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

Insights into Ag-NPs-mediated pathophysiology and ultrastructural aberrations in ovarian tissues of darkling beetles

With the evolution of nanostructure materials, silver nanoparticles (Ag-NPs) emerged as the predominantly exploited nanomaterial in multifarious sectors due to their versatile properties. Along with the heightening applications of Ag-NPs, however, there is increasing concern over their indubitable toxicity towards the ecosystem, which indeed affects surrounding organisms and human health. In this study, we evaluated the detrimental effects of Ag-NPs in relation to Egyptian wild female beetles, Blaps polychresta, after injection with a single dose of Ag-NPs at different doses and monitoring for 30 days to determine the sublethal dose. Accordingly, the sublethal dose revealed the lowest negative influence was found at 0.03 mg/g body weight. The adverse impacts of Ag-NPs on the ovaries of female beetles were investigated by estimating the enzyme activities, DNA damage using a comet assay, and apoptosis by means of flow cytometry. Besides, the ultrastructural abnormalities were surveyed adopting transmission electron microscopy (TEM). The results manifested comet cells of 7.67 ± 0.88% and 22.33 ± 0.51 for Ag-NPs treated and control groups, respectively. Similarly, the data from flow cytometry demonstrated a substantial reduction in viable cells associated with a significant rise in apoptotic cells for the Ag-NPs treated group in comparison with the control group. Moreover, significant disturbances in enzyme activities for the treated group were perceived correlated with evident diminutions in antioxidant enzymes. Remarkably, the ultrastructural investigation emphasized these findings, exposing considerable deformities of the ovaries in the Ag-NPs treated group compared with the control group. To the best of our knowledge, this is the first report discussing the influence of Ag-NPs at the lowest dose on ovaries of B. polychresta. Collectively, our findings would significantly contribute to considering the critical effects of Ag-NPs at low levels, in addition to the potential use of B. polychresta as a good bio-indicator in ecotoxicological analyses.

Time-delayed effects of a single application of AgNPs on structure of testes and functions in Blaps polychresta Forskal, 1775 (Coleoptera: Tenebrionidae)

Silver nanoparticles (AgNPs) are currently the most frequently used engineered nanoparticles. The penetration of AgNPs into ecosystems is undeniable, and their adverse effects on organism reproduction are of fundamental importance for ecosystem stability. In this study, the survival time of the Egyptian beetle Blaps polychresta Forskal, 1775 (Coleoptera: Tenebrionidae), after a single application of 7 different doses, was calculated for 30 days. Then, for the group for which the effect on mortality was calculated as LOAEL - the Lowest Observed Adverse Effect Level, namely, 0.03 mg AgNPs/g body weight (b.w.t.), the following were assessed: structure and ultrastructure of gonads by TEM and SEM, cell viability by cytometry, DNA damage by the comet assay, and a variety of stress markers by spectrophotometric methods. A dose-dependent reduction in the survival time of the insects was revealed. Detailed analysis of the testes of beetles treated with 0.03 mg AgNPs/g b.w.t. revealed numerous adverse effects of nanoparticles in structure and ultrastructure, accompanied by increased apoptosis (but not necrosis), increased DNA damage, increased lipid peroxidation, and decreased levels of antioxidant enzymes. Most likely, the observed results are connected with the gradual release of Ag⁺ from the surface of the nanoparticles, which, once applied, are internalized in cells and become a long-lasting, stable source of Ag⁺ ions. Thus, a single exposure to AgNPs may have the effects of chronic exposure and lead to structural damage and dysfunction of the gonads of B. polychresta.

DNA damage and ovarian ultrastructural lesions induced by nickel oxide nano-particles in Blaps polycresta (Coleoptera: Tenebrionidae)

Nickel oxide nanoparticles (NiO-NPs) have extensively used in industrial and consumer products. The present study conducted to gain more knowledge about the safe use of NiO-NPs and also to understand their impact on the environment and biological systems. Herein, we examined the genotoxic and ultra-structural effects of a sublethal dose of NiO-NPs (0.03 mg/g) on the ovarian tissues of the ground beetle, Blaps polycresta. The mean diameter of NiO-NPs was 24.49 ± 3.88 nm, as obtained through transmission electron microscopy (TEM). In terms of DNA damage levels, the frequency of micronucleus (MN) formation was highly significant in the NiO-NPs treated group versus the controls. Besides, NiO-NPs treatment resulted in a significant increase in the tail length of comets. Further, electron microscopy revealed a progressive increase in chromatin condensation of the ovarian nurse and follicular cells, in addition to the accumulation of lysosomes and endo-lysosomes in their cytoplasm. In conclusion, NiO-NPs are capable of gaining access to the ovary of B. polycresta and causing DNA damage and a high degree of cellular toxicity in the ovarian cells. The present study highlights, for the first time, the adverse effects of these NPs to female gonads of insects and raised the concern of its genotoxic potential. It would be of interest to investigate NiO-NPs mediated intracellular ROS generation in future studies.

DNA damage and oogenesis anomalies in Pimelia latreillei (Coleoptera: Tenebrionidae) induced by heavy metals soil pollution

The present study used Pimelia latreillei as a biomonitoring insect for heavy metals soil pollution in a populated industrial area at Zawya Abd El-Qader, Alexandria, Egypt. Comet assay and histological analysis were applied to evaluate the potential risk of heavy metals. X-ray analysis of the soil samples collected from the polluted site revealed significantly increased metal percentages compared with the reference site. Moreover, a significant increase in metal percentages was detected by the X-ray analysis in insect ovaries collected from the polluted site. The Tail DNA length was significantly greater in the insects collected from the polluted site-47.6% compared with 11.4% at the reference site. Pronounced disruptions in oogenesis were observed through histological and ultrastructure investigations in insects collected from the polluted site. The study summarized the potential utility of insect biomonitors in predicting the effect of heavy metals soil pollution on occupational health.

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

The risk element accumulation ability of two groups of epigeic species, insects from families Coleoptera and Hymenoptera (namely Formicidae), was determined and related to soil risk element content and bioaccessibility. The study was conducted in the district of Příbram, Czech Republic, which was characterised by extremely high aged pollution in the soils, including risk elements, especially As, Pb, Zn and Cd, due to the former mining and smelting activity. Four sampling sites differing in their pseudo-total risk element contents were selected and composite samples of individuals representing either Coleoptera or Formicidae were sampled at the individual sampling points. The results indicate the ability of Coleoptera and Formicidae organisms to accumulate risk elements, especially at the location with extremely high soil risk element content. In soil containing up to 841 mg As kg^-1, 84.6 mg Cd kg^-1, 4250 mg Pb kg^-1 and 8542 mg Zn kg^-1, contents in insect bodies reached 239 mg As kg^-1 As, 24.2 mg Cd kg^-1, 70.4 mg Pb kg^-1 and 335 mg Zn kg^-1 in beetles and up to 20.9 mg As kg^-1, 29.9 mg Cd kg^-1, 111 mg Pb kg^-1 and 657 mg Zn kg^-1 in ants. Therefore, bioaccumulation factors (BAFs) varied between 0.02 and 0.55. Increasing Cd content in Coleoptera bodies with increasing soil pseudo-total element content was observed only among the investigated elements. However, the results indicate increasing BAF values with decreasing soil element levels, especially for Cd, Pb and Zn, indicating limited uptake of elements by the organisms living in contact with extremely contaminated soil.

Isoenzymes and protein polymorphism in Blaps polycresta and Trachyderma hispida (Forsskål, 1775) (Coleoptera: Tenebrionidae) as biomarkers for ceramic industrial pollution

The expression levels of Esterase Isoenzyme and total soluble protein fractionation were studied in two coleopteran insects Blaps polycresta and Trachyderma hispida to evaluate the possible hazards from ceramic and plastic factories in the Khorshed Region, East of Alexandria, Egypt. Two insect collection sites were selected. The first site was the garden of the Faculty of Science, Moharram Bek, Alexandria University, which is considered a non-polluted site, and Khorshed district, considered as the polluted site. Percentages of heavy metals were estimated using SEM-X-ray microanalysis of soft tissues of both sexes of the two coleopteran insects. Esterase Isoenzymes were found to be overexpressed in B. Polycresta but not T. hispida. Female B. polycresta from the polluted site exhibited overexpression of the second and third loci. Furthermore, the females were found to be more affected than males, which only showed the overexpression of the second loci. T. hispida (females and males) collected from the reference site were found to have increased esterase activity compared with those sampled from the polluted site. The Snake-Skin™ Dialysis tubing technique, used for optimizing the protein extraction method, reflected the highest quantified proteins compared to other, traditional methods. SDS polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the whole-body protein reflected definite variations between T. hispida and B. polycresta in fraction number and activity at the two sites. Varied expression levels for metallothionein (MT) heavy metal resistance proteins for B. polycresta and T. hispida were also detected in the study. Based on these results, we suggest that biochemical biomarkers could infer environmental hazards, B. polycresta and T. hispida are successful biomarkers for heavy metal pollution.

Beetles as Model Organisms in Physiological, Biomedical and Environmental Studies - A Review

Model organisms are often used in biological, medical and environmental research. Among insects, Drosophila melanogaster, Galleria mellonella, Apis mellifera, Bombyx mori, Periplaneta americana, and Locusta migratoria are often used. However, new model organisms still appear. In recent years, an increasing number of insect species has been suggested as model organisms in life sciences research due to their worldwide distribution and environmental significance, the possibility of extrapolating research studies to vertebrates and the relatively low cost of rearing. Beetles are the largest insect order, with their representative - Tribolium castaneum - being the first species with a completely sequenced genome, and seem to be emerging as new potential candidates for model organisms in various studies. Apart from T. castaneum, additional species representing various Coleoptera families, such as Nicrophorus vespilloides, Leptinotarsa decemlineata, Coccinella septempunctata, Poecilus cupreus, Tenebrio molitor and many others, have been used. They are increasingly often included in two major research aspects: biomedical and environmental studies. Biomedical studies focus mainly on unraveling mechanisms of basic life processes, such as feeding, neurotransmission or activity of the immune system, as well as on elucidating the mechanism of different diseases (neurodegenerative, cardiovascular, metabolic, or immunological) using beetles as models. Furthermore, pharmacological bioassays for testing novel biologically active substances in beetles have also been developed. It should be emphasized that beetles are a source of compounds with potential antimicrobial and anticancer activity. Environmental-based studies focus mainly on the development and testing of new potential pesticides of both chemical and natural origin. Additionally, beetles are used as food or for their valuable supplements. Different beetle families are also used as bioindicators. Another important research area using beetles as models is behavioral ecology studies, for instance, parental care. In this paper, we review the current knowledge regarding beetles as model organisms and their practical application in various fields of life science.

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.

Ultrastructural alterations in sperm formation of the beetle, Blaps polycresta (Coleoptera: Tenebrionidae) as a biomonitor of heavy metal soil pollution

Little is known about ultrastructural alterations induced by heavy metals pollution in insects. Therefore, the main objective of the present study is to elucidate ultrastructural changes in sperm formation of the tenebrionid beetle, Blaps polycresta as a biomonitor of heavy metal soil pollution. Metal percentages in testicular tissues of adult insects collected from reference and polluted sites were estimated using energy-dispersive X-ray microanalysis (EDX). Only cadmium, among eight detected metals, showed significantly higher percentages in the polluted testes compared with the reference ones. Ultrastructure investigation revealed severe alterations both in spermatogenic and spermiogenic stages of the polluted insects. Some cells were totally eroded. No spermatozoa were observed in all the examined cysts. Most degenerations were confined to the flagella of spermatids having enlarged vacuolated cytoplasm and malformed mitochondrial derivatives. Groups of multiple axial filaments were appeared in the form of bi-and tetra-flagellate spermatids. Electron dense vesicles were observed in almost all stages of the polluted testes. It is a novel trend in which ultrastructural alterations in sperm formation of insects could be used as a promising biomonitoring and risk assessment tool for heavy metal soil pollution.