Nano- and micro-polystyrene plastics disturb gut microbiota and intestinal immune system in honeybee

Uncovering hidden dangers: The combined toxicity of abamectin and lambda-cyhalothrin on honey bees

Studying the toxic effects of pesticides on bees has consistently been a prominent area of interest for researchers. Nonetheless, existing research has predominantly concentrated on individual toxicity assessments, leaving a gap in our understanding of mixed toxicity. This study delves into the individual and combined toxic effects of abamectin (ABA) and lambda-cyhalothrin (LCY) on honey bees (Apis mellifera) in laboratory settings. We discovered that ABA (96 h-LC50 value of 0.079 mg/L) exhibited greater acute toxicity to honey bees compared to LCY (96 h-LC50 value of 9.177 mg/L). Moreover, the mixture of ABA and LCY presented an acute antagonistic effect on honey bees. Additionally, our results indicated that exposure to LCY, at medium concentration, led to a reduction in the abundance of gut core bacterium Snodgrassella. However, an increase in the abundance of Bifidobacterium was noted when exposed to a medium concentration of LCY and its mixture with ABA. Transcriptomic analysis revealed significant regulation of certain genes in the medium concentration of all three treatments compared to the control group, primarily enriching in metabolism and immune-related pathways. Following chronic exposure to field-relevant concentrations of ABA, LCY, and their mixture, there were significant alterations in the activities of immunity-related enzyme polyphenol oxidase (PPO) and detoxification enzymes glutathione S-transferase (GST) and carboxylesterase (CarE). Additionally, the expression of four genes (abaecin, cyp9e2, cyp302a1, and GstD1) associated with immune and detoxification metabolism was significantly altered. These findings suggest a potential health risk posed by the insecticides ABA and LCY to honey bees. Despite exhibiting acute antagonistic effect, mixed exposure still induced damage to bees at all levels. This study advances our knowledge of the potential adverse effects of individual or combined exposure to these two pesticides on non-target pollinators and offers crucial guidance for the use of insecticides in agricultural production.

A perspective on the impacts of microplastics on mosquito biology and their vectorial capacity

Microplastics (plastic particles <5 mm) permeate aquatic and terrestrial ecosystems and constitute a hazard to animal life. Although much research has been conducted on the effects of microplastics on marine and benthic organisms, less consideration has been given to insects, especially those adapted to urban environments. Here, we provide a perspective on the potential consequences of exposure to microplastics within typical larval habitat on mosquito biology. Mosquitoes represent an ideal organism in which to explore the biological effects of microplastics on terrestrial insects, not least because of their importance as an infectious disease vector. Drawing on evidence from other organisms and knowledge of the mosquito life cycle, we summarise some of the more plausible impacts of microplastics including physiological, ecotoxicological and immunological responses. We conclude that although there remains little experimental evidence demonstrating any adverse effect on mosquito biology or pathogen transmission, significant knowledge gaps remain, and there is now a need to quantify the effects that microplastic pollution could have on such an important disease vector.

Unravelling the microplastic menace: Different polymers additively increase bee vulnerability

Microplastics (MPs) are growing and ubiquitous environmental pollutants and represent one of the greatest contemporary challenges caused by human activities. Current research has predominantly examined the singular toxicological effects of individual polymers, neglecting the prevailing reality of organisms confronted with complex contaminant mixtures and potential synergistic effects. To fill this research gap, we investigated the lethal and sublethal effects of two common MPs, polystyrene (PS - 4.8-5.8 μm) and poly(methyl methacrylate) (PMMA - 1-40 μm), and their combination (MIX), on the pollinating insect Apis mellifera. For each treatment, we evaluated the oral toxicity of two ecologically relevant and one higher concentration (0.5, 5 and 50 mg/L) and analysed their effects on the immune system and worker survival. As immune activation can alter the cuticular hydrocarbon profile of honey bees, we used gas chromatography-mass spectrometry (GC-MS) to investigate whether MPs lead to changes in the chemical profile of foragers and behavioural assay to test whether such changes affect behavioural patterns of social recognition, undermining overall colony integrity. The results indicate an additive negative effect of PS and PMMA on bee survival and immune response, even at ecologically relevant concentrations. Furthermore, alterations in cuticle profiles were observed with both MPs at the highest and intermediate concentrations, with PMMA being mainly responsible. Both MPs exposure resulted in a reduction in the abundance of several cuticular compounds. Hive entry guards did not show increased inspection or aggressive behaviour towards exposed foragers, allowing them to enter the colony without being treated differently from uncontaminated foragers. These findings raise concerns not only for the health of individual bees, but also for the entire colony, which could be at risk if contaminated nestmates enter the colony undetected, allowing MPs to spread throughout the hive.

A systemic study of cyenopyrafen in strawberry cultivation system: Efficacy, residue behavior, and impact on honeybees (Apis mellifera L.)

The pesticide application method is one of the important factors affecting its effectiveness and residues, and the risk of pesticides to non-target organisms. To elucidate the effect of application methods on the efficacy and residue of cyenopyrafen, and the toxic effects on pollinators honeybees in strawberry cultivation, the efficacy and residual behavior of cyenopyrafen were investigated using foliar spray and backward leaf spray in field trials. The results showed that the initial deposition of cyenopyrafen using backward leaf spray on target leaves reached 5.06-9.81 mg/kg at the dose of 67.5-101.25 g a.i./ha, which was higher than that using foliar spray (2.62-3.71 mg/kg). The half-lives of cyenopyrafen in leaves for foliar and backward leaf spray was 2.3-3.3 and 5.3-5.9 d, respectively. The residues (10 d) of cyenopyrafen in leaves after backward leaf spray was 1.41-3.02 mg/kg, which was higher than that after foliar spraying (0.25-0.37 mg/kg). It is the main reason for the better efficacy after backward leaf spray. However, the residues (10 d) in strawberry after backward leaf spray and foliar spray was 0.04-0.10 and < 0.01 mg/kg, which were well below the established maximum residue levels of cyenopyrafen in Japan and South Korea for food safety. To further investigate the effects of cyenopyrafen residues after backward leaf spray application on pollinator honeybees, sublethal effects of cyenopyrafen on honeybees were studied. The results indicated a significant inhibition in the detoxification metabolic enzymes of honeybees under continuous exposure of cyenopyrafen (0.54 and 5.4 mg/L) over 8 d. The cyenopyrafen exposure also alters the composition of honeybee gut microbiota, such as increasing the relative abundance of Rhizobiales and decreasing the relative abundance of Acetobacterales. The comprehensive data on cyenopyrafen provide basic theoretical for environmental and ecological risk assessment, while backward leaf spray proved to be effective and safe for strawberry cultivation.

Association of specific gut microbiota with polyethylene microplastics caused gut dysbiosis and increased susceptibility to opportunistic pathogens in honeybees

The emergence of microplastics as contaminants has raised concerns regarding their potential toxicity. Recent studies on microplastic pollution caused by food packaging have drawn attention to its impact on health. However, despite being used extensively in food packaging, there is little knowledge about the toxicity of polyethylene microplastics (PE-MPs). Here, we studied the toxicity of PE-MPs on the model animal honeybees using different particle sizes (1 μm, 10 μm, 100 μm in diameter). Oral exposure to 100-μm PE-MPs resulted in elevated honeybee mortality and increased their susceptibility to pathogens. This is likely due to the mechanical disruption and gut microbial dysbiosis by PE-MPs. Snodgrassella, a core functional gut bacteria, was specifically enriched on the surface of PE-MPs, which perturbs the gut microbial communities in honeybees. Furthermore, the increased mortality in challenge trials with the opportunistic pathogen Hafnia alvei for PE-MPs pre-exposed honeybees revealed a potential health risk. These findings provide fresh insights into evaluating the potential hazards associated with PE-MPs.

Toxicological impacts of microplastics on virulence, reproduction and physiological process of entomopathogenic nematodes

Microplastics have emerged as significant and concerning pollutants within soil ecosystems. Among the soil biota, entomopathogenic nematodes (EPNs) are lethal parasites of arthropods, and are considered among the most effective biological agents against pests. Infective juveniles (IJs) of EPNs, as they navigate the soil matrix scavenging for arthropod hosts to infect, they could potentially encounter microplastics. Howver, the impact of microplastics on EPNs has not been fully elucidated yet. We addressed this gap by subjecting Steinernema feltiae EPNs to polystyrene microplastics (PS-MPs) with various sizes, concentrations, and exposure durations. After confirming PS-MP ingestion by S. feltiae using fluorescent dyes, we found that the PS-MPs reduced the survival, reproduction, and pathogenicity of the tested EPNs, with effects intensifying for smaller PS-MPs (0.1-1 μm) at higher concentrations (105 μg/L). Furthermore, exposure to PS-MPs triggered oxidative stress in S. feltiae, leading to increased reactive oxygen species levels, compromised mitochondrial membrane potential, and increased antioxidative enzyme activity. Furthermore, transcriptome analyses revealed PS-MP-induced suppression of mitochondrial function and oxidative phosphorylation pathways. In conclusion, we show that ingestion of PS-MPs by EPNs can compromise their fitness, due to multple toxicity effects. Our results bear far-reaching consequences, as the presence of microplastics in soil ecosystems could undermine the ecological role of EPNs in regulating pest populations.

Microplastics reach the brain and interfere with honey bee cognition

Scientific research on the impact of microplastics (MPs) in terrestrial systems is still emerging, but it has confirmed adverse health effects in organisms exposed to plastics. Although recent studies have shown the toxicological effects of individual MPs polymers on honey bees, the effects of different polymer combinations on cognitive and behavioural performance remain unknown. To fill this knowledge gap, we investigated the effects of oral exposure to spherical MPs on cognitive performance and brain accumulation in the honey bee Apis mellifera. We evaluated the acute toxicity, after a two-day exposure, of polystyrene (PS - 4.8-5.8 μm) and plexiglass (Poly(methyl methacrylate), or PMMA - 1-40 μm) MPs, and a combination of the two (MIX), at two environmentally relevant and one higher concentration (0.5, 5 and 50 mg L-1) and analysed their effects on sucrose responsiveness and appetitive olfactory learning and memory. We also used fluorescent thermoset amino formaldehyde MPs (1-5 μm) to explore whether microspheres of this diameter could penetrate the insect blood-brain barrier (BBB), using Two-Photon Fluorescence Microscopy (TPFM) in combination with an optimized version of the DISCO clearing technique. The results showed that PS reduced sucrose responsiveness, while PMMA had no significant effect; however, the combination had a marked negative effect on sucrose responsiveness. PMMA, PS, and MIX impaired bee learning and memory in bees, with PS showing the most severe effects. 3D brain imaging analysis using TFPM showed that 1-5 μm MPs penetrated and accumulated in the brain after only three days of oral exposure. These results raise concerns about the potential mechanical, cellular, and biochemical damage that MPs may cause to the central nervous system.

A global review on the abundance and threats of microplastics in soils to terrestrial ecosystem and human health

Soil is the source and sink of microplastics (MPs), which is more polluted than water and air. In this paper, the pollution levels of MPs in the agriculture, roadside, urban and landfill soils were reviewed, and the influence of MPs on soil ecosystem, including soil properties, microorganisms, animals and plants, was discussed. According to the results of in vivo and in vitro experiments, the possible risks of MPs to soil ecosystem and human health were predicted. Finally, in light of the current status of MPs research, several prospects are provided for future research directions to better evaluate the ecological risk and human health risk of MPs. MPs concentrations in global agricultural soils, roadside soils, urban soils and landfill soils had a great variance in different studies and locations. The participation of MPs has an impact on all aspects of terrestrial ecosystems. For soil properties, pH value, bulk density, pore space and evapotranspiration can be changed by MPs. For microorganisms, MPs can alter the diversity and abundance of microbiome, and different MPs have different effects on bacteria and fungi differently. For plants, MPs may interfere with their biochemical and physiological conditions and produce a wide range of toxic effects, such as inhibiting plant growth, delaying or reducing seed germination, reducing biological and fruit yield, and interfering with photosynthesis. For soil animals, MPs can affect their mobility, growth rate and reproductive capacity. At present epidemiological evidences regarding MPs exposure and negative human health effects are unavailable, but in vitro and in vivo data suggest that they pose various threats to human health, including respiratory system, digestive system, urinary system, endocrine system, nervous system, and circulation system. In conclusion, the existence and danger of MPs cannot be ignored and requires a global effort.

The digestive system of a cricket pulverizes polyethylene microplastics down to the nanoplastic scale

Microplastics (MPs; <5 mm) are a growing concern and a poorly understood threat to biota. We used a generalist insect (a cricket; Gryllodes sigillatus) to examine whether individuals would ingest and physically degrade MPs in their food. We fed crickets a range of concentrations (0, 2.5, 5, and 10% w/w) of fluorescent polyethylene MPs mixed into a standard diet and dissected the gut regions to isolate the MPs within. Comparing plastic content and fragment size within gut regions, we sought to identify whether and where crickets can fragment ingested MP particles. Given the digestive tract morphology of this species, we expected that the crickets would both ingest and egest the MPs. We also predicted that the MPs would be fragmented into smaller pieces during this digestive process. We found that G. sigillatus egested much smaller pieces than they ingested, and this fragmentation occurs early in the digestive process of this insect. We found this for both sexes as well as across the range of concentrations of MPs. The degree of plastic breakdown relative to plastic feeding time suggests that the ability to fragment MPs is intrinsic and not altered by how much time crickets have spent eating the plastics. The amount of plastics found in each region of the gut in relation to feeding time also suggests that this size and shape of PE microplastic does not cause any physical blockage in the gut. This lack of evidence for blockage is likely due to plastic breakdown. We found a ∼1000-fold reduction in plastic size occurs during passage through the digestive system, yielding particles very near nanoplastics (NPs; <1 μm), and likely smaller, that are then excreted back into the environment. These findings suggest that generalist insects can act as agents of plastic transformation in their environment if/when encountering MPs.

The response of heat shock proteins in honey bees to abiotic and biotic stressors

Honey bees, Apis mellifera, are the most important managed pollinators worldwide. They are highly impacted by various abiotic and biotic stressors, especially temperature extremes, which can lead to cellular damage and death. The induction of heat shock proteins (HSPs) has been recorded in honey bees as a response to various types of stressors. HSPs are classified into different gene families according to their molecular weights. HSPs play an important role in maintaining cellular protein homeostasis due to their contribution as molecular chaperones or co-chaperones. HSPs in honey bees have complex functions with induction even under normal colony conditions. Previous studies have suggested various functions of HSPs to protect cells from damage under exposure to environmental stressors, pollutants, and pathogens. Surprisingly, HSPs have also been found to play roles in larval development and age-related tasks. The expression of HSPs varies depending on tissue type, developmental stage, age, and stress period. This article reviews studies on HSPs (sHSPs, HSP40, HSP60, HSP70, and HSP90) in honey bees and highlights gaps in the available knowledge. This review is crucial for honey bee research, particularly in the face of climate change challenges.

Gut microbiota-driven regulation of queen bee ovarian metabolism

With the global prevalence of Varroa mites, more and more beekeepers resort to confining the queen bee in a queen cage to control mite infestation or to breed superior and robust queen bees. However, the impact of such practices on the queen bee remains largely unknown. Therefore, we subjected the queen bees to a 21-day egg-laying restriction treatment (from the egg stage to the emergence of adult worker bees) and analyzed the queen bees' ovarian metabolites and gut microbiota after 21 days, aiming to assess the queen bees' quality and assist beekeepers in better hive management. Our findings revealed a significant reduction in the relative expression levels of Vg and Hex110 genes in the ovaries of egg laying-restricted queen bees compared to unrestricted egg-laying queens. The diversity of gut microbiota in the queen bee exhibited a notable decrease, accompanied by corresponding changes in the core bacteria of the microbial community, the relative abundance of Lactobacillus and Bifidobacterium increased from 22.34% to 53.14% (P = 0.01) and from 0.053% to 0.580% (P = 0.04), respectively. The relative abundance of Bombella decreased from 25.85% to 1.720% (P = 0.002). Following egg-laying restriction, the activity of the queen bee's ovaries decreased, while the metabolism of glycerophospholipids remained or stored more lipid molecules, awaiting environmental changes for the queen bee to resume egg laying promptly. Furthermore, we observed that Bombella in the queen bee's gut may regulate the queen's ovarian metabolism through tryptophan metabolism. These findings provide novel insights into the interplay among queen egg laying, gut microbiota, and ovarian metabolism. IMPORTANCE With Varroa mite infestation, beekeepers often confine the queen bee in cages for control or breeding. However, the impact on the queen bee is largely unknown. We evaluated queen bee quality by restricting egg laying and analyzing ovarian metabolites and gut microbiota. In this study, we provided a comprehensive explanation of the expression of ovarian genes, the diversity of gut microbiota, and changes in ovarian metabolism in the queen bee. Through integrated analysis of the queen bee's gut microbiota and ovarian metabolism, we discovered that the gut microbiota can regulate the queen bee's ovarian metabolism. These findings provide valuable insights into the interplay among egg laying, gut microbiota, and the reproductive health of the queen bee. Understanding these relationships can contribute to the development of better strategies for Varroa mite control and queen bee breeding.

Nano- and Microplastics Migration from Plastic Food Packaging into Dairy Products: Impact on Nutrient Digestion, Absorption, and Metabolism

The ongoing use of plastic polymers to manufacture food packaging has raised concerns about the presence of nano- and microplastics (NMPs) in a variety of foods. This review provides the most recent data on NMPs' migration from plastic packaging into dairy products. Also discussed are the possible effects of NMPs on nutrient digestion, absorption, and metabolism. Different kinds of dairy products, including skimmed milk, whole liquid milk, powder milk, and infant formula milk, have been found to contain NMPs of various sizes, shapes, and concentrations. NMPs may interact with proteins, carbohydrates, and fats and have a detrimental impact on how well these nutrients are digested and absorbed by the body. The presence of NMPs in the gastrointestinal tract may impact how lipids, proteins, glucose, iron, and energy are metabolized, increasing the risk of developing various health conditions. In addition to NMPs, plastic oligomers released from food packaging material have been found to migrate to various foods and food simulants, though information regarding their effect on human health is limited. Viewpoints on potential directions for future studies on NMPs and their impact on nutrient digestion, absorption, and health are also presented in this review.

Microplastics and Nanoplastics Effects on Plant-Pollinator Interaction and Pollination Biology

Microplastics and nanoplastics (MNPs) contamination is an emerging environmental and public health concern, and these particles have been reported both in aquatic and terrestrial ecosystems. Recent studies have expanded our understanding of the adverse effects of MNPs pollution on human, terrestrial, and aquatic animals, insects, and plants. In this perspective, we describe the adverse effects of MNPs particles on pollinator and plant health and discuss the mechanisms by which MNPs disrupt the pollination process. We discuss the evidence and integrate transcriptome studies to investigate the negative effects of MNPs on the molecular biology of pollination, which may cause delay or inhibit the pollination services. We conclude by addressing challenges to plant-pollinator health from MNPs pollution and argue that such harmful effects disrupt the communication between plant and pollinator for a successful pollination process.

Chronic Exposure to Polystyrene Microplastic Fragments Has No Effect on Honey Bee Survival, but Reduces Feeding Rate and Body Weight

Microplastics (MPs), in the form of fragments and fibers, were recently found in honey samples collected in Ecuador as well as in honey bees collected from Denmark and China. However, little is known about how MPs impact bee health. To fill this knowledge gap, we investigated the potential toxicity of irregularly shaped polystyrene (PS)-MP fragments on honey bee health. In the first experiment of its kind with honey bees, we chronically exposed bees with a well-established gut microbiome to small (27 ± 17 µm) or large (93 ± 25 µm) PS-MP fragments at varying concentrations (1, 10, 100 µg mL^-1) for 14 days. Bee mortality, food consumption, and body weight were all studied. We found that chronic exposure to PS-MP fragments has no effect on honey bee survival, but reduced the feeding rate and body weight, particularly at 10 µg PS-MP fragments per mL, which may have long-term consequences for honey bee health. The findings of this study could assist in the risk assessment of MPs on pollinator health.

Current Knowledge on Bee Innate Immunity Based on Genomics and Transcriptomics

As important pollinators, bees play a critical role in maintaining the balance of the ecosystem and improving the yield and quality of crops. However, in recent years, the bee population has significantly declined due to various pathogens and environmental stressors including viruses, bacteria, parasites, and increased pesticide application. The above threats trigger or suppress the innate immunity of bees, their only immune defense system, which is essential to maintaining individual health and that of the colony. In addition, bees can be divided into solitary and eusocial bees based on their life traits, and eusocial bees possess special social immunities, such as grooming behavior, which cooperate with innate immunity to maintain the health of the colony. The omics approach gives us an opportunity to recognize the distinctive innate immunity of bees. In this regard, we summarize innate bee immunity from a genomic and transcriptomic perspective. The genetic characteristics of innate immunity were revealed by the multiple genomes of bees with different kinds of sociality, including honeybees, bumblebees, wasps, leaf-cutter bees, and so on. Further substantial transcriptomic data of different tissues from diverse bees directly present the activation or suppression of immune genes under the infestation of pathogens or toxicity of pesticides.

Analytical Solutions of Microplastic Particles Dispersion Using a Lotka–Volterra Predator–Prey Model with Time-Varying Intraspecies Coefficients

Discarded plastic is subjected to weather effects from different ecosystems and becomes microplastic particles. Due to their small size, they have spread across the planet. Their presence in living organisms can have several harmful consequences, such as altering the interaction between prey and predator. Huang et al. successfully modeled this system presenting numerical results of ecological relevance. Here, we have rewritten their equations and solved a set of them analytically, confirming that microplastic particles accumulate faster in predators than in prey and calculating the time values from which it happens. Using these analytical solutions, we have retrieved the Lotka–Volterra predator–prey model with time-varying intraspecific coefficients, allowing us to interpret ecological quantities referring to microplastics dispersion. After validating our equations, we solved analytically particular situations of ecological interest, characterized by extreme effects on predatory performance, and proposed a second-order differential equation as a possible next step to address this model. Our results open space for further refinement in the study of predator–prey models under the effects of microplastic particles, either exploring the second-order equation that we propose or modify the Huang et al. model to reduce the number of parameters, embedding in the time-varying intraspecies coefficients all the adverse effects caused by microplastic particles.