Localization of metals in cells of pterygote insects

Exploring the effects of the acaricide cyflumetofen on the vital organs of the honey bee Apis mellifera (Hymenoptera: Apidae) workers

Bees are important for maintaining ecosystems, pollinating crops and producing marketable products. In recent years, a decline in bee populations has been reported, with multifactorial causes, including the intensification of pesticide use in agriculture. Among pesticides, cyflumetofen is an insecticide and acaricide used in apple, coffee and citrus crops, whose main pollinator is the honey bee Apis mellifera. Therefore, this bee is a potential target of cyflumetofen during foraging. This study evaluated the histopathological and cytological damage in the midgut, hypopharyngeal glands and fat body of A. mellifera workers exposed to LC50 of cyflumetofen. The midgut epithelium of exposed bees presented cytoplasmic vacuolization, release of vesicles and cell fragments, which indicate autophagy, increased production of digestive enzymes and cell death, respectively. The cytological analysis of the midgut revealed the dilation of the basal labyrinth and the presence of spherocrystals in the digestive cells. The hypopharyngeal glands produced greater amounts of secretion in treated bees, whereas no changes were observed in the fat body. The results indicate that acute exposure to cyflumetofen negatively affect A. mellifera, causing damage to the midgut and changes in the hypopharyngeal glands, which may compromise the survival and foraging of this pollinator.

Molecular strategies of the pygmy grasshopper Eucriotettix oculatus adapting to long-term heavy metal pollution

To study the heavy metal accumulation and its impact on insect exterior and chromosome morphology, and reveal the molecular mechanism of insects adapting to long-term heavy metal compound pollution habitats, this study, in the Diaojiang river basin, which has been polluted by heavy metals(HMs) for nearly a thousand years, two Eucriotettix oculatus populations was collected from mining and non-mining areas. It was found that the contents of 7 heavy metals (As, Cd, Pb, Zn, Cu, Sn, Sb) in E. oculatus of the mining area were higher than that in the non-mining 1-11 times. The analysis of morphology shows that the external morphology, the hind wing type and the chromosomal morphology of E. oculatus are significant differences between the two populations. Based on the heavy metal accumulation，morphological change, and stable population density, it is inferred that the mining area population has been affected by heavy metals and has adapted to the environment of heavy metals pollution. Then, by analyzing the transcriptome of the two populations, it was found that the digestion, immunity, excretion, endocrine, nerve, circulation, reproductive and other systems and lysosomes, endoplasmic reticulum and other cell structure-related gene expression were suppressed. This shows that the functions of the above-mentioned related systems of E. oculatus are inhibited by heavy metal stress. However, it has also been found that through the significant up-regulation of genes related to the above system, such as ATP2B, pepsin A, ubiquitin, AQP1, ACOX, ATPeV0A, SEC61A, CANX, ALDH7A1, DLD, aceE, Hsp40, and catalase, etc., and the down-regulation of MAPK signalling pathway genes, can enhanced nutrient absorption, improve energy metabolism, repair damaged cells and degrade abnormal proteins, maintain the stability of cells and systems, and resist heavy metal damage so that E. oculatus can adapt to the environment of heavy metal pollution for a long time.

Management of inorganic elements by overwintering physiology of cold hardy larvae of European corn borer (Ostrinia nubilalis, Hbn.)

The European corn borer (Ostrinia nubilalis, Hbn.), enters diapause, a strategy characterized by arrest of development and reproduction, reduction of metabolic rate and the emergence of increased resistance to challenging seasonal conditions as low sub-zero winter temperatures. The aim of this study was to investigate the potential role of inorganic elements in the ecophysiology of O. nubilalis, analysing their content in the whole body, hemolymph and fat body, both metabolically active, non-diapausing and overwintering diapausing larvae by ICP-OES spectrometer following the US EPA method 200.7:2001. O nubilalis as many phytophagous lepidopteran species maintain a very low extracellular sodium concentration and has potassium as dominant cation in hemolymph of their larvae. Changes in hemolymph and the whole body sodium content occur already at the onset of diapause (when the mean environmental temperatures are still high above 0 ºC) and remain stable during the time course of diapause when larvae of this species cope with sub-zero temperatures, it seems that sodium content regulation is rather a part of diapausing program than the direct effect of exposure to low temperatures. Compared to non-diapausing O. nubilalis larvae, potassium levels are much higher in the whole body and fat body of diapausing larvae and substantially increase approaching the end of diapause. The concentration of Ca, Mg, P and S differed in the whole body, hemolymph and fat body between non-diapausing and diapausing larvae without a unique trend during diapause, except an increase in their contents at the end of diapause.

Dietary calcium (Ca2+) impacts Ca2+ content and molecular expression of Ca2+-transporters in Malpighian tubules of the yellow fever mosquito, Aedes aegypti

The renal (Malpighian) tubules of insects play important roles in hemolymph Ca2+ regulation. Here we investigated how dietary Ca2+ loads from sucrose or blood meals affect the Ca2+ content and mRNA expression of Ca2+ transporters in Malpighian tubules of adult female mosquitoes. Using the yellow fever mosquito Aedes aegypti we found that feeding females 10% sucrose with elevated Ca2+ concentration ad libitum for 6 days led to increased Ca2+ content in Malpighian tubules. The increases of Ca2+ content correlated with up-regulations of mRNAs encoding intracellular Ca2+-ATPases (SERCA and SPCA), a plasma membrane Ca2+-ATPase (PMCA), and a K+-dependent Na+/Ca2+ exchanger (NCKX1). We also found that when adult females were fed blood, tubule Ca2+ content changed dynamically over the next 72 h in a manner consistent with redistribution of tubule Ca2+ stores to other tissues (e.g., ovaries). The changes in tubule Ca2+ were correlated with dynamic changes in mRNA abundances of SERCA, SPCA, PMCA, and NCKX1. Our results are the first to demonstrate that Malpighian tubules of adult female mosquitoes have a remarkable capacity to handle high dietary Ca2+ loads, most likely through the combination of storing excess Ca2+ within intracellular compartments and secreting it into the tubule lumen for excretion. Our results also suggest that the Malpighian tubules play key roles in supplying Ca2+ to other tissues during the processing of blood meals.

Biosynthesized silver nanoparticles (Ag NPs) from isolated actinomycetes strains and their impact on the black cutworm, Agrotis ipsilon

Nanomaterials have been produced with the use of bio-nanotechnology, which is a low-cost approach. Currently, research is being conducted to determine whether actinomycetes isolated from Egyptian soil can biosynthesize Ag nanoparticles (Ag NPs) and characterized by using the following techniques: Transmission electron microscopy (TEM), Dynamic light scattering (DLS), Fourier transforms infrared (FT-IR), Energy-dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy and X-ray diffraction (XRD). The most promising actinomycetes isolate were identified, morphologically, biochemically, and molecularly. Streptomyces avermitilis Azhar A.4 was found to be able to reduce silver metal nanoparticles from silver nitrate in nine isolates collected from Egyptian soil. Toxicity of biosynthesized against 2nd and 4th larval instar of Agrotis ipsilon (Hufn.) (Lepidoptera: Noctuidae) was estimated. In addition, activity of certain vital antioxidant and detoxifying enzymes as well as midgut histology of treated larvae were also investigated. The results showed appositive correlations between larval mortality percentage (y) and bio-AgNPs concentrations (x) with excellent (R2). The 4th larval instar was more susceptible than 2nd larval instar with LC50 (with 95% confirmed limits) =8.61 (2.76-13.89) and 26.44(13.25-35.58) ppml-1, respectively of 5 days from treatment. The initial stages of biosynthesized AgNps exposure showed significant increases in carboxylesterase (CarE) and peroxidases (PODs) activity followed by significant suppression after 5 days pos-exposure. While protease activity was significantly decreased by increasing time post-exposure. Midgut histology showed abnormality and progressive damage by increasing time post exposure leading to complete destruction of midgut cells after 5 days from exposure. These results make biosynthesized AgNPs an appropriate alternative to chemical insecticide in A. ipsilon management.

Calcium storage in Malpighian tubules and the putative use for pupal chamber formation in a wood-feeding insect

Cerambycid beetles form a chamber to spend their pupal stages in various forms according to the species. The red-necked longhorn beetle Aromia bungii (Coleoptera: Cerambycidae), which is an invasive pest that severely damages Rosaceae trees, makes a pupal chamber at the end of a tunnel deep in the xylem. Beetle larvae and the closely related species form a calcareous lid at the entrance of a pupal chamber. Previous studies on the closely related species conducted more than century ago suggested that Malpighian tubules (MTs) play a vital role in calcium carbonate accumulation. However, the association between this Ca²⁺ accumulation and pupal chamber lid formation utilizing the possible calcium compounds stored in MTs have not yet been demonstrated. First, we artificially reared A. bungii larvae from eggs in host branches for 100 days and identified the larval developmental status and pupal chamber formation, using X-ray computed tomography. Second, we collected larvae from the branches and observed the internal organs by direct dissection under a microscope. Finally, we analyzed the elemental distribution, particularly calcium, in the larval gut with MTs, using energy dispersive X-ray fluorescence. The results suggest that immature larvae of A. bungii could accumulate Ca²⁺ in the MTs through wood tunneling and feeding activities. Ca²⁺ was stored at the proximal regions in two of the six MTs located posteriorly in the body. Additionally, larvae that formed a calcareous lid at the entrance of pupal chambers in the branches did not store Ca²⁺ in the MTs, suggesting that the larvae of A. bungii used the stored Ca²⁺ in their MTs for lid formation.

Triazine Herbicide and NPK Fertilizer Exposure: Accumulation of Heavy Metals and Rare Earth Elements, Effects on Cuticle Melanization, and Immunocompetence in the Model Species Tenebrio molitor

The increasing use of agrochemicals, including fertilizers and herbicides, has led to worrying metal contamination of soils and waters and raises serious questions about the effects of their transfer to different levels of the trophic web. Accumulation and biomagnification of essential (K, Na, Mg, Zn, Ca), nonessential (Sr, Hg, Rb, Ba, Se, Cd, Cr, Pb, As), and rare earth elements (REEs) were investigated in newly emerged adults of Tenebrio molitor exposed to field-admitted concentrations of a metribuzin-based herbicide and an NPK blend fertilizer. Chemical analyses were performed using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) supported by unsupervised pattern recognition techniques. Physiological parameters such as cuticle melanization, cellular (circulating hemocytes), and humoral (phenoloxidase enzyme activity) immune responses and mass loss were tested as exposure markers in both sexes. The results showed that NPK fertilizer application is the main cause of REE accumulation in beetles over time, besides toxic elements (Sr, Hg, Cr, Rb, Ba, Ni, Al, V, U) also present in the herbicide-treated beetles. The biomagnification of Cu and Zn suggested a high potential for food web transfer in agroecosystems. Gender differences in element concentrations suggested that males and females differ in element uptake and excretion. Differences in phenotypic traits show that exposure affects metabolic pathways involving sequestration and detoxification during the transition phase from immature-to-mature beetles, triggering a redistribution of resources between sexual maturation and immune responses. Our findings highlight the importance of setting limits for metals and REEs in herbicides and fertilizers to avoid adverse effects on species that provide ecosystem services and contribute to soil health in agroecosystems.

Mobile samplers of particulate matter - Flying omnivorous insects in detection of industrial contamination

Flying insects are potential mobile samplers of airborne particulate matter (PM). However, current knowledge on their susceptibility to PM is limited to pollinators. Insects' capacity for particle surface accumulation depends on the lifestyle, structure of the body integuments, and behavioral patterns. Here, we investigate how two species of flying omnivorous insects from the genus Vespula, possessing direct interactions with air, soil, plants, and herbivores, indicate industrial pollution by accumulating coarse (PM₁₀) and fine (PM_2.5) particles on their bodies. The internal accumulation of particles in wasps' gut tissues is assessed considering heavy metals exposure to reveal and discuss the potential magnitude of ecotoxicological risks. Female individuals of Vespula vulgaris and V. germanica were sampled with a hand-netting near to Harjavalta Cu-Ni smelter and in the control areas in southwestern Finland. They were analyzed with light microscopy (LM), electron microscopy (SEM, TEM), and energy-dispersive X-ray spectroscopy (EDX) methods. Near to the smelter, wasps trapped significantly more particles, which were of bigger size and their surface optical density was higher. Vespula vulgaris accumulated larger particles than V. germanica, but that wasn't associated with morphological characteristics such as body size or hairiness. In both areas, accumulated surface PM carried clays and silicates. Only in polluted environments PM consistently contained metallic and nonmetallic particles (from high to moderate weight %) of Fe, Ni, Cu, and S - major pollutants emitted from the smelter. Wasps from industrially polluted areas carried significantly more granules in the columnar epithelial midgut cells. TEM-EDX analyses identified those structures were associated with metal ions such as Cr, Cu, Ni, and Fe. As epithelial gut cells accumulated metal particles, midgut confirmed as a barrier for metal exposure in wasps. External PM contamination in wasps is suggested as a qualitative, yet a natural and simple descriptor of local industrial emissions.

Fine structure of the posterior midgut in the mite Anystis baccarum (L.)

Homology of the posterior midgut regions (PMG) in different phylogenetic lineages of acariform mites (superorder Acariformes) remains unresolved. In the order Trombidiformes, the ultrastructure of the PMG is known primarily in derived groups; thus this study focuses on species belonging to a relatively basal trombidiform family. PMG of Anystis baccarum consists of the colon and postcolon separated by a small intercolon. The fine structure of the colon and postcolon is close to that of the corresponding organs of sarcoptiform mites with the epithelium showing absorptive and endocytotic activity. The epithelial cells produce a variety of excretory vacuoles and a peritrophic matrix around the feces. Morover, the epithelium of the postcolon is characterized by the highest apical brush border and especially numerous mitochondria suggesting involvement in water and ion absorption. The intercolon functions as a sphincter lined with an epithelium capable of producing excretory granules. A pair of short blind extensions arises assimmetrically from the intercolon into the body cavity. Ultrastructurally, these extensions are similar to the arachnid Malpighian tubules and may be their reduced version. Rare endocrine-like cells have been observed in the colon and postcolon.

Migration and Transformation of Cd in Pig Manure-Insect Frass (Hermetia illucens)-Soil-Maize System

Little is known about the fate of heavy metals in the recycling system of animal manure-black soldier fly larvae (BSFL) transformation-larval frass application. In this work, BSFL-transformed pig manure with different concentrations of exogenous cadmium (Cd) (0, 3, 15, 30 mg kg^-1), and the obtained BSFL frass fertilizer were further used in pot experiments of maize planting to explore Cd migration during the whole recycling system. Results showed that Cd addition to pig manure had no significant effects on BSFL growth or BSFL transformation performance. The Cd concentrations in BSFL frass were 10.9-19.8% lower than those in pig manure, while those in BSFL bodies were 2.3-4.0-times those of pig manure. For maize planting, only 30 mg kg^-1 of Cd treatment significantly inhibited maize growth. The BSFL frass application (under exogenous Cd treatment) enhanced Cd contents in the aboveground and underground parts of maize (3.3-57.6-times) and those in soil (0.5-1.7-times) compared with CK (no Cd addition). Additionally, 61.2-73.5% of pig manure-sourced Cd was transformed into BSFL frass and the rest entered BSFL bodies. Only a small part (0.31-1.34%) of manure-sourced Cd entered maize plants. BSFL transformation decreased the proportions of weak acid-dissolved Cd from 44.2-53.0% (manure) to 37.3-46.0% (frass). After frass application, the proportions of weak acid-dissolved Cd in soil were further decreased to 17.8-42.5%, while the residual fractions of Cd increased to 27.2-67.7%. The findings provided a theoretical basis for the rational application of BSFL frass fertilizers sourced from heavy-metal-contaminated manure.

Larvicidal and Antifeedant Effects of Copper Nano-Pesticides against Spodoptera frugiperda (J.E. Smith) and Its Immunological Response

This study aimed to synthesize and evaluate the efficacy of CuO NPs (copper oxide nanoparticles) with varying test concentrations (10−500 ppm) against larvicidal, antifeedant, immunological, and enzymatic activities against larvae of S. frugiperda at 24 h of treatment. Copper nanoparticles were characterized by using a scanning electron microscope (SEM) and energy dispersive X-ray (EDaX) analysis. The EDaX analysis results clearly show that the synthesized copper nanoparticles contain copper as the main element, and the SEM analysis results show nanoparticle sizes ranging from 29 to 45 nm. The CuO NPs showed remarkable larvicidal activity (97%, 94%, and 81% were observed on the 3rd, 4th, and 5th instar larvae, respectively). The CuO NPs produced high antifeedant activity (98.25%, 98.01%, and 98.42%), which was observed on the 3rd, 4th, and 5th instar larvae, respectively. CuO NPs treatment significantly reduced larval hemocyte levels 24 h after treatment; hemocyte counts and sizes changed in the CuO NPs treatment compared to the control. After 24 h of treatment with CuO NPs, the larval acetylcholinesterase enzyme levels decreased with dose-dependent activity. The present findings conclude that CuO NPs cause remarkable larvicidal antifeedant activity and that CuO NPs are effective, pollution-free green nano-insecticides against S. frugiperda.

Exposure to High Concentrations of Cadmium Which Delay Development of Ostrinia Nubilalis Hbn. Larvae Affected the Balance of Bioelements

All processes involved in metal homeostasis must be coordinated to provide sufficient, but not toxic, concentrations of important bioelements, and to minimize detrimental effects of toxic metals. Our previous studies dealing with the exposure of O. nubilalis non-diapausing larvae to dietary Cd demonstrated that exposure to higher concentrations of Cd caused delay in the development of larvae, induced oxidative stress and also induced defense mechanisms against the toxic effects of Cd. The aim of the present study was to evaluate how acute and chronic exposure of O. nubilalis larvae to increased concentrations of dietary Cd affected the balance of important bioelements. The concentration of bioelements was analyzed in larvae (after short-term exposure) and pupae (after long-term exposure). The short-term exposure of final instar larvae (L5) to Cd did not affect significantly the concentration of any of the analyzed bioelements, while the long-term exposure of developing larvae to higher concentrations of Cd caused increase in the concentrations of Ca, Mg and Na in pupae. The bioaccumulation factor, calculated for bioelements after long-term exposure to Cd, was higher for the most bioelements in groups fed with diet containing higher concentrations of Cd, except K which displayed the opposite trend. Pearson correlation coefficient showed positive correlations between Cd and Ca, Mg, Na, Fe, Cu and Zn, while negative correlation was observed between Cd and K. The results indicate that impact on the balance of important bioelements might be one of the mechanisms of cadmium toxicity and certainly raise numerous questions for future research.

Zinc supplementation modifies brain tissue transcriptome of Apis mellifera honeybees

BACKGROUND

Bees are the most important group of pollinators worldwide and their populations are declining. In natural conditions, Apis mellifera depends exclusively on food from the field to meet its physiological demands. In the period of scarcity, available resources are insufficient and artificial supplementation becomes essential for maintaining the levels of vitamins, proteins, carbohydrates, and minerals of colonies. Among these minerals, zinc is essential in all living systems, particularly for the regulation of cell division and protein synthesis, and is a component of more than 200 metalloenzymes.

RESULTS

The total RNA extracted from the brain tissue of nurse bees exposed to different sources and concentrations of zinc was sequenced. A total of 1,172 genes in the treatment that received an inorganic source of zinc and 502 genes that received an organic source of zinc were found to be differentially expressed among the control group. Gene ontology enrichment showed that zinc can modulate important biological processes such as nutrient metabolism and the molting process.

CONCLUSIONS

Our results indicate that zinc supplementation modulates the expression of many differentially expressed genes and plays an important role in the development of Apis mellifera bees. All the information obtained in this study can contribute to future research in the field of bee nutrigenomics.

Photochemical effect of silver nanoparticles on flesh fly larval biological system

With the progress of nanoscience and its applications, silver nanoparticles (AgNPs) have become one of the most interesting nanoparticles owing to their use in different fields. However, the excessive use of AgNPs and its products may cause toxicity in both the environment and in human health. The main goal of this research is to study the toxic and photochemical effects of AgNPs against Sarcophaga argyrostoma larvae through ultrastructure, morphological change, and DNA damage. Treating midgut epithelium with AgNPs led to many alterations in dark conditions, disintegrated epithelium, swollen cells, and shrunken nucleus. Organelles appeared in a loose manner and mitochondria were without cristae, endoplasmic reticulum had dark spots, and peritrophic membrane was loose in appearance. Fatty tissues were vacuolized and muscle fibers lacked normal striations and had many gaps and lysosomal bodies. In the light conditions, the epithelium appeared with detached cells and many vacuoles, organelles were ruptured with many gaps in between, and secretory vesicles were scattered. Peritrophic membrane disappeared. Muscles collapsed and vacuolized loosed fatty tissues were detected. On the other hand, control larvae epithelium appeared regularly distinct, with organelles intact and muscles had clear normal striations. Data showed that AgNPs caused ultrastructural and morphological changes of the external cuticle of the 4th instar larvae along with a significant effect on DNA damage that occurred after the larval treatment, reflecting the toxicity of AgNPs.

Genetics of metallothioneins in Drosophilamelanogaster

Metallothioneins (MTs) are ubiquitous metal-chelating proteins involved in cellular metal homeostasis. MTs were found to be related with almost all the biological processes and their malfunctioning is responsible for a lot of important human diseases. Invertebrate MTs were also used broadly as biomarkers of metal contamination due to their inducible expression by metal exposure. MT system plays a significant role in maintaining human health and ecological stability. Drosophila melanogaster, the vinegar fly, is a perfect model for studying insect MT systems. Six MTs were identified in D. melanogaster, and were designated MtnA to F. All the MTs are considered as Cu-thioneins except for MtnF, which is putatively a Zn-thionein. Expression of all the MTs are regulated by MTF-1/MRE system, thus being able to be induced by heavy metal exposure. The expression pattern and function of separated MTs are partially overlapped and partially distinct. In this work, we made a summary of all the studies on D. melanogaster MTs. From this review, we noted that, compared with studies on mammalian MTs, the understanding of the MT system of D. melanogaster and other invertebrates, especially the regulation mechanism for MT expression and protein-protein interaction with them, is still in a low level.

Gene expression profiles in Malpighian tubules of the vector leafhopper Psammotettix striatus (L.) revealed regional functional diversity and heterogeneity

Background

Many leafhoppers are known as pests and disease vectors of economically important plants. Previous studies of the physiological functions of vector leafhoppers have mainly focused on the salivary glands and the alimentary tract that are deemed to be associated with digestion, host defense and phytoplasma and/or virus transmission. By contrast, the significance of Malpighian tubules (MTs) is less studied. To clarify the physiological function of MTs of the vector leafhopper Psammotettix striatus that transmits phytoplasma triggering the wheat blue dwarf disease, we performed a transcriptome study on P. striatus MTs and compared gene expression profiles among different anatomical regions in the tubules (i.e., MT1+2, the anterior segment together with the sub-anterior segment; MT3, the inflated segment; and MT4, the distal segment).

Results

Transcriptome of P. striatus MTs generate a total of 42,815 high-quality unigenes, among which highly expressed unigenes are mainly involved in organic solute transport, detoxification and immunity in addition to osmoregulation. Region-specific comparative analyses reveal that all these MT regions have functions in osmoregulation, organic solute transport and detoxification, but each region targets different substrates. Differential expression and regional enrichment of immunity-related effector activities and molecules involved in phagocytosis and the biosynthesis of antimicrobial peptides among different regions indicate that MT1+2 and MT4 have the ability to eliminate the invading pathogens. However, in MT3 which secrets brochosomes to the integument and eggs as physical barriers, disulfide-isomerase, acidic ribosomal protein P and many other unigenes were highly expressed, which can be attractive candidate genes for future studies of the biosynthesis and the origin of brochosomes.

Conclusions

Psammotettix striatus MTs perform multiple physiological functions as versatile organs than just excretory organs with osmoregulatory function. Heterogeneity of physiological functions among different MT regions is related to organic solute transport, detoxification, immunity and brochosome biosynthesis in addition to osmoregulation, and each region targets different substrates. These functions may be helpful for P. striatus to resist pathogens from habitats and to utilize a wider range of host plants, which may assist the transmission and spread of phytoplasmas. The results provide potential molecular targets for the exploit of chemical and/or gene-silencing insecticides.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08300-6.

Ultrastructure of spherites in the midgut diverticula and Malpighian tubules of the harvestman Amilenus aurantiacus during the winter diapause

Amilenus aurantiacus overwinter in diapause, a natural starvation period, in hypogean habitats. The structure of spherites in the midgut diverticula (MD) and Malpighian tubules (MT) has been studied comparatively by light microscopy and TEM to detect eventual differences in mineral consumption in the beginning and at the end of the starvation period in these organs (MD and MT) associated with digestive processes. The chemical composition of spherites was examined by combining energy-dispersive X-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS) and energy-filtered TEM (EFTEM). The structure of the spherites changed during overwintering in both organs. At the beginning of overwintering, the spherites were composed of densely packed concentric layers of electron-dense and electron-lucent material. In the middle and at the end of overwintering, the electron-lucent layers between the layers of material indicated the loss of some material. The chemical composition of the spherites changed only in the MD; at the beginning of overwintering, these contained Si, O, C and Fe, while later there was no more Fe. In contrast, spherites in the MT were composed of Si, O, C and Ca throughout overwintering. A less intensive exploitation of the MD spherites was probably due to complete cessation of digestive and other cell activity in this organ during the winter diapause; activity of the MT slowed, but continued removing the cell metabolites.

Heavy Metals Accumulation in Dragonflies (Odonata) and Their Habitats in District Swabi, Khyber Pakhtunkhwa, Pakistan: Assessing Dragonfly Bionomics in the Region

The current study aimed to examine the bionomics of dragonflies and heavy metal accumulation in their bodies and environment (sediments and water) from district Swabi, Khyber Pakhtunkhwa, Pakistan. A total of 1683 dragonflies were collected from May to September, 2018 in 4 tehsils (administrative subdivisions) of district. Orthetrum pruinosum neglectum was the most abundant species followed by O. anceps and O. chrysostigma luzonicum. Highest abundance was observed in July and August corresponding to maximum temperature and rainfall. Dragonflies displayed preferable abundance within agricultural lands and on elevation ranging from 206 to 506 m. Heavy metal analysis of sediments and water samples from 4 tehsils showed significant differences in mean concentrations of Pb, Zn, Cu, and Fe. Abundance among districts was negatively associated with Fe levels in water while the species diversity had a significant positive relationship with Fe in sediments. Accumulation of metals in each body part significantly varied among species. N. tullia tullia and O. anceps specifically demonstrated their tolerance to high concentrations of heavy metals.

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

Simple Summary

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

Abstract

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

Copper and zinc impact on stress biomarkers and growth parameters in a model organism, Galleria mellonella larvae

The objective of the present study was to investigate the impact of zinc and copper on some biomarkers in a model organism Galleria mellonella L. We investigated the effects of Cu and Zn (10, 50, and 100 mg/100 g diets) on different biomarkers such as oxidative stress parameters (SOD and CAT activities and MDA levels), energy resources (protein, lipid and glycogen levels), electrolyte contents (Ca, Na, and K levels), total hemocyte count (THC), and growth and development of G. mellonella. Additionally, the accumulation levels of the used metals were also studied. Cu caused a significant decrease in protein, lipid and glycogen levels. SOD and CAT activities significantly increased at all concentrations of Cu, while they significantly increased at only high concentrations of Zn (50 and 100 mg). Lipid peroxidation levels (MDA) significantly elevated at high concentrations of both metals. It was determined that the Cu and Zn accumulation increased depending on the increase of the concentration. Zn caused an alteration in Ca level at the concentrations of 50 and 100 mg, and K and Na levels at all concentrations. While, THC significantly reduced at all Cu concentrations, this reduction was observed only at higher Zn concentrations (50 and 100 mg). Larval and pupal development time significantly extended at the highest concentration (100 mg) of Cu, and females' lifespan significantly shortened at all concentrations of Cu. Zinc caused an extension in larval development time at the highest concentration (100 mg), and caused a shortening in females and males' lifetime at all concentrations. The observed changes in biomarkers can be used as the illustration of potential toxic effects of high levels of Cu and Zn in organisms.

Histomorphology of the Malpighian Tubules and the Chemical Composition of the Spherocrystals in the Tubule Epithelial Cells of Adult Leptophyes albovittata (Kollar, 1833) (Orthoptera, Tettigoniidae)

In insects, the number, cytological and histological structures, and the spherocrystals of the Malpighian tubules (MTs) can vary considerably in different insect groups. These differences are considered important because they can be used as taxonomic characters. For this purpose, the ultrastructure of the MT epithelial cells in Leptophyes albovittata (Kollar, 1833) (Orthoptera, Tettigoniidae) was examined by light microscopy, scanning electron microscopy, and transmission electron microscopy. The wall of each tubule consists of a single layer of cells. These cells have round-shaped nuclei. Two different cell types were demonstrated in the tubule cell. These are cells that have electron-dense cytoplasm and electron-lucent cytoplasm. It was observed that the cytoplasm of these cells has many spherocrystals. The chemical composition of the spherocrystals was found to be high in carbon, phosphorus, and manganese in tubule cells.

Nickel oxide nanoparticles induce genotoxicity and cellular alterations in the ground beetle Blaps polycresta (Coleoptera: Tenebrionidae)

Nickel nanoparticles (Ni-NPs) have advantageous applications in the industry; however, little is known of their adverse effects on biological tissues. In the present study, the ground beetle Blaps polycresta was employed as a sensitive indicator for nickel oxide nanoparticles (NiO-NPs) toxicity. Adult male beetles were injected with six dose levels of NiO-NPs (0.01, 0.02, 0.03, 0.04, 0.05, and 0.06 mg/g body weight). Mortality was reported daily over 30 days under laboratory conditions to establish an LD₅₀. Nickel was detected in the testicular tissues of the beetles using X-ray analysis and transmission electronic microscopy. Beetles treated with the sublethal dose of 0.02 mg/g were selected to observe molecular, cellular, and subcellular changes. Gene transcripts of HSP70, HSP90, and MT1 were found to be increased >2.5-, 1.5-, and 2-fold, respectively, in the treated group compared with the controls. Decreased gene expression of AcPC01, AcPC02, and AcPC04 (≤1.5-, ≤2-, and < 2.5-fold, respectively, vs. controls) also were reported in the treated group. Under light microscopy, various structural changes were observed in the testicular tissues of the treated beetles. Ultrastructure observations using scanning and transmission electron microscopy showed severe damage to the subcellular organelles as well as deformities of the heads and flagella of the spermatozoa. Therefore, the present study postulated the impact of NiO-NPs in an ecological model.

Oxidative stress parameters, DNA damage and expression of HSP70 and MT in midgut of Trachyderma hispida (Forskål, 1775) (Coleoptera: Tenebrionidae) from a textile industry area

The textile mill industry is one of the major sources of pollution and contributors of metal contaminants to the environment. At the same time, the industry is important for global economy. Pollution caused by the textile industry is characteristic due to a unique set of potentially toxic substances. Darkling beetles (Coleoptera, Tenebrionidae), which live in all biogeographical regions, are especially common in soil quality and soil degradation studies. Our study was designed to assess long-term effects of textile industry (which generates specific pollution) on soil organisms, namely Trachyderma hispida. We especially wanted to find out what changes allow the species to survive and adapt to these specific conditions. Energy-dispersive X-ray spectroscopy of soil and midgut tissues of T. hispida sampled from a polluted site in the Edku textile industrial area in Egypt revealed a high accumulation of chemical elements, compared to a reference site. The concentration of elements in soil was well correlated with their concentration in the midgut of insects. Activity of superoxide dismutase, catalase, ascorbate peroxidase and glutathione S-transferase were negatively correlated with concentration of elements in soil and in the midgut. Meanwhile, malondialdehyde concentration in the midgut revealed an opposite tendency. DNA damage and expression of stress proteins, (HSP70 and metallothionein - MT) were elevated in insects from the polluted site. The activity of textile industry in the area of Edku undoubtedly causes an increase of soil pollution and, in consequence, causes a number of changes in the bodies of organisms living in these areas, including T. hispidus. Therefore, it is necessary to find a solution which limits the emission of waste from the textile industry, as well as to design modern strategies of processing, storing and utilizing it.

Facing the threat: common yellowjacket wasps as indicators of heavy metal pollution

We investigated the common wasp, Vespula vulgaris as a bioindicator and biomonitor of metals in the industrial area. Using traps, we collected 257 yellowjackets along a pollution gradient in the Harjavalta Cu-Ni smelter in Southwest Finland. Our method detected metal elements such as arsenic (As), cobalt (Co), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), zinc (Zn), and mercury (Hg) in wasps. The data analyses revealed V. vulgaris can be a proper indicator for As, Cd, Co, Cu, Ni, and Pb, rather than for Fe and Zn contamination. Body burdens of As, Cd, Co, Cu, Ni, and Pb decreased with an increase in distance from smelter. Enrichment factor (EF) followed the pattern Pb ˃ Cd ˃ As ˃ Co ˃ Cu ˃ Ni. The highest bioaccumulation (BAF) values were revealed for Cd (5.9) and the lowest for Pb (0.1). Specially designed software (WaspFacer) allowed revealing body burdens of As, Cd, Co, Cu, Ni, and Pb to be associated with rather smaller than more asymmetric facial colour markings in yellowjackets. These results add to the body of literature on how heavy metal contaminants can have tangible phenotypic effects on insects and open future opportunities for using wasps as indicators of metal pollution.

Bioaccumulation and Dispersion of Uranium by Freshwater Organisms

Uranium is the heaviest naturally occurring element on Earth. Uranium mining may result in ground and surface water contamination with potential bioaccumulation and dispersion by aquatic invertebrates with aerial stages. We investigated the effects of uranium contamination at community level in terms of abundance, richness, the composition of invertebrate communities, and functional traits. We also investigated uranium mobility across aquatic food webs and its transfer to land via the emergence of aquatic insects. We sampled water, sediment, biofilm, macrophytes, aquatic invertebrates, adult insects, and spiders in the riparian zone across sites with a gradient of uranium concentrations in stream water (from 2.1 to 4.7 µg L^-1) and sediments (from 10.4 to 41.8 µg g^-1). Macroinvertebrate assemblages differed between sites with a higher diversity and predominance of Nemouridae and Baetidae at the reference site and low diversity and predominance of Chironomidae in sites with the highest uranium concentration. Uranium concentrations in producers and consumers increased linearly with uranium concentration in stream water and sediment (p < 0.05). The highest accumulation was found in litter (83.76 ± 5.42 µg g^-1) and macrophytes (47.58 ± 6.93 µg g^-1) in the most contaminated site. Uranium was highest in scrapers (14.30 ± 0.98 µg g^-1), followed by shredders (12.96 ± 0.81 µg g^-1) and engulfer predators (7.01 ± 1.3 µg g^-1). Uranium in adults of aquatic insects in the riparian zone in all sites ranged from 0.25 to 2.90 µg g^-1, whereas in spiders it ranged from 0.96 to 1.73 µg g^-1, with no differences between sites (p > 0.05). There was a negative relationship between δ¹⁵N and uranium, suggesting there is no biomagnification along food webs. We concluded that uranium is accumulated by producers and consumers but not biomagnified nor dispersed to land with the emergence of aquatic insects.

Ultrastructure of the larval Malpighian tubules in Terrobittacus implicatus (Mecoptera: Bittacidae)

The larvae of Bittacidae, a cosmopolitan family in Mecoptera, have an interesting habit of spraying the body surface with soil through the anus after hatching, and each molts. The fine structure of Malpighian tubules, however, remains largely unknown in the larvae of Bittacidae to date. Here, we studied the ultrastructure of the larval Malpighian tubules in the hangingfly Terrobittacus implicatus (Huang & Hua) using scanning and transmission electron microscopy. The larvae of T. implicatus have six elongate Malpighian tubules at the junction of the midgut and hindgut. The tubule comprises a basal lamina, a single-layered epithelium, and a central lumen. The basal plasma membranes of the epithelial cells are conspicuously infolded and generate a labyrinth. The epithelium consists of two types of cells: large principal cells and scattered stellate cells. Mitochondria and cisterns of rough endoplasmic reticulum are numerous in the principal cells but are sparsely distributed in the stellate cells, indicating that the principal cells are active in transport. On the other hand, spherites are only abundant in the principal cells and are likely associated with the soil-spraying habit of the larvae.

Effects of Cd accumulation on cutworm Spodoptera litura larvae via Cd treated Chinese flowering cabbage Brassica campestris and artificial diets

By exposing herbivorous cutworm Spodoptera litura (Lepidoptera: Noctuidae) larvae to Cadmium (Cd) stress via Cd treated cabbages Brassica campestris and artificial diets, we investigated effects of Cd accumulation in larvae on their survival and food utilization. The results showed that Cd transferred from soils contaminated with different Cd concentrations through cabbages-larvae, and be mainly accumulated in larvae guts. There was a dose-response relationship between Cd accumulations in larvae cuticle, head, guts and Cd concentrations in artificial diets, and the highest one was found in the guts, regardless of generations. High Cd stress (10 mg kg^-1 Cd in soil, 40.6, 81.2 mg kg^-1 Cd in artificial diets) had inhibited effects on larvae growth and food utilization, whereas low Cd stress (Lvbao 701 planted in 2.5 mg kg^-1 Cd soil, 4.06 mg kg^-1 Cd in artificial diets) showed stimulated effect. Cd accumulations in the guts were significantly negative correlated with efficiency of conversion of ingested food (ECI) and relative growth rate (RGR) of larvae feeding on Cd treated diets or cabbages while were significantly positive correlated with relative consumption rate (RCR). Therefore, after S. litura larvae feed on Cd treated natural food or artificial diets, Cd could be transferred to different tissues, and mainly accumulated in the guts, which significantly affected growth and food utilization. Additionally, Cd stress via Cd treated artificial diets presented less detrimental effects on S. litura larvae than via Cd treated cabbages.

The potential role of spherocrystals in the detoxification of essential trace metals following exposure to Cu and Zn in the fighting conch Strombus (Lobatus) pugilis

Crypt cells-one of the three cell types composing Strombidae digestive tubules-are characterized by the presence of numerous metal-containing phosphate granules termed spherocrystals. We explored the bioaccumulation and detoxification of metals in Strombidae by exposing wild fighting conch Strombus pugilis for 9 days to waterborne CuSO₄ and ZnSO₄. The total amount of Cu and Zn was determined in the digestive gland and in the rest of the body by Inductively Coupled Plasma (ICP) analyses. The digestive gland spherocrystal metal content was investigated based on the semi-quantitative energy dispersive X-ray (EDX) elemental analysis. ICP analyses of unexposed individuals revealed that 87.0 ± 5.9% of the Zn is contained in the digestive gland, where its concentration is 36 times higher than in the rest of the body. Regarding Cu, 25.8 ± 16.4% of the metal was located in the digestive gland of the control individuals, increasing to 61.5 ± 16.4% in exposed individuals. Both Cu and Zn concentrations in the digestive gland increased after exposures, pointing to a potential role of this organ in the detoxification of these metals. EDX analysis of spherocrystals revealed the presence of Ca, Cl, Fe, K, Mg, P, and Zn in unexposed individuals. No difference was found in the relative proportion of Zn in spherocrystals of exposed versus control individuals. Contrastingly, copper was never detected in the spherocrystals from controls and Zn-exposed individuals, but the relative proportion of Cu in spherocrystals of Cu-exposed individuals varied from 0.3 to 5.7%. Our results show the direct role of spherocrystals in Cu detoxification.

Ultrastructural Alterations of Midgut Epithelium, But Not Greater Wing Fluctuating Asymmetry, in Paper Wasps (Polistes dominula) from Urban Environments

Polistes paper wasps can be used to monitor trace metal contaminants, but the effects of pollution on the health of these insects are still unknown. We evaluated, in a south-eastern area of Spain, whether workers of Polistes dominula collected at urban and rural sites differ in health of midgut tissue and in fluctuating asymmetry, an estimate of developmental noise. We found that wasps collected at the urban sites had abundant lead (Pb)-containing spherites, which were less visible in wasps from the rural sites. Evident ultrastructural alterations in the epithelium of the midgut of the wasps collected at the urban sites included broken and disorganized microvilli, a high amount and density of heterochromatin in the nucleus of epithelial cells, cytoplasmic vacuolization and mitochondrial disruptions. Altogether, these findings suggest a negative effect on the transmembrane transport and a less efficient transcription. On the contrary, a healthy epithelium was observed in wasps from the rural sites. These differences may be preliminarily linked with levels of lead pollution, given that wasps from urban sites had double the Pb concentrations of wasps from rural sites. Level of fluctuating asymmetry was unrelated to wasp origin, thus suggesting no link between developmental noise and Pb-driven pollution.

Ultrastructure of fat body cells and Malpighian tubule cells in overwintering Scoliopteryx libatrix (Noctuoidea)

The herald moths, Scoliopteryx libatrix, overwinter in hypogean habitats. The ultrastructure of their fat body (FB) cells and Malpighian tubule (MT) epithelial cells was studied by light microscopy and transmission electron microscopy, and essential biometric and biochemical measurements were performed. The FB was composed of adipocytes and sparse urocytes. The ultrastructure of both cells did not change considerably during this natural starvation period, except for rough endoplasmic reticulum (rER) which became more abundant in March females. In the cells, the reserve material consisted of numerous lipid droplets, glycogen rosettes, and protein granula. During overwintering, the lipid droplets diminished, and protein granula became laminated. The MTs consisted of a monolayer epithelium and individual muscle cells. The epithelial cells were attached to the basal lamina by numerous hemidesmosomes. The apical plasma membrane was differentiated into numerous microvilli, many of them containing mitochondria. Nuclei were surrounded by an abundant rER. There were numerous spherites in the perinuclear part of the cells. The basal plasma membrane formed infoldings with mitochondria in between. Nuclei were located either in the basal or in the central part of the cells. During overwintering, spherites were gradually exploited, and autophagic structures appeared: autophagosomes, autolysosomes, and residual bodies. There were no statistical differences between the sexes in any measured biometric and biochemical variables in the same time frames. The energy-supplying lipids and glycogen, and spherite stores were gradually spent during overwintering. In March, the augmented rER signified the intensification of synthetic processes prior to the epigean ecophase.

X-ray metal assessment and ovarian ultrastructure alterations of the beetle, Blaps polycresta (Coleoptera, Tenebrionidae), inhabiting polluted soil

X-ray analysis was applied to estimate the percentages of heavy metals in ovarian tissues of the tenebrionid beetle, Blaps polycresta. Calcium, phosphorus, sulfur, cadmium, copper, and zinc were the most common detected metals in ovaries of insects collected from reference and polluted sites. Only cadmium showed significantly higher percentages in the polluted ovaries compared with the reference ones. Ultrastructure investigation revealed severe alterations in polluted ovaries both in the tropharium and in the vitellarium. Contraction of nuclear membrane of trophocytes was observed; therefore, cavities and spaces appeared in the cytoplasm followed by nuclear pyknosis. In the vitellarium, fragmentation of chromatin materials in nuclei of the follicular cells was detected. The cytoplasm was poor in the rough endoplasmic reticulum and mitochondria. Damage of yolk bodies occurred in addition to break off in the layer of microvilli. Accumulation of electron-dense vesicles and multivesicular bodies were observed in both reference and polluted ovaries. These alterations in ovarian ultrastructure of B. polycresta show the severe impact of cadmium pollution on cell organelles of insects and could be used as an interesting tool for monitoring heavy metals inside the body organs due to soil pollution.

Feeding-induced phenol production in Capsicum annuum L. influences Spodoptera litura F. larval growth and physiology

We studied the role of induced plant phenols as a defense response to insect herbivory. Phenolic compounds were induced in Capsicum annuum L., the source of many culinary peppers, after feeding by different stages of the insect pest, Spodoptera litura F. The phenols were identified and quantified using high performance liquid chromatography (HPLC) and effects produced by these phenols on larval development were studied. Vanillic acid was identified in plants challenged by second, fourth, and fifth instar larvae, but not in plants challenged by third instar nor unchallenged plants. Syringic acid production was induced in chili plants infested with second (0.429 ± 0.003 μg/g fresh weight, fourth (0.396 ± 0.01 μg/g fresh weight), and fifth instar (5.5 ± 0.06 μg/g fresh weight) larvae, compared to untreated plants (0.303 ± 0.01 μg/g fresh weight) plants. Leaves surface treated with the rutin deterred oviposition. Dietary exposure to chlorogenic acid, vanillic acid, syringic acid, sinapic acid, and rutin led to enhanced activities of detoxifying enzymes, β-glucosidase, carboxyl esterase, glutathione S-transferase, and glutathione reductase in the midgut tissues of all the larval instars, indicating the toxic nature of these compounds. Protein carbonyl content and acetylcholinesterase activity was analyzed to appreciate the role of induced plant phenols in insect protein oxidation and terminating nerve impulses.

Evidence of immunocompetence reduction induced by cadmium exposure in honey bees (Apis mellifera)

In the last decades a dramatic loss of Apis mellifera hives has been reported in both Europe and USA. Research in this field is oriented towards identifying a synergy of contributing factors, i.e. pathogens, pesticides, habitat loss and pollution to the weakening of the hive. Cadmium (Cd) is a hazardous anthropogenic pollutant whose effects are proving to be increasingly lethal. Among the multiple damages related to Cd contamination, some studies report that it causes immunosuppression in various animal species. The aim of this paper is to determine whether contamination by Cd, may have a similar effect on the honey bees' immunocompetence. Our results, obtained by immune challenge experiments and confirmed by structural and ultrastructural observations show that such metal causes a reduction in immunocompetence in 3 days Cd exposed bees. As further evidence of honey bee response to Cd treatment, Energy Dispersive X-ray Spectroscopy (X-EDS) has revealed the presence of zinc (Zn) in peculiar electron-dense granules in fat body cells. Zn is a characteristic component of metallothioneins (MTs), which are usually synthesized as anti-oxidant and scavenger tools against Cd contamination. Our findings suggest that honey bee colonies may have a weakened immune system in Cd polluted areas, resulting in a decreased ability in dealing with pathogens.

Deltamethrin-Mediated Toxicity and Cytomorphological Changes in the Midgut and Nervous System of the Mayfly Callibaetis radiatus

Immature instars of mayflies are important constituents of the food web in aquatic ecosystems (especially in Neotropical regions) and they are among the most susceptible arthropods to pyrethroid insecticides. These insecticides have been recognized as important stressors of freshwater ecosystems, but their cellular effects in aquatic insects have been neglected. Here, we assessed the susceptibility to deltamethrin (a typical type II pyrethroid) as well as the deltamethrin-mediated cytomorphological changes in the central nervous system and midgut of the mayfly Callibaetis radiatus. While the deltamethrin LC50 for 24 h of exposure was of 0.60 (0.46-0.78) μg of a.i/L, the survival of C. radiatus was significantly reduced in deltamethrin concentrations ≥ 0.25 μg a.i/L at 96 h of exposure. Sub-lethal deltamethrin exposure severely affected the cytomorphology of C. radiatus midgut (e.g., muscle layer retraction, cytoplasm vacuolation, nucleus and striated border disorganization) and also induced slight cytomorphological changes in the brain (e.g., presence of pyknotic nuclei) and in the thoracic ganglia (e.g., vacuolation of neurons and presence of pyknotic nuclei) of these insects. However, DNA damage was absent in all of these organs, suggesting that the sublethal cellular stress induced by deltamethrin might disrupt physiological processes (e.g., metabolism or electrical signal transmission) rather than cause cell death (e.g., apoptosis) in C. radiatus. Thus, our findings indicated that deltamethrin actions at cellular levels represent a clear indication of sublethal effects on the C. radiatus survival abilities.

Response of the common cutworm Spodoptera litura to lead stress: changes in sex ratio, Pb accumulations, midgut cell ultrastructure

When cutworm Spodoptera litura larvae were fed on the diets with different lead (Pb) concentrations for one or five generations, changes in growth and food utilization were recorded; Pb accumulations were detected by Atomic Absorption Spectrophotometer; changes in midgut cell ultrastructure were observed by Transmission Electron Microscopy (TEM). The effects of Pb stress on S. litura growth and food utilization differed significantly between insects of the 1st and 5th generation. The male-female rate of 200mgkg(-1) Pb treatment from the 1st generation and 50mgkg(-1) Pb treatment from the 5th generation was significantly higher than control. No significant difference of Pb accumulations was found in larvae, pupae and adults between the 1st and 5th generation. No significant difference of Pb accumulations in corresponding tissues of larvae was found between male and female. Compared to fat body, hemolymph, head, foregut and hindgut, the highest Pb accumulation was found in migut of larvae exposed to 200mgkg(-1) Pb. TEM showed that expanded intercellular spaces were observed in Pb-treated midgut cells. The nuclei were strongly destroyed by Pb stress, evidenced by chromatin condensation and destroyed nuclear envelope. Mitochondria became swollen with some broken cristae after exposure to Pb. Therefore, neither gender nor progeny difference was present in Pb accumulations of S. litura, although effects of Pb stress on S. litura growth and food utilization differed from different generations and genders. Pb accumulations in midgut caused pathological changes in cells ultrastructure, possibly reflected the growth and food utilization of S. litura.

Transcriptional response of two metallothionein genes (OcMT1 and OcMT2) and histological changes in Oxya chinensis (Orthoptera: Acridoidea) exposed to three trace metals

This study evaluated the transcriptional responses of two metallothionein (MT) genes (OcMT1 and OcMT2) in various tissues (brain, optic lobe, Malpighian tubules, fat bodies, foregut, gastric caeca, midgut and hindgut) of Oxya chinensis (Thunberg) (Orthoptera: Acridoidea) after exposed to the trace metals cadmium (Cd), copper (Cu) and zinc (Zn) for 48h. The study revealed that the exposure of O. chinensis to each of the three metals at the median lethal concentration (LC50) or lower concentration(s) up-regulated the transcriptions of both OcMT1 and OCMT2 in the eight tissues except for OcMT1 and OcMT2 with Cd in brain and gastric caeca, respectively, and OcMT2 with Cu in gastric caeca. These results suggested that the exposure of O. chinensis to the metals may enhance MT biosynthesis that protects tissues by binding these metals in various tissues. To examine possible histopathological effect of the metals, we examined the histological changes in the fat bodies after O. chinensis was exposed to each of these metals at LC50. The exposure of Cd significantly reduced the size and number of adipocytes as compared with the control. However, such an effect was not observed in O. chinensis exposed to either Cu or Zn. These results suggested that fat bodies might be either significantly affected by Cd or play a crucial role in detoxification of excessive trace metals.

Honey Bees (Apis mellifera, L.) as Active Samplers of Airborne Particulate Matter

Honey bees (Apis mellifera L.) are bioindicators of environmental pollution levels. During their wide-ranging foraging activity, these hymenopterans are exposed to pollutants, thus becoming a useful tool to trace the environmental contaminants as heavy metals, pesticides, radionuclides and volatile organic compounds. In the present work we demonstrate that bees can also be used as active samplers of airborne particulate matter. Worker bees were collected from hives located in a polluted postmining area in South West Sardinia (Italy) that is also exposed to dust emissions from industrial plants. The area is included in an official list of sites of national interest for environmental remediation, and has been characterized for the effects of pollutants on the health of the resident population. The head, wings, hind legs and alimentary canal of the bees were investigated with Scanning Electron Microscopy coupled with X-ray spectroscopy (SEM-EDX). The analyses pointed to specific morphological and chemical features of the particulate, and resulted into the identification of three categories of particles: industry -, postmining -, and soil –derived. With the exception of the gut, all the analyzed body districts displayed inorganic particles, mostly concentrated in specific areas of the body (i.e. along the costal margin of the fore wings, the medial plane of the head, and the inner surface of the hind legs). The role of both past mining activities and the industrial activity close to the study area as sources of the particulate matter is also discussed. We conclude that honey bees are able to collect samples of the main airborne particles emitted from different sources, therefore could be an ideal tool for monitoring such a kind of pollutants.

The toxicity of NaF on BmN cells and a comparative proteomics approach to identify protein expression changes in cells under NaF-stress: impact of NaF on BmN cells

Fluorides negatively affect the development of organisms and are a threat to human health and environmental safety. In this study, Bombyx mori N cell line (BmN) were used to explore effects of NaF on insect cells. We found that 8h (hrs) culture with high concentration of NaF (≥ 1 mM) induced significantly morphological changes. Dose-response curves of 72 h continuously cultured BmN treated with NaF showed that the half inhibitory concentration (IC50) value was 56.60 μM. Treatment of BmN with 100 and 300 μM of NaF induced apoptosis and necrosis. 2-D electrophoresis of whole cell extracted from BmN showed that treatment with 300 μM NaF up-regulated 32 proteins and down-regulated 11 proteins when compared with controls. We identified 5 different proteins by MALDI-TOF MS, and 4 of them were identified for the first time, including 2 up-regulated proteins (mitochondrial aldehyde dehydrogenase ALDH2 and prohibitin protein WPH) and 2 down-regulated proteins (calreticulin precursor CRT and DNA supercoiling factor SCF). These observations were further confirmed by fluorescence quantitative PCR. Together, our data suggest that these target proteins could be regarded as targets influenced by NaF and also provide clues for studies on the response metabolism pathway under NaF stress.

Lepidopteran insect susceptibility to silver nanoparticles and measurement of changes in their growth, development and physiology

Increased use of nanomaterials in various fields of science has lead for the need to study the impact of nanomaterial on the environment in general and on insect and plant life in particular. We studied the impact of silver nanoparticles (AgNPs) on growth and feeding responses of two lepidopteran pests of castor plant (Ricinus communis L.) namely Asian armyworm, Spodoptera litura F. and castor semilooper, Achaea janata L. Larvae were fed with PVP coated-AgNPs treated castor leaf at different concentrations and their activity was compared to that of silver nitrate (AgNO3) treated leaf diets. Larval and pupal body weights decreased along with the decrease in the concentrations of AgNPs and AgNO3 in both the test insects. Low amounts of silver were accumulated in the larval guts, but major portion of it was eliminated through the feces. Ultrastructural studies of insect gut cell using Transmission Electron Microscopy (TEM) showed accumulation of silver nanoparticles in cell organelles. Changes in the antioxidative and detoxifying enzymes of the treated larva were estimated. The effect of treatments showed differences in the activities of detoxifying enzymes, carboxylesterases (CarE), glucosidases (Glu) and glutathione S-transferases (GST) in the larval gut. Activities of superoxide dismutase, catalase, and peroxidase were also altered in the larval bodies due to the AgNPs treatments, suggesting that exposure of larvae to nanoparticles induces oxidative stress, which is countered by antioxidant enzymes. Induction of these enzymes may be an effective detoxification mechanism by which the herbivorous insect defends itself against nanoparticle treatment.

Heavy metal bioaccumulation and mobility from rice plants to Nilaparvata lugens (Homoptera: Delphacidae) in China

Samples of soils, rice plants, and the adult, long-winged, brown planthoppers, Nilaparvata lugens (Stål) (Homoptera: Delphacidae), were collected from 18 sites of 9 regions in southern China. The concentrations of seven elements (Cu, Zn, As, Mo, Ag, Cd, and Pb) were measured using inductively coupled plasma mass spectrometry. Heavy metal mobility and bioaccumulation were analyzed in the rice plant-N. lugens system. The concentrations of Zn, As, Cd, and Pb in rice plants were positively correlated with their relevant concentrations in soil samples The bioconcentration factors of the seven elements in the rice plant-N. lugens system showed that the order of metal accumulation was Mo>Zn>Ag>Cd>Cu>Pb>As. In particular, Mo and Zn showed significantly high accumulation in N. lugens. A cluster analysis and factor analysis showed that the bioaccumulation of these seven elements in the rice plant-N. lugens system could be classified into two groups, closely related to their molar mass. The first group consisted of five elements with relatively light molar masses: Cu, Zn, As, Mo, and Ag. Cu and Zn, which have nearly equal molar masses, showed similar accumulation levels in N. lugens. The second group included two elements with relatively heavy molar masses: Cd and Pb. This study demonstrated that bioaccumulation of seven heavy metals was regular in the rice plant-N. lugens system. N. lugens could be used as bioindicators of the contaminated degree for Zn in rice paddy fields. This information may provide a basis for future ecological research on the bioaccumulation mechanism in N. lugens.

The effects of cadmium or zinc multigenerational exposure on metal tolerance of Spodoptera exigua (Lepidoptera: Noctuidae)

The effects of ten generational zinc or cadmium pre-exposure on metal tolerance among beet armyworm Spodoptera exigua individuals were compared. These effects were assessed in animals from the 11th generation, reared on a diet either uncontaminated or contaminated with metal (cadmium or zinc). The survival rate of larvae and the degree of metal accumulation (in larvae, pupae and moths; among larval organs: gut and fat body) were analysed. Catalase, superoxide dismutase and glutathione transferase activity in larval organs of individuals subjected to different metal treatments were also measured. Animals transferred from control rearing to metals (cadmium or zinc) in the 11th generation, as well as those from multigenerational zinc treatment, but not from multigenerational cadmium treatment, had a significantly lower survival rate than control animals. Insects from the groups with the high metal treatment had high bioaccumulation factors (above 3.7 and 2.3 following cadmium and zinc, respectively). Cadmium (but not zinc) pre-exposure had a significant effect on metal accumulation in larvae. Multigenerational metal pre-exposure seemed to have mainly a negative effect on glutathione transferase activity in the gut of larvae from the 11th generation, in the case of the individuals exposed to metal other than that used in pre-exposure treatment or kept in control conditions. However, in the case of zinc pre-exposure, such effect was only apparent when zinc was replaced by cadmium. The long-term effect of cadmium on catalase activity in larvae was found.

Micro x-ray absorption spectroscopic analysis of arsenic localization and biotransformation in Chironomus riparius Meigen (Diptera: Chironomidae) and Culex tarsalis Coquillett (Culicidae)

The distribution and speciation of arsenic (As) were analyzed in individuals of various life stages of a midge, Chironomus riparius, and the mosquito Culex tarsalis exposed to 1000 μg/l arsenate. X-ray absorption spectroscopy (XAS) revealed that C. riparius larvae accumulate As in their midgut, with inorganic arsenate [As(V)] being the predominant form, followed by arsenite [As(III)] and an As-thiol. Reduced concentrations of As in pupal and adult stages of C. riparius indicate excretion of As between the larval and pupal stages. In adults, As was limited to the thorax, and the predominant form was an As-thiol. In Cx. tarsalis, As was not found in high enough concentrations to determine As speciation, but the element was distributed throughout the larva. In adults, As was concentrated in the thorax and eyes of adults. These results have implications for understanding the biotransformation of As and its movement from aquatic to terrestrial environments.

Response of the common cutworm Spodoptera litura to zinc stress: Zn accumulation, metallothionein and cell ultrastructure of the midgut

By exposing the common cutworm Spodoptera litura Fabricius larvae to a range of Zinc (Zn) stress, we investigated the effects of dietary Zn on Zn accumulation, metallothionein (MT), and on the ultrastructure of the midgut. The techniques we used were inductively coupled plasma-atomic emission spectrometer (ICP-AES), real-time PCR combined with cadmium-hemoglobin total saturation, and transmission electron microscopy (TEM), respectively. There was a significant dose-response relationship between the Zn accumulations in the midgut of the larvae and the Zn concentrations in the diet. Furthermore, both MT content and MT gene expression in the midgut were significantly induced in the 50-500 mg Zn/kg treatments, and were significantly positively correlated with the Zn accumulations in the midgut. When S. litura larvae were fed with the diet treated with 500 mg Zn/kg, Zn accumulation and MT content in the midgut was 4450.85 mg Zn/kg and 372.77 mg/kg, respectively, thereafter there was a little increase; the level of MT gene expression was maximal, thereafter there was a sharp decrease. TEM showed that numerous electron-dense granules (EDGs) and vacuoles appeared in the cytoplasm of the midgut cells, their number and size being closely correlated with the Zn accumulations in the midgut. Moreover, the nuclei were strongly influenced by Zn stress, evidenced by chromatin condensation and irregular nuclear membranes. Therefore, after being exposed to Zn in the threshold (500 mg Zn/kg) range, S. litura larvae could accumulate Zn in the midgut, which led to the induction of MT and changes in cell ultrastructure (mainly the presence of EDGs). The induction of MT and precipitation of Zn in EDGs may be the effective detoxification mechanisms by which the herbivorous insect S. litura defends itself against heavy metals.

Lead exposure improves the tolerance of Spodoptera litura (Lepidoptera: Noctuidae) to cypermethrin

Many ecological factors such as heavy metals can affect the tolerance of herbivorous insects to chemical insecticide. Spodoptera litura larvae exposed to lead (Pb) (0-100 mg kg(-1) in artificial diet) did not inhibit their growth. After 96 h of Pb (0-100 mg kg(-1)) exposure, topical application and feeding of cypermethrin to S. litura decreased their mortality and increased weight gain. Moreover, the mortality of S. litura treated with 25 and 50 mg kg(-1) of Pb for five generations was significantly lower than control. In addition, Pb accumulation was detected in midgut, fat body, brain and hemolymph, and its highest level was in the midgut. Furthermore, there was a significant negative correlation between Pb accumulation in fat body and mortality after topical application of cypermethrin. After 96 h of Pb exposure, there was increase expression of detoxification enzymes (CYP9A39 and CYP6B47) in midgut and fat body of S. litura. Therefore, the tolerance of S. litura to cypermethrin is increased by Pb exposure at certain concentrations through Pb accumulation in body and the increase of CYP9A39 and CYP6B47 expression.