The Impact of Environmental Mn Exposure on Insect Biology

Considering pollinators' ecosystem services in the remediation and restoration of contaminated lands: Overview of research and its gaps

The concept of ecosystem services provides a useful framework for understanding how people are affected by changes to the natural environment, such as when a contaminant is introduced (e.g., oil spills, hazardous substance releases) or, conversely, when contaminated lands are remediated and restored. Pollination is one example of an important ecosystem service; pollinators play a critical role in any functioning terrestrial ecosystem. Other studies have suggested that consideration of pollinators' ecosystem services could lead to better remediation and restoration outcomes. However, the associated relationships can be complex, and evaluation requires synthesis from numerous disciplines. In this article, we discuss the possibilities for considering pollinators and their ecosystem services when planning remediation and restoration of contaminated lands. To inform the discussion, we introduce a general conceptual model of how pollinators and the ecosystem services associated with them could be affected by contamination in the environment. We review the literature on the conceptual model components, including contaminant effects on pollinators and the direct and indirect ecosystem services provided by pollinators, and identify information gaps. Though increased public interest in pollinators likely reflects increasing recognition of their role in providing many important ecosystem services, our review indicates that many gaps in understanding-about relevant natural and social systems-currently impede the rigorous quantification and evaluation of pollinators' ecosystem services required for many applications, such as in the context of natural resource damage assessment. Notable gaps include information on non-honeybee pollinators and on ecosystem services beyond those benefitting the agricultural sector. We then discuss potential research priorities and implications for practitioners. Focused research attention on the areas highlighted in this review holds promise for increasing the possibilities for considering pollinators' ecosystem services in the remediation and restoration of contaminated lands. Integr Environ Assess Manag 2024;20:322-336. © 2023 SETAC.

Sugarcane vinasse provokes acute and chronic responses and bioaccumulation of metals in benthic macroinvertebrates

Brazil is a major producer of sugarcane bioethanol, which has raised concerns about its environmental impact. The industrial process for obtaining ethanol generates a by-product with a high pollution potential called vinasse. If vinasse reaches watercourses, it may affect the biological communities, such as the aquatic macroinvertebrates, which include species sensitive to environmental contamination. Thus, this study evaluated the ecotoxicological effects of sugarcane vinasse on tropical benthic macroinvertebrates (Allonais inaequalis, Chironomus sancticaroli, Strandesia trispinosa, and Hyalella meinerti). The study was divided into three phases. First, acute toxicity tests were carried out with the four species. The species A. inaequalis (average LC50 = 0.460% confidence interval, CI 0.380-0.540%) was more sensitive to vinasse than C. sancticaroli (LC50 0.721%, CI 0.565-0.878%), H. meinerti (EC50 0.781%, CI 0.637-0.925%), and S. trispinosa (EC50 1.283%, CI 1.045-1.522%). In the second phase, the consequences of chronic exposure to vinasse were assessed in the two more sensitive species. Impairments in reproduction and population growth rates for A. inaequalis and on the development, metamorphosis, and body growth of C. sancticaroli larvae occurred. Finally, the bioaccumulation of metals after chronic exposure was determined in the third phase. Vinasse provoked decreases in the body residue of the essential metals Zn and Mn and the accumulation of Cd, Pb, and Cr with the potential for biomagnification throughout the food webs. Low concentrations of vinasse (below 1%) provoked lethal and sublethal effects on benthic organisms, with several cascade effects on aquatic environments, given the ecological importance of this group in freshwater and terrestrial ecosystems.

Upcycling of recycled minerals from sewage sludge through black soldier fly larvae (Hermetia illucens): Impact on growth and mineral accumulation

Phosphorous (P) resources are finite. Sewage sludge recyclates (SSR) are not only of interest as plant fertilizer but also as potential source of minerals in animal nutrition. However, besides P and calcium (Ca), SSR contain heavy metals. Under EU legislation, the use of SSR derivatives in animal feed is not permitted, but given the need to improve nutrient recycling, it could be an environmentally sound future mineral source. Black soldier fly larvae (BSFL) convert low-grade biomass into valuable proteins and lipids, and accumulate minerals in their body. It was hypothesized that BSFL modify and increase their mineral content in response to feeding on SSR containing substrates. The objective was to evaluate the upcycling of minerals from SSR into agri-food nutrient cycles through BSFL. Growth, nutrient and mineral composition were compared in BSFL reared either on a modified Gainesville fly diet (FD) or on FD supplemented with either 4% of biochar (FD + BCH) or 3.6% of single-superphosphate (FD + SSP) recyclate (n = 6 BSFL rearing units/group). Larval mass, mineral and nutrient concentrations and yields were determined, and the bioaccumulation factor (BAF) was calculated. The FD + SSP substrate decreased specific growth rate and crude fat of BSFL (P < 0.05) compared to FD. The FD + SSP larvae had higher Ca and P contents and yields but the BAF for Ca was lowest. The FD + BCH larvae increased Ca, iron, cadmium and lead contents compared to FD. Larvae produced on FD + SSP showed lower lead and higher arsenic concentration than on FD + BCH. Frass of FD + BCH had higher heavy metal concentration than FD + SSP and FD (P < 0.05). Except for cadmium and manganese, the larval heavy metal concentration was below the legally permitted upper concentrations for feed. In conclusion, the SSR used could enrich BSFL with Ca and P but at the expense of growth. Due to the accumulation of Cd and Mn, BSFL or products thereof can only be a component of farmed animal feed whereas in BSFL frass heavy metal concentrations remained below the upper limit authorized by EU.

Study on phase evolution and promoting the pozzolanic activity of electrolytic manganese residue during calcination

Electrolytic manganese residue (EMR) is a harmful by-product in the electrolytic manganese industry. Calcination is an efficient method for disposing EMR. In this study, thermogravimetric-mass spectrometry (TG-MS) combined with X-ray diffraction (XRD) was used for analysing the thermal reactions and phase transitions during calcination. The pozzolanic activity of calcined EMR was determined by the potential hydraulicity test and strength activity index (SAI) test. The leaching characteristics of Mn were determined by TCLP test and BCR SE method. The results showed that MnSO₄ was converted into stable MnO₂ during calcination. Meanwhile, Mn-rich bustamite (Ca_0.228Mn_0.772SiO₃) was converted into Ca(Mn, Ca)Si₂O₆. The gypsum was transformed into anhydrite and then decomposed into CaO and SO₂. Additionally, the organic pollutants and ammonia were completely removed following calcination at 700 °C. The leaching concentration of Mn decreased from 819.9 mg L^-1 to 339.6 mg L^-1 following calcination at 1100 °C. The chemical forms of Mn were transformed from acid-soluble fraction to residual fraction. The pozzolanic activity tests indicated that EMR1100-Gy maintained a complete shape. The compressive strength of EMR1100-PO reached 33.83 MPa. Finally, the leaching concentrations of heavy metals met the standard limits. This study provides a better understanding for the treatment and utilization of EMR.

Metals and metal isotopes incorporation in insect wings: Implications for geolocation and pollution exposure

Anthropogenic activities are exposing insects to elevated levels of toxic metals and are altering the bioavailability of essential metals. Metals and metal isotopes have also become promising tools for the geolocation of migratory insects. Understanding the pathways of metal incorporation in insect tissues is thus important for assessing the role of metals in insect physiology and ecology and for the development of metals and metal isotopes as geolocation tools. We conducted a diet-switching experiment on monarch butterflies [Danaus plexippus (L.)] with controlled larval and adult diets to evaluate the sources of 23 metals and metalloids, strontium isotopes, and lead isotopes to insect wing tissues over a period of 8 weeks. Concentrations of Ca, Co, Mo, and Sb differed between the sexes or with body mass. Ni and Zn bioaccumulated in the insect wing tissues over time, likely from the adult diet, while increases in Al, Cr, Cd, Cu, Fe, and Pb were, at least partially, from external sources (i.e., dust aerosols). Bioaccumulation of Pb in the monarch wings was confirmed by Pb isotopes to mainly be sourced from external anthropogenic sources, revealing the potential of Pb isotopes to become an indicator and tracer of metal pollution exposure along migratory paths. Concentrations of Ba, Cs, Mg, Na, Rb, Sr, Ti, Tl, and U appeared to be unaffected by intrinsic factors or additions of metals from adult dietary or external sources, and their potential for geolocation should be further explored. Strontium isotope ratios remained indicative of the larval diet, at least in males, supporting its potential as a geolocation tool. However, the difference in strontium isotope ratios between sexes, as well as the possibility of external contamination by wetting, requires further investigation. Our results demonstrate the complexity of metal incorporation processes in insects and the value of studying metals to develop new tools to quantify pollution exposure, metal toxicity, micronutrient uptake, and insect mobility.

Probiotics as a promising prophylactic tool to reduce levels of toxic or potentially toxic elements in bees

Bees are precious living beings for our planet. Thanks to their essential service of pollination, these insects allow the maintenance of biodiversity and the variety and amount of food available. Unfortunately, we are observing an increasingly devastating reduction of bee families and other pollinating insects for factors related to human activities, environmental pollution, diseases and parasites, compromise of natural habitats, and climate change. We show that probiotics can protect bees from element pollution. We collected bees, beeswax, honey, pollen, and propolis directly from hives in a rural area of central Italy to investigate the content of 41 elements in control (not supplemented with probiotics) and experimental (supplemented with probiotics) groups. Our data show a significantly lower concentration of some elements (Ba, Be, Cd, Ce, Co, Cu, Pb, Sn, Tl, and U) in experimental bees than in control groups, indicating a possible beneficial effect of probiotics in reducing the absorption of chemicals. This study presents the first data on element levels after probiotics have been fed to bees and provides the basis for future research in several activities relating to the environment, agriculture, economy, territory, and medicine.

Behavioural regulation of mineral salt intake in honeybees: a self-selection approach

Minerals are required in small amounts to sustain metabolic activity in animals, but mineral deficiencies can also lead to metabolic bottlenecks and mineral excesses can induce toxicity. For these reasons, we could reasonably expect that micronutrients are actively regulated around nutritional optima. Honeybees have co-evolved with flowering plants such that their main sources of nutrients are floral pollen and nectar. Like other insects, honeybees balance their intake of multiple macronutrients during food consumption using a combination of pre- and post-ingestive mechanisms. How they regulate their intake of micronutrients using these mechanisms has rarely been studied. Using two-choice feeding assays, we tested whether caged and broodless young workers preferred solutions containing individual salts (NaCl, KCl, CaCl₂, MgCl₂) or metals (FeCl₃, CuCl₂, ZnCl₂, MnCl₂) in a concentration-dependent manner. We found that young adult workers could only self-select and optimize their dietary intake around specific concentrations of sodium, iron and copper. Bees largely avoided high concentration mineral solutions to minimize toxicity. These experiments demonstrate the limits of the regulation of intake of micronutrients in honeybees. This is the first study to compare this form of behaviour in one organism for eight different micronutrients. This article is part of the theme issue 'Natural processes influencing pollinator health: from chemistry to landscapes'.

Interactions and toxicity of non-essential heavy metals (Cd, Pb and Hg): lessons from Drosophila melanogaster

Some heavy metals are essential in trace amounts, enhancing enzyme functioning and other intracellular molecules. Others are explicitly toxic at low concentrations, increasing the risk of organ-related toxicity. Non-essential metals have similar mechanisms of toxicity to essential metals. These include the modifiable change in oxidation states, interaction with sulfhydryl moieties of proteins and indirect modification of nucleic acids. Ultimately, oxidative stress is generated, and potentiation of damage ensues. The susceptibility, sensitivity, genetic resources, and cellular response of Drosophila melanogaster to heavy metal exposure and toxicity have made this insect appropriate for toxicological studies. In this review, we focus on the toxicological impacts of non-essential metals (Cd, Pb, and Hg) in Drosophila and discuss its cellular and developmental responses to increasing concentrations of these metals. We also suggest current or proposed therapeutic alternatives, as well as dimensions that may improve the studies of non-essential metal biology.

Excessive manganese alters serum biochemical indices, induces histopathological alterations, and activates apoptosis in liver and cerebrum of Jianzhou Da'er goat (Capra hircus)

The present study aimed to explore the toxic effects of excessive dietary Mn in livers and cerebrums of Jianzhou Da'er goat (Capra hircus). Three-month old goats were assigned into three groups: control group, fed on basal diet; Mn I group, fed on the basal diet mixed with MnCl₂ (2.5 g/kg); Mn II group, fed on the basal diet mixed with MnCl₂ (5 g/kg). Compared with the control group, the activities of serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and the concentrations of interferon-γ (IFN-γ) in Mn I and Mn II groups were significantly increased, but the concentrations of IgG in Mn I and Mn II groups were significantly decreased (p < 0.05). The activities of superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and the concentrations of glutathione (GSH) in Mn I and Mn II groups were significantly decreased, whereas the concentrations of malondialdehyde (MDA) in Mn I and Mn II groups were significantly increased in livers and cerebrums (p < 0.05). Moreover, the hepatocytes necrosed, inflammatory cells infiltrated, chromatin concentrated, mitochondrial cristae reduced in Mn I and Mn II groups. The nerve cells necrosed, blood vessels congested, inflammatory cells infiltrated, mitochondrial electron density and mitochondrial cristae decreased, and vacuolization increased in Mn I and Mn II groups. Furthermore, the mRNA expressions of tumor necrosis factor alpha (TNF-α), tumor necrosis factor receptor type 1 (TNFR1), fas-associated protein via a death domain (FADD), Bcl2-associated X (Bax), cysteinyl aspartate specific proteinase 3, 8, 9 (Caspase-3, 8, 9) in Mn I and Mn II groups were significantly increased (p < 0.05), but the mRNA expressions of B-cell lymphoma-2 (Bcl-2) in Mn I and Mn II groups were significantly decreased (p < 0.05) in livers. The mRNA expressions of Bcl-2, Bax, Caspase-3, 9, 7, 12 in Mn I and Mn II groups were significantly increased (p < 0.05), however, the ratio of Bcl-2/Bax in Mn I and Mn II groups was significantly decreased (p < 0.05) in cerebrums. In summary, our results provided new insights for better understanding the mechanisms of Mn toxicity in Capra hircus.

Regulation and biological function of metal ions in Drosophila

A conceptual framework is offered for critically approaching the formidable ability of insects to segregate metal ions to their multiple destinations in proteins and subcellular compartments. New research in Drosophila melanogaster suggests that nuclear iron regulatory proteins and oxidative stress transcription factors mediate metal-responsive gene expression. Identification of a zinc-regulated chaperone in the endoplasmic reticulum potentially explains membrane protein trafficking defects observed in zinc transporter mutants. Compartmentalized zinc is utilized in fertilization, embryogenesis and for the activation of zinc-finger transcription factors - the latter function demonstrated during muscle development, while dietary zinc is sensed through gating of a chloride channel. Another emerging theme in cellular metal homeostasis is that transporters and related proteins meet at endoplasmic reticulum-mitochondria associated membranes with physiologically relevant consequences during aging.

Trophic transfer and toxicity of heavy metals from dengue mosquito Aedes aegypti to predator dragonfly Tramea cophysa

Heavy metal pollution in aquatic habitats can be detrimental to both prey and predators in a food web. To investigate the potential for bio-transfer and bioaccumulation of heavy metals between specific trophic levels, 3rd instar larvae of Aedes aegypti were exposed to mercury (Hg), lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) for three consecutive generations and fed to dragonfly (Tramea cophysa) nymphs. Exposure to Hg caused the highest mortality in A. aegypti larvae and T. cophysa nymphs. Bioaccumulation and life-history parameters of A. aegypti, including egg hatching time, larval and pupal duration, male and female life span, and fecundity, were also evaluated after metals exposure. All life-history parameters except larval duration were significantly affected by heavy metal treatments. Bioaccumulation of metals in A. aegypti larvae and adults gradually and significantly increased from 1st to 3rd generation. To the best of our knowledge, this is the first study describing the acute toxicity of heavy metals to mosquitoes. Our study shows that heavy metals cause dietary toxicity to an aquatic predator, dragonfly, via trophic transfer, which could have considerable consequences on aquatic ecosystems.

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.

How to Restore Invertebrate Diversity of Degraded Heathlands? A Case Study on the Reproductive Performance of the Field Cricket Gryllus campestris (L.)

Background

Nitrogen (NOx, NHy) and acidifying (NOx, NHy, SOx) deposition has reduced the biodiversity of European dry heathlands. Restoration efforts such as sod-cutting (removal of vegetation, litter and humus layer) often shifted these systems from N to P limitation and have had limited success in restoring the invertebrate community. Possible reasons for this include the unresolved acidification and a change in food plant stoichiometry. Here, we investigate how liming and P addition change food nutritional quality and their consequences for invertebrate performance.

Methods

We performed feeding experiments with field crickets (Gryllus campestris), using plant material collected from a full factorial field experiment with liming and P addition. We related female reproduction as measure of individual fitness to elemental ratios of plants fed to the crickets.

Results

P addition stimulated cricket daily reproduction and shortened their reproductive period, resulting in no difference in total reproduction. Liming greatly reduced both daily and total reproduction and resulted in more females cannibalizing on their male mates. Females that did so could partly offset the liming induced reduction in reproduction, suggesting dietary deficiency. P-addition improved food quality (lower N:P ratios) while liming led to skewed Mn:Mg and Fe:Mg ratios that compare unfavorably to ratios found in terrestrial invertebrates.

Conclusion

Increased plant N:P ratio following sod-cutting constrains the reproductive potential in Gryllus campestris in a non-linear way. Liming reduced nutritional quality, likely by inducing deficiencies in Fe or Mn.

Management Implications

High-impact restoration management practices such as sod cutting and liming cause new problems for invertebrates rooted in ecological stoichiometry. Since P-addition only partially offsets these negative effects, we instead advocate the use of less intensive N removal management and weaker buffering agents to reduce soil acidification. Furthermore, a reduction in N emission is paramount as it will remove the need for disruptive interventions.

Protective effect of gamma-oryzanol against manganese-induced toxicity in Drosophila melanogaster

Manganese (Mn) is an essential element that, in excess, seems to be involved in the development of different neurodegenerative conditions. Gamma-oryzanol (Ory) was previously reported to possess antioxidant and neuroprotective properties. Thus, we conducted this study to test the hypothesis that Ory can also protect flies in an Mn intoxication model. Adult wild-type flies were fed over 10 days with Mn (5 mM) and/or Ory (25 μM). Flies treated with Mn had a decrease in locomotor activity and a higher mortality rate compared to those in controls. Mn-treated flies also had a significant increase in acetylcholinesterase (AChE) activity, in Mn accumulation and in oxidative stress markers. Moreover, flies treated with Mn exhibited a significant decrease in dopamine levels and in tyrosine hydroxylase activity, as well as in mitochondrial and cellular viability. Particularly important, Ory protected against mortality and avoided locomotor and biochemical changes associated with Mn exposure. However, Ory did not prevent the accumulation of Mn. The present results support the notion that Ory effectively attenuates detrimental changes associated with Mn exposure in Drosophila melanogaster, reinforcing its neuroprotective action/potential.

Body Size Plasticity of Weevil Larvae (Curculio davidi) (Coleoptera: Curculionidae) and Its Stoichiometric Relationship With Different Hosts

Parasites obtain energy and nutrients from the host, and their body size is also usually limited by host size. However, the regulatory mechanisms that control the plasticity of parasite body sizes and the stoichiometric relationships with their hosts remain unclear. Here we investigated the concentrations of 14 elements (C, H, O, N, P, S, K, Na, Ca, Mg, Al, Fe, Mn, and Zn) in the acorns of three oak species (Quercus spp.), in their endoparasitic weevil (Curculio davidi Fairmaire) (Coleoptera: Curculionidae) larvae and in the larval feces, and the weight of weevil larvae within different hosts in a warm-temperate zone of China. Our results showed that the three acorn species exhibited significant differences in C, H, O, P, K, Mg, and Mn concentrations. However, in the weevil larvae, only P, Mn, and C:P ratio revealed significant differences. Weevil larvae preferentially absorbed and retained N, Zn, Na, and P, whereas Mn, K, Ca, and O were passively absorbed and transported. The weevil larvae weight was associated with acorn stoichiometry, and positively correlated with acorn size. Weevil larvae P decreased, but Mn and C:P increased with their weight, implying highly variable in somatic stoichiometry are coupled with the plasticity of body size. Interestingly, weevil larvae weight was negatively correlated with acorn infection rate, indicating small-size parasitic insects might have higher fitness level in parasite-host systems than larger-size ones. Our results suggest that variation in P, Mn, and C:P in parasites may play critical roles in shaping their body size and in improving their fitness.

Mineral Composition of Cereal and Cereal-Free Dry Dog Foods versus Nutritional Guidelines

The aims of the present work are to estimate the nutritional value and to evaluate and compare the levels of macroelements (Ca, P, K, Na, Mg), microelements (Fe, Zn, Mn, Cu), heavy metals (Co, Cd, Pb, Mo, Cr, Ni), and their ratios in extruded complete foods for adult dogs, their compatibility with nutritional guidelines, as well as food profile similarity. Basic composition was determined according to Association of Official Analytical Chemists (AOAC). Analyses for elements were performed using an atomic absorption spectrometer. All the evaluated dry dog foods met the minimum recommended levels for protein and fat. Eighteen tested dog foods (60%) did not meet at least one recommendation of nutritional guidelines. Four dog foods exceeded the legal limit of Fe and five foods exceeded the legal limit of Zn; in one of them, Zn level was almost twice higher. Dog foods with insect protein exceeded the legal limit for Mn content. Eight dog foods had an inappropriate Ca:P ratio. Heavy metals were below detection limit in all analyzed dog foods. The results seem to show the need for regular feed analyses of the elemental composition in raw materials before introducing supplementation and for the monitoring of the mineral composition of finished pet food.

Mineral analysis reveals extreme manganese concentrations in wild harvested and commercially available edible termites

Termites are widely used as a food resource, particularly in Africa and Asia. Markets for insects as food are also expanding worldwide. To inform the development of insect-based foods, we analysed selected minerals (Fe-Mn-Zn-Cu-Mg) in wild-harvested and commercially available termites. Mineral values were compared to selected commercially available insects. Alate termites, of the genera Macrotermes and Odontotermes, showed remarkably high manganese (Mn) content (292-515 mg/100 gdw), roughly 50-100 times the concentrations detected in other insects. Other mineral elements occur at moderate concentrations in all insects examined. On further examination, the Mn is located primarily in the abdomens of the Macrotermes subhyalinus; with scanning electron microscopy revealing small spherical structures highly enriched for Mn. We identify the fungus comb, of Macrotermes subhyanus, as a potential biological source of the high Mn concentrations. Consuming even small quantities of termite alates could exceed current upper recommended intakes for Mn in both adults and children. Given the widespread use of termites as food, a better understanding the sources, distribution and bio-availability of these high Mn concentrations in termite alates is needed.

Intestinal response to dietary manganese depletion inDrosophila

Metabolic adaptations to manganese deficiency.

Growth and Safety Assessment of Feed Streams for Black Soldier Fly Larvae: A Case Study with Aquaculture Sludge

The production of food is an intensive source of environmental impact. In aquaculture, one source of impact is solid waste, which contains high concentrations of minerals, other nutrients, and metals. The larvae of Hermetia illucens are capable of consuming this material, but applying technology that is based on these larvae for managing waste streams, like those from aquaculture, requires careful examination of safety risks. A study is performed examining the growth performance of larvae that were fed on solid aquaculture waste. Subsequently, a thorough analysis of safety risks from inorganics, with detailed the results on microelements that have previously received little attention in the literature, is performed to serve as a guideline for how to assess the safety of waste streams such as these. Findings confirm existing results in the literature that Cd is bioaccumulative, but also that other elements, including Hg, Mn, and especially K, are bioaccumulative. To the authors' knowledge, this is the first research where the accumulation of Ag is also tested. The results of these tests are explained within the context of regulations in various countries where Hermetia illucens is cultivated, serving as a reference for practitioners to rigorously screen out high risk feed streams that they may consider using as feed sources. It is intended that these references and the demonstrated accumulation of a range of elements motivate comprehensive industry safety practices when evaluating new feed sources.

Effects of ozone and ammonium sulfate on cauliflower: Emphasis on the interaction between plants and insect herbivores

Ammonium sulfate [(NH₄)₂SO₄] deposition and elevated ozone (O₃) concentrations may negatively affect plants and trophic interactions. This study aimed to evaluate for the first time the interactive effects of high (NH₄)₂SO₄ load and elevated O₃ levels on cauliflower (Brassica oleracea L.) under field conditions. Cauliflower seedlings were treated with 0 (AS0) or 50 (AS50) kg ha^-1 (NH₄)₂SO₄ and exposed to ambient (AOZ, ≈20 ppb) or elevated (EOZ, ≈55 ppb) O₃ for about one month, in a Free Air O₃ Concentration Enrichment (FACE) system. The oligophagous diamondback moth (Plutella xylostella Linnaeus, 1758) showed a clear preference towards the seedlings treated with AS50, which intensively grazed. Plant-herbivore interactions were driven by (NH₄)₂SO₄ availability, rather than O₃, via increased nitrogen content in the leaves. Further laboratory bioassays were followed to confirm the validity of these observations using polyphagous Eri silkmoth larvae (Samia ricini) as a biological model in a standardized experimental setup. Choice assays, where larvae could select leaves among leaf samples from the different experimental conditions, and no-choice assays, where larvae could graze leaves from just one experimental condition, were conducted. In the choice assay, the larvae preferred AS50-treated leaves, in agreement with the field observations with diamondback moth. In the no-choice assay, larval body mass growth was inhibited when fed with leaves treated with EOZ and/or AS50. Larvae fed with AS50-treated leaves displayed increased mortality. These observations coincide with higher NO₃ and Zn content in AS50-treated leaves. This study shows that plant-herbivore interactions can be driven by (NH₄)₂SO₄ availability, independently of O₃, and suggests that high N deposition may have severe health implications in animals consuming such plant tissues. Key message: Plant-herbivore interactions are driven by high (NH₄)₂SO₄ availability, independently of O₃.

The Role of Heavy Metals in Plant Response to Biotic Stress

The present review discusses the impact of heavy metals on the growth of plants at different concentrations, paying particular attention to the hormesis effect. Within the past decade, study of the hormesis phenomenon has generated considerable interest because it was considered not only in the framework of plant growth stimulation but also as an adaptive response of plants to a low level of stress which in turn can play an important role in their responses to other stress factors. In this review, we focused on the defence mechanisms of plants as a response to different metal ion doses and during the crosstalk between metal ions and biotic stressors such as insects and pathogenic fungi. Issues relating to metal ion acquisition and ion homeostasis that may be essential for the survival of plants, pathogens and herbivores competing in the same environment were highlighted. Besides, the influence of heavy metals on insects, especially aphids and pathogenic fungi, was shown. Our intention was also to shed light on the relationship between heavy metals deposition in the environment and ecological communities formed under a strong selective pressure.