The countryside or the city: Which environment is better for the honeybee?

Foraging Activity of Honey Bees (Apis mellifera L., 1758) and Exposure to Cadmium: a Review

Honey bees are commonly exposed to a broad spectrum of xenobiotics, including heavy metals. Heavy metal toxicity is of concern in the context of global pollinator declines, especially since honey bees seem to be particularly susceptible to xenobiotics in general. Here we summarize current knowledge on the interplay between cadmium, one of the most toxic and mobile elements in the environment, and honey bees, the primary managed pollinator species worldwide. Overall, cadmium pollution has been shown to be ubiquitous, affecting industrial, urban and rural areas alike. Uptake of this heavy metal by plants serves as the primary route of exposure for bees (through pollen and nectar). Reported cadmium toxicity consists of lethal and sublethal effects (reduced development and growth) in both adult and larval stages, as well as various molecular responses related to detoxification and cellular antioxidant defence systems. Other effects of cadmium in honey bees include the disruption of synaptic signalling, calcium metabolism and muscle function.

Imidacloprid disrupts larval molting regulation and nutrient energy metabolism, causing developmental delay in honey bee Apis mellifera

Imidacloprid is a global health threat that severely poisons the economically and ecologically important honeybee pollinator, Apis mellifera. However, its effects on developing bee larvae remain largely unexplored. Our pilot study showed that imidacloprid causes developmental delay in bee larvae, but the underlying toxicological mechanisms remain incompletely understood. In this study, we exposed bee larvae to imidacloprid at environmentally relevant concentrations of 0.7, 1.2, 3.1, and 377 ppb. There was a marked dose-dependent delay in larval development, characterized by reductions in body mass, width, and growth index. However, imidacloprid did not affect on larval survival and food consumption. The primary toxicological effects induced by elevated concentrations of imidacloprid (377 ppb) included inhibition of neural transmission gene expression, induction of oxidative stress, gut structural damage, and apoptosis, inhibition of developmental regulatory hormones and genes, suppression of gene expression levels involved in proteolysis, amino acid transport, protein synthesis, carbohydrate catabolism, oxidative phosphorylation, and glycolysis energy production. In addition, we found that the larvae may use antioxidant defenses and P450 detoxification mechanisms to mitigate the effects of imidacloprid. Ultimately, this study provides the first evidence that environmentally exposed imidacloprid can affect the growth and development of bee larvae by disrupting molting regulation and limiting the metabolism and utilization of dietary nutrients and energy. These findings have broader implications for studies assessing pesticide hazards in other juvenile animals.

Integrative population genetics and metagenomics reveals urbanization increases pathogen loads and decreases connectivity in a wild bee

As urbanization continues to increase, it is expected that two-thirds of the human population will reside in cities by 2050. Urbanization fragments and degrades natural landscapes, threatening wildlife including economically important species such as bees. In this study, we employ whole genome sequencing to characterize the population genetics, metagenome and microbiome, and environmental stressors of a common wild bee, Ceratina calcarata. Population genomic analyses revealed the presence of low genetic diversity and elevated levels of inbreeding. Through analyses of isolation by distance, resistance, and environment across urban landscapes, we found that green spaces including shrubs and scrub were the most optimal pathways for bee dispersal, and conservation efforts should focus on preserving these land traits to maintain high connectivity across sites for wild bees. Metagenomic analyses revealed landscape sites exhibiting urban heat island effects, such as high temperatures and development but low precipitation and green space, had the highest taxa alpha diversity across all domains even when isolating for potential pathogens. Notably, the integration of population and metagenomic data showed that reduced connectivity in urban areas is not only correlated with lower relatedness among individuals but is also associated with increased pathogen diversity, exposing vulnerable urban bees to more pathogens. Overall, our combined population and metagenomic approach found significant environmental variation in bee microbiomes and nutritional resources even in the absence of genetic differentiation, as well as enabled the potential early detection of stressors to bee health.

Insights into degradation of pharmaceutical pollutant atenolol via electrochemical advanced oxidation processes with modified Ti4O7 electrode: Efficiency, stability and mechanism

A novel active Ce-doped Ti₄O₇ (Ti/Ti₄O₇-Ce) electrode was prepared and evaluated for improvement of the refractory pollutants degradation efficiency in Electrochemical advanced oxidation processes (EAOPs). The results showed that the addition of Ce in Ti/Ti₄O₇ electrode leading to great impact on •OH generation rate and electrode stability compared to pristine Ti/Ti₄O₇ electrode. Ti/Ti₄O₇-Ce electrode presented efficient oxidation capacity for pharmaceutical pollutant atenolol (ATL) in EAOPs, which could be attributed to the improvement of indirect oxidation mediated by electro-generated •OH, as the amount of •OH production was 16.5% higher than that in Ti/Ti₄O₇ within 120 min. The operational conditions greatly influenced the ATL degradation. The degradation efficiency of ATL increased as the current density, the degradation efficiency reached 100% under pH 4, but it just removed 81% of ATL under pH 10 after 120 min treatment. Results also suggested that the inhibiting effect from the ATL degradation was mostly associated with the decreased oxidation capacity induced by water hardness and natural organic matter (NOM). It displayed a satisfactory durability after 40 cycles of experimental detections in this research. The results of study suggested that Ti/Ti₄O₇-Ce was a promising electrode for the efficient degradation of PPCPs-polluted wastewater and provided constructive suggestion for the refractory pollutants of EAOPs.

Pesticide contamination in an intensive insect predator of honey bees

Pesticides used for plant protection can indirectly affect target and non-target organisms and are identified as a major cause of insect decline. Depending on species interactions, pesticides can be transferred into the environment from plants to preys and predators. While the transfer of pesticides is often studied through vertebrate and aquatic exposure, arthropod predators of insects may represent valuable bioindicators of environmental exposure to pesticides. A modified QuEChERS extraction coupled with HPLC-MS/MS analysis was used to address the question of the exposure to pesticides of the invasive hornet Vespa velutina, a specialist predator of honey bees. This analytical method allows the accurate quantification of nanogram/gram levels of 42 contaminants in a sample weight that can be obtained from single individuals. Pesticide residues were analyzed in female workers from 24 different hornet nests and 13 different pesticides and 1 synergist, piperonyl butoxide, were identified and quantified. In 75 % of the explored nests, we found at least one compound and in 53 % of the positive samples we could quantify residues ranging from 0.5 to 19.5 ng.g^-1. In this study, hornets from nests located in sub-urban environments were the most contaminated. Pesticide residue analysis in small and easy to collect predatory insects opens new perspectives for the study of environmental contamination and the transfer of pesticides in terrestrial trophic chains.

The Honey Bee Apis mellifera: An Insect at the Interface between Human and Ecosystem Health

Simple Summary

Apis mellifera Linnaeus (1758), a honey bee, is a eusocial insect widely known for its role in pollination, an essential ecosystem service for plant biodiversity, and quality of vegetables and fruit products. In addition, honey bees and bee products are valuable bioindicators of pollutants, such as airborne particulate matter, heavy metals, and pesticides. In this review, we explore the provisioning, regulating, and cultural services provided by the honey bee, an insect at the interface between human and ecosystem health.

Abstract

The concept of ecosystem services is widely understood as the services and benefits thatecosystems provide to humans, and they have been categorised into provisioning, regulating, supporting, and cultural services. This article aims to provide an updated overview of the benefits that the honey bee Apis mellifera provides to humans as well as ecosystems. We revised the role of honey bees as pollinators in natural ecosystems to preserve and restore the local biodiversity of wild plants; in agro-ecosystems, this species is widely used to enhance crop yield and quality, meeting the increasing food demand. Beekeeping activity provides humans not only with high-quality food but also with substances used as raw materials and in pharmaceuticals, and in polluted areas, bees convey valuable information on the environmental presence of pollutants and their impact on human and ecosystem health. Finally, the role of the honey bee in symbolic tradition, mysticism, and the cultural values of the bee habitats are also presented. Overall, we suggest that the symbolic value of the honey bee is the most important role played by this insect species, as it may help revitalise and strengthen the intimate and reciprocal relationship between humans and the natural world, avoiding the inaccuracy of considering the ecosystems as mere providers of services to humans.