Vetnews | Mei 2025 14 « BACK TO CONTENTS The authors also emphasize that this accumulation can significantly affect the rectum’s microbiota, in addition to interfering with the use of the nutrients present in the pollen, since this accumulation hinders contact with the enzyme that facilitates the obtaining of nutrients. There was also a reduction in the abundance of intestinal Lactobacillus and Bifidobacterium and greater stimulation of inhibitory genes and genes related to detoxification and energy balance. Furthermore, individuals became more susceptible to the pathogen Hafnia alvei, which increased the mortality rate by up to five times (Wang et al. 2022). Deng et al. (2021) were the first to report that PS ingestion by honeybees promotes susceptibility to viral infections. During the experiments, the researchers collected samples of A. mellifera and A. cerana from six provinces in China in order to examine the presence of PMs in these environments, as well as to identify which types were most frequent; later, some bees were exposed to different concentrations (0.1, 1, 10, and 100 mg/L) of spherical PS particles with different sizes (0.5, 5, and 50 µm) in 1 mL of 50% sucrose solution for 21 days. Survival rates in the first 14 days of exposure were significantly different between groups for both species. After qPCR analysis, a reduction in the expression of CYP9Q1 and GSTD1 was noted, while catalase was upregulated. Finally, the researchers evaluated how the presence of PS affected the proliferation of the Israeli acute paralysis virus (IAPV), with no significant difference in the survival rate between the group that received only IAPV and the one that received IAPV and PS in the first 7 days of exposure. Such differences appeared on the sixth and seventh day, and the PS-IAPV group showed reduced survival, as well as the levels of IAPV, began to increase significantly. Histological analyses, in turn, indicated that the exposed individuals had tissue damage in the midgut, which allowed the transport of these particles to the hemolymph, trachea, and Malpighian tubules. The review article by Nowak et al. (2021) discussed the characterization of the microbiota of honeybees and the importance of lactic acid bacteria (LAB) in protecting these animals since much has been discussed about the implementation of probiotics in their food, aiming at improving their health. The other review articles relate the consequences of MPs to the terrestrial ecosystem and its fauna in general. Bouaicha et al. (2022), for example, discussed the possible consequences on the soil and rhizosphere, exemplifying that bees can inadvertently collect MP during their nectar and pollen collections, flight and foraging, and even from the plants they visit. The review by Oliveira et al. (2019) also discusses the transport of MP by bees, warning of the risks of this contamination to the ecosystem service provided through pollination. Büks et al. (2020) warn about how terrestrial fauna can react to microplastic particles, citing that some mining bees can move such particles to the soil while constructing their underground nests. Alterations and reduction in the abundance of several cuticular compounds Ferrante et al. (2024) examined the toxicological effects of polystyrene (PS, 4.8–5.8 µm) and polymethyl methacrylate (PMMA, 1–40 µm), as well as their combination (MIX), on *Apis mellifera* bees. For each treatment, the oral toxicity of three concentrations (0.5, 5, and 50 mg/L) was evaluated in relation to their effects on the immune system and the survival of the workers. Gas chromatography-mass spectrometry (GC–MS) was also employed to investigate whether these particulate matters cause changes in the chemical profile of forages, given that immune activation can lead to alterations in cuticular hydrocarbons. Additionally, a behavioural assay was conducted to determine whether such changes influence the social recognition of bees, potentially compromising the overall integrity of the colony. With respect to food consumption, the results show that rates consistently decreased throughout the test period. Regarding mortality, bees treated with PS and PMMA at high and medium concentrations exhibited faster mortality rates compared to those in the control group. Overall, both particulate matters negatively impacted the survival and immune response of the bees. Additionally, changes in the cuticular profiles (a reduction in the abundance of several compounds) were observed for both MPs at medium and high concentrations, with PMMA showing particularly pronounced effects. Despite the cuticular alterations, the guard bees of the colonies did not prevent the entry of workers exposed to contaminants, showing no increase in the inspection or aggressive behaviour towards them. The exposed bees were treated the same way as unexposed bees. Considering this result, the authors emphasize that this is a crucial point that should be carefully considered in future studies, as it highlights the risk to both individual and colony health. Since contaminated individuals are not “identified” and expelled from the hive, they can more easily spread the particulate matter to other members of the colony. The authors conclude by stressing the urgency of intensifying research efforts to understand the threat that plastic pollution poses to pollinators. Reduction in bee feeding rate and body weight Al Naggar et al. (2023) conducted a study where they chronically exposed Apis mellifera bees (collected in the General Zoology apiary at Martin Luther University Halle-Wittenberg, German), whose gut microbiota was well established, to small (27 ± 17 µm) and large (93 ± 25 µm) polystyrene microplastic (PS-MP) fragments. The bees were exposed to three different concentrations (1, 10, and 100 µg mL−1) for a period of 14 days. Throughout the experiment, the researchers evaluated several factors, including mortality rates, food consumption, and body weight, to determine the impact of these microplastics on the bees. The results of the study indicated that chronic exposure to polystyrene microplastics did not significantly affect the survival of the bees. However, it did lead to a reduction in food consumption and body weight, particularly in the group exposed to the PS-MP solution at a concentration of 10 µg per mL. These findings suggest that while immediate mortality may not be impacted, the reduced food intake and body weight could have long-term detrimental effects on bee health. The authors propose that the irregular shape of the microplastic fragments may contribute to obstructions in the bees’ mouthparts and digestive tract, leading to long-term Leading Article
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