice lines to confer resistance to Chilo suppressalis. However, a risk assessment of RNAi-based products is essential to determine the safety of a biopesticide or IRGE crop for commercialization. The non-target organism Folsomia candida, which plays an important ecological role as a soil decomposer in agricultural ecosystems, was used to assess the risk of miRNAs Csu-novel-260 and Csu-miR-14. In this study, a dietary miRNA toxicity assay system was established in F. candida. The expression levels of target genes, survival rate, fecundity and body size were investigated to evaluate the effects of the miRNAs on F. candida under the worst-case scenario. The results showed that the dietary miRNA toxicity assay system could be used for risk assessment of miRNA in F. candida. The target genes of miRNAs were influenced by miRNA at some time points. However, no significant differences were observed in the life-table parameters in F. candida fed with a diet containing miRNAs. The dietary effects of two miRNAs on F. candida are neutral.

Wolbachia springs eternal: symbiosis in Collembola is associated with host ecology

Wolbachia are endosymbiotic alpha-proteobacteria infecting a wide range of arthropods and nematode hosts with diverse interactions, from reproductive parasites to obligate mutualists. Their taxonomy is defined by lineages called supergroups (labelled by letters of the alphabet), while their evolutionary history is complex, with multiple horizontal transfers and secondary losses. One of the least recently derived, supergroup E, infects springtails (Collembola), widely distributed hexapods, with sexual and/or parthenogenetic populations depending on species. To better characterize the diversity of Wolbachia infecting springtails, the presence of Wolbachia was screened in 58 species. Eleven (20%) species were found to be positive, with three Wolbachia genotypes identified for the first time in supergroup A. The novel genotypes infect springtails ecologically and biologically different from those infected by supergroup E. To root the Wolbachia phylogeny, rather than distant other Rickettsiales, supergroup L infecting plant-parasitic nematodes was used here. We hypothesize that the ancestor of Wolbachia was consumed by soil-dwelling nematodes, and was transferred horizontally via plants into aphids, which then infected edaphic arthropods (e.g. springtails and oribatid mites) before expanding into most clades of terrestrial arthropods and filarial nematodes.

Combining time-resolved transcriptomics and proteomics data for Adverse Outcome Pathway refinement in ecotoxicology

Conventional Environmental Risk Assessment (ERA) of pesticide pollution is based on soil concentrations and apical endpoints, such as the reproduction of test organisms, but has traditionally disregarded information along the organismal response cascade leading to an adverse outcome. The Adverse Outcome Pathway (AOP) framework includes response information at any level of biological organization, providing opportunities to use intermediate responses as a predictive read-out for adverse outcomes instead. Transcriptomic and proteomic data can provide thousands of data points on the response to toxic exposure. Combining multiple omics data types is necessary for a comprehensive overview of the response cascade and, therefore, AOP development. However, it is unclear if transcript and protein responses are synchronized in time or time lagged. To understand if analysis of multi-omics data obtained at the same timepoint reveal one synchronized response cascade, we studied time-resolved shifts in gene transcript and protein abundance in the springtail Folsomia candida, a soil ecotoxicological model, after exposure to the neonicotinoid insecticide imidacloprid. We analyzed transcriptome and proteome data every 12 h up to 72 h after onset of exposure. The most pronounced shift in both transcript and protein abundances was observed after 48 h exposure. Moreover, cross-correlation analyses indicate that most genes displayed the highest correlation between transcript and protein abundances without a time-lag. This demonstrates that a combined analysis of transcriptomic and proteomic data from the same time-point can be used for AOP improvement. This data will promote the development of biomarkers for the presence of neonicotinoid insecticides or chemicals with a similar mechanism of action in soils.

Mismatches in thermal performance between ectothermic predators and prey alter interaction strength and top-down control

Climate change can alter predator-prey interactions when predators and prey have different thermal preferences as temperature change can exacerbate thermal mismatches (also called thermal asymmetry) with population-level consequences. We tested this using micro-arthropod predators (Stratiolaelaps scimitus) and prey (Folsomia candida) that differ in their temperature optima to examine predator-prey interactions across two temperature ranges, a cool (12 and 20 °C) and warm (20 and 26 °C) range. We predict that the lower thermal preference and optimum in F. candida will alter top-down control (i.e., interaction strength) by predators with interaction strength being strongest at intermediate temperatures, coinciding with F. candida thermal optimum. Predators and prey were placed in mesocosms, whereafter we measured population (predator and prey abundance), trait-based (average predator and prey body mass, and prey body length distribution), and predator-prey indices (predator-prey mass ratio (PPMR), Dynamic Index, and Log Response Ratio) to determine how temperature affected their interactions. Prey populations were the highest at intermediate temperatures (average temperature exposure: 16-23 °C) but declined at warmer temperatures (average temperature exposure: 24.5-26 °C). Predators consistently lowered prey abundances and average prey mass increased when predators were added. Top-down control was the greatest at intermediate temperatures (indicated by Log Response Ratio) when temperatures were near or below the thermal optimum for both species. Temperature-related prey declines negated top-down control under the warmest conditions suggesting that mismatches in thermal performance between predators and their prey will alter the strength and dominance of top-down or bottom-up forces of predator-prey interactions in a warmer world.

Evaluation of life-history traits in Folsomia candida exposed to combined repeated mild heat shocks with phenanthrene

Climate change increases the frequency and intensity of extreme weather events. In nature, organisms are often exposed to climatic stressors and contaminants simultaneously, and the effects of contaminants may be modified by climate change and vice versa. Here, the effects of repeated mild heat shocks (0-5 times, 30 °C for 6 h), alone or combined with phenanthrene (PHE) (80 mg kg^-1 dry soil), on life-history traits of the springtail Folsomia candida were investigated. The survival, growth, maturation, and reproduction of single juvenile springtails were assessed over a period of 37 days. Increasing number of heat bouts or PHE exposure did not have significant negative effects on overall survival at the termination of the experiment, but the interaction between the two stressors led to complex interactions for the dynamics of survival during the test. Neither body growth nor time to first oviposition was influenced by heat or PHE, but a reduction of egg production with increasing number of heat bouts was observed, and there was an interaction between the two stressors. Further, a trade-off between the number of eggs produced and egg size was observed, indicating that females invested the same amount of energy in reproduction despite exposure to stressful temperature and PHE. These results indicate that egg production (in terms of the number of eggs) was a more sensitive indicator of the combined effects of mild heat shocks and PHE than growth, and there was a trade-off between survival and egg production.

The interaction effects of biodegradable microplastics and Cd on Folsomia candida soil collembolan

In real-field soil conditions, multiple chemicals exposure may be the real scenario for soil biota. The co-occurrence of microplastics (MPs) and cadmium (Cd) is common in soils, which may pose a potential risk to soil ecosystems. Degradable microplastics are producing more MPs, and the potential effects on soil ecosystems are unknown. Therefore, a standard soil animal collembolan Folsomia candida was used to evaluate the single and interaction effects of biodegradable MPs (PLA) and Cd. The results showed that single and co-biodegradable PLA and Cd all had negative influences on the survival, reproduction, and growth of F. candida, and the effects intensified with PLA concentrations. The survival rate, reproduction rate, adult body length, and juvenile body length decreased by 20.0%, 24.2%, 22.9%, and 32.2% at MPs-100 treatment. But combined PLA and Cd alleviated the toxicity of single Cd on F. candida at lower PLA concentrations. The number of juveniles increased by 29.3%, the survival rate increased by 7.52%, the adult body length increased by 11.7%, and the juvenile body length increased by 19.0% at MPs-1 + Cd than single Cd treatment. Biochemical assays on antioxidant enzymes had the same results. Antioxidant enzymes CAT and POD were more sensitive than SOD. CAT and POD activities were induced quickly at shorter exposure periods, and MP treatment thus may be promising biomarkers on soil collembolan for soil MP exposure. PLA is degraded with time in soils; therefore, the long-term effects of co-MPs and Cd in soils are suggested to be further studied.

Ecotoxicological characterization of engineered biochars produced from different feedstock and temperatures

Biochar (BC) engineering, which has recently gained a lot of interest, allows designing the functional materials. BC modification improves the properties of pristine biochar, especially in terms of adsorption parameters. An interesting type of modification is the introduction of metals into the BC's structure. There is a knowledge gap regarding the effects of modified BC (e.g., BC-Mg, BC-Zn) on organisms. The aim of this study was the ecotoxicological evaluation of BC-Mg and BC-Zn composites, received under diverse conditions from willow or sewage sludge at 500 or 700 °C. The ecotoxicological tests with bacteria Vibrio fischeri (V. fischeri) and invertebrates Folsomia candida (F. candida) were applied to determine the toxicity of BC. The content of toxic substances (e.g., polycyclic aromatic hydrocarbons (PAHs), heavy metals (HMs), environmentally persistent free radicals (EPFRs)) in BC were also determined and compared with ecotoxicological parameters. The ecotoxicity of studied BCs depends on many variables: feedstock type, pyrolysis temperature and the modification type. The Zn and Mg modification reduced (from 28 to 63 %) the total Ʃ16 PAHs content in willow-derived BCs while in SL-derived BCs the total Ʃ16 PAHs content was even 1.5-3 times higher compared to pristine BCs. The Zn modified willow-derived BCs affected positively on F. candida reproduction but showed inhibition of luminescence V. fischeri. BC-Mg exhibited harmful effect to F. candida. The ecotoxicological assessment carried out sheds light on the potential toxicity of BC-Zn and BC-Mg composites, which are widely used in the removal of heavy metals, pharmaceuticals, dyes from waters and soils.

The Effects of Heavy Metal Pollution on Collembola in Urban Soils and Associated Recovery Using Biochar Remediation: A Review

Heavy metal pollution in urban soil continues to be a global issue that poses a serious hazard to invertebrates and human lives through oral ingestion and inhalation of soil particles. Though the toxicity of several heavy metals on invertebrates like Collembola has been studied, lead (Pb) and cadmium (Cd) have been extensively studied due to their high toxicity to collembolans. As a ubiquitous soil organism all over the world, collembolans have been used as a model species to study the effects of heavy metals on invertebrate communities. To reduce the effects of heavy metals on ecosystem functions, biotic and abiotic measures have been used for heavy metal remediation; biochar seems to be the most effective approach that not only increases the physical absorption of heavy metals but also indirectly benefits soil organisms. In this study, we briefly reviewed the application of biochar in Pb and Cd polluted soil and showed its potential in soil remediation. Furthermore, we outlined the potentially toxic effects of Pb- and Cd-polluted urban soil on the collembolan species. We searched peer-reviewed publications that investigated: (1) the level of Pb and Cd contamination on urban soil in different cities around the world; and (2) the different sources of Pb and Cd as well as factors influencing their toxicity to collembolan communities. The obtained information offers new perspectives on the interactions and effects between collembolans, Pb, and Cd, and their remediation in urban soils.

The use of sewage sludge as remediation for imidacloprid toxicity in soils

This study investigated the influence of the sewage sludge (SS) soil amendment on the chronic toxicity of imidacloprid (through the seed dressing formulation MUCH 600 FS®-600 g active ingredient L^-1) to collembolans Folsomia candida. Individuals 10-12 days old were exposed to two contrasting tropical soils (Oxisol and Entisol) amended with SS doses (0, 20, 40, 80, 160, and 320 g SS kg^-1 soil; the SS doses have low intrinsic toxicity, which was checked before its application) in a full factorial combination with five imidacloprid concentrations (varying from 0.25 to 4 mg kg^-1 in Oxisol and 0.03-0.5 mg kg^-1 in Entisol) plus a control. None of the SS doses (without imidacloprid) in both soils reduced the number of generated juvenile collembolans. The imidacloprid concentrations reducing the collembolan reproduction in 50% (EC₅₀) in Oxisol and Entisol without SS were 0.49 and 0.08 mg kg^-1, respectively. However, the EC₅₀ values generally increased with increasing SS doses in soils, varying from 1.03 to 1.41 in Oxisol and 0.07 to 0.21 in Entisol. The SS-amended soils showed 2.1- to 2.9-fold lower imidacloprid toxicity (EC₅₀-based) in Oxisol and 1.8- to 2.7-fold lower toxicity in Entisol. Our results suggest the most effective SS doses alleviating the imidacloprid toxicity (EC₅₀-based) to collembolans are 20 g kg^-1 in Oxisol and 80 g kg^-1 in Entisol. These results indicate that the tested SS has the potential to be employed as a soil amendment agent by reducing the toxicity of imidacloprid to the reproduction of F. candida.

Improved methods for quantifying soil invertebrates during ecotoxicological tests: Chill comas and anesthetics

Soil invertebrate ecotoxicological tests are important when making informed site-management decisions. However, traditional tests are time-consuming and require quantification of high numbers of soil invertebrates burrowed beneath the surface of soil. A commonly used technique to extract invertebrates from the soil is the floatation method. Due to the movement of Collembola, and the presence of small soil particulates and bubbles on the surface of the water, automatic image analysis software may inaccurately quantify the true number of individuals present. Hence, manual counting immediately following extraction, or from images, is still the most effective method utilized for quantifying floated soil invertebrates. This study investigated three novel techniques; the use of an ice-water bath, chest freezer (-12 °C) and ethanol to temporarily immobilize groups of 35 Folsomia candida individuals to increase accuracy during the quantification step. Active thermography to aid automatic image analysis was also investigated. Results show that while thermoimaging did not provide a distinct advantage in differentiating soil invertebrates from soil particles, both an ice-water bath and 4.75% ethanol solution were extremely effective at temporarily immobilizing F. candida with no apparent ill effects. The outcome of this study will assist future soil invertebrate research by increasing the accuracy of invertebrate quantifications. In addition, as the techniques caused no mortality to the invertebrates, the same individuals remain available for continuous monitoring experiments, repeated exposure, and/or multi-generational studies.

Heat stress delays detoxification of phenanthrene in the springtail Folsomia candida

Climate change has intensified the occurrence of heat waves, resulting in organisms being exposed to thermal and chemical stress at the same time. The effects of mild heat shock combined with sublethal concentrations of phenanthrene (PHE) on defense mechanisms in springtails Folsomia candida were investigated. The transcription of Heat Shock Protein 70 (HSP70) was significantly upregulated by heat shock but tended to reach the control levels after 42 h of recovery. The transcription of cytochrome P450 3A13 (CYP3A13) was upregulated 3-13 fold by PHE but suppressed by heat shock. The suppression by heat shock might contribute to the reduced detoxification of PHE during high-temperature exposure. In line with this, we found that the internal PHE concentration was approximately 70% higher in heat-shocked springtails than in animals kept at control temperature. In general, the transcription of genes encoding enzymes of detoxification phase Ⅱ (glutathione S-transferase 3) and phase Ⅲ (ABC transporter 1) and the activity of antioxidant defense enzymes (superoxide dismutase and catalase) were less influenced than genes encoding phase I detoxification mechanisms (CYP3A13). These results indicate that heat shock delays the detoxification of PHE in springtails.