Effects of spinetoram and glyphosate on physiological biomarkers and gut microbes in Bombus terrestris

Combined effects of spinetoram and Microcystis aeruginosa on Daphnia pulex offspring: Maternal effects and multigenerational implications

The increasing occurrence of harmful algal blooms (HABs) in freshwater ecosystems detrimentally affect global water environments. Zooplankton's role in controlling HABs is hindered by contaminant exposure, necessitating research into combined stressors' ecological impacts. The response of Daphnia, a freshwater keystone species, to environmental stressors can be influenced by its maternal effects. Here, we investigated the combined effects of the world-widely used insecticide spinetoram and non-toxic HABs species Microcystis aeruginosa on the life-history traits of D. pulex offspring produced from different maternal food conditions. Four maternal groups were established, with each group receiving a specific blend of C. vulgaris (Ch) and M. aeruginosa (Ma) in varying proportions: A (100% Ch), B (90% Ch + 10% Ma), C (80% Ch + 20% Ma), and D (70% Ch + 30% Ma). The offspring from the third brood were gathered, and a 21-day experiment was carried out, involving various feeding groups (AA, AD, BA, BB, CA, CC, DA, and DD). Results demonstrated that grazing on M. aeruginosa by D. pulex induced maternal effects on their offspring, with the continuous exposure group showing an enhanced tolerance to M. aeruginosa. This study also unveiled that spinetoram could interfere with the molting of D. pulex, leading to developmental retardation. The Recovery Group exhibited an intriguing phenomenon: under the influence of both concentrations of the pesticide spinetoram (0.18, 0.35 μg L-1), D. pulex produced more offspring. This might be due to a combined strategy of allocating more energy towards reproduction in response to low-quality food and a potential hormetic effect from low concentrations of spinetoram. Assessing the interplay of combined stressors across multiple generations, encompassing harmful algal blooms (HABs) and environmental pollutants, is essential for predicting population responses to evolving environmental conditions. This understanding is vital for the protection and management of aquatic environments and ecosystems.

Cladosporium-Insect Relationships

The range of interactions between Cladosporium, a ubiquitous fungal genus, and insects, a class including about 60% of the animal species, is extremely diverse. The broad case history of antagonism and mutualism connecting Cladosporium and insects is reviewed in this paper based on the examination of the available literature. Certain strains establish direct interactions with pests or beneficial insects or indirectly influence them through their endophytic development in plants. Entomopathogenicity is often connected to the production of toxic secondary metabolites, although there is a case where these compounds have been reported to favor pollinator attraction, suggesting an important role in angiosperm reproduction. Other relationships include mycophagy, which, on the other hand, may reflect an ecological advantage for these extremely adaptable fungi using insects as carriers for spreading in the environment. Several Cladosporium species colonize insect structures, such as galleries of ambrosia beetles, leaf rolls of attelabid weevils and galls formed by cecidomyid midges, playing a still uncertain symbiotic role. Finally, the occurrence of Cladosporium in the gut of several insect species has intriguing implications for pest management, also considering that some strains have proven to be able to degrade insecticides. These interactions especially deserve further investigation to understand the impact of these fungi on pest control measures and strategies to preserve beneficial insects.

Insect α-Amylases and Their Application in Pest Management

Amylase is an indispensable hydrolase in insect growth and development. Its varied enzymatic parameters cause insects to have strong stress resistance. Amylase gene replication is a very common phenomenon in insects, and different copies of amylase genes enable changes in its location and function. In addition, the classification, structure, and interaction between insect amylase inhibitors and amylases have also invoked the attention of researchers. Some plant-derived amylase inhibitors have inhibitory activities against insect amylases and even mammalian amylases. In recent years, an increasing number of studies have clarified the effects of pesticides on the amylase activity of target and non-target pests, which provides a theoretical basis for exploring safe and efficient pesticides, while the exact lethal mechanisms and safety in field applications remain unclear. Here, we summarize the most recent advances in insect amylase studies, including its sequence and characteristics and the regulation of amylase inhibitors (α-AIs). Importantly, the application of amylases as the nanocide trigger, RNAi, or other kinds of pesticide targets will be discussed. A comprehensive foundation will be provided for applying insect amylases to the development of new-generation insect management tools and improving the specificity, stability, and safety of pesticides.

Gut microbiome helps honeybee (Apis mellifera) resist the stress of toxic nectar plant (Bidens pilosa) exposure: Evidence for survival and immunity

Honeybee (Apis mellifera) ingestion of toxic nectar plants can threaten their health and survival. However, little is known about how to help honeybees mitigate the effects of toxic nectar plant poisoning. We exposed honeybees to different concentrations of Bidens pilosa flower extracts and found that B. pilosa exposure significantly reduced honeybee survival in a dose-dependent manner. By measuring changes in detoxification and antioxidant enzymes and the gut microbiome, we found that superoxide dismutase, glutathione-S-transferase and carboxylesterase activities were significantly activated with increasing concentrations of B. pilosa and that different concentrations of B. pilosa exposure changed the structure of the honeybee gut microbiome, causing a significant reduction in the abundance of Bartonella (p < 0.001) and an increase in Lactobacillus. Importantly, by using Germ-Free bees, we found that colonization by the gut microbes Bartonella apis and Apilactobacillus kunkeei (original classification as Lactobacillus kunkeei) significantly increased the resistance of honeybees to B. pilosa and significantly upregulated bee-associated immune genes. These results suggest that honeybee detoxification systems possess a level of resistance to the toxic nectar plant B. pilosa and that the gut microbes B. apis and A. kunkeei may augment resistance to B. pilosa stress by improving host immunity.

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.

Bees just wanna have fungi: a review of bee associations with nonpathogenic fungi

Bee-fungus associations are common, and while most studies focus on entomopathogens, emerging evidence suggests that bees associate with a variety of symbiotic fungi that can influence bee behavior and health. Here, we review nonpathogenic fungal taxa associated with different bee species and bee-related habitats. We synthesize results of studies examining fungal effects on bee behavior, development, survival, and fitness. We find that fungal communities differ across habitats, with some groups restricted mostly to flowers (Metschnikowia), while others are present almost exclusively in stored provisions (Zygosaccharomyces). Starmerella yeasts are found in multiple habitats in association with many bee species. Bee species differ widely in the abundance and identity of fungi hosted. Functional studies suggest that yeasts affect bee foraging, development, and pathogen interactions, though few bee and fungal taxa have been examined in this context. Rarely, fungi are obligately beneficial symbionts of bees, whereas most are facultative bee associates with unknown or ecologically contextual effects. Fungicides can reduce fungal abundance and alter fungal communities associated with bees, potentially disrupting bee-fungi associations. We recommend that future study focus on fungi associated with non-honeybee species and examine multiple bee life stages to document fungal composition, abundance, and mechanistic effects on bees.

No impacts of glyphosate or Crithidia bombi, or their combination, on the bumblebee microbiome

Pesticides are recognised as a key threat to pollinators, impacting their health in many ways. One route through which pesticides can affect pollinators like bumblebees is through the gut microbiome, with knock-on effects on their immune system and parasite resistance. We tested the impacts of a high acute oral dose of glyphosate on the gut microbiome of the buff tailed bumblebee (Bombus terrestris), and glyphosate's interaction with the gut parasite (Crithidia bombi). We used a fully crossed design measuring bee mortality, parasite intensity and the bacterial composition in the gut microbiome estimated from the relative abundance of 16S rRNA amplicons. We found no impact of either glyphosate, C. bombi, or their combination on any metric, including bacterial composition. This result differs from studies on honeybees, which have consistently found an impact of glyphosate on gut bacterial composition. This is potentially explained by the use of an acute exposure, rather than a chronic exposure, and the difference in test species. Since A. mellifera is used as a model species to represent pollinators more broadly in risk assessment, our results highlight that caution is needed in extrapolating gut microbiome results from A. mellifera to other bee species.