Biomarker responses and lethal dietary doses of tau-fluvalinate and coumaphos in honey bees: Implications for chronic acaricide toxicity

Enhanced immune response and antimicrobial activity in honey bees (Apis mellifera) following application of oxalic acid-glycerine strips

Bee health is influenced by multiple factors, including nutrition, immunity, and parasitic pressures. Since the spread of Varroa destructor, overwintering survival has significantly declined, making it one of the most serious threats to honey bee (Apis mellifera L.) populations worldwide. Natural acaricides, such as oxalic acid (OA), are widely employed for managing Varroa mites; however, their pharmacodynamics, particularly their impacts on honey bee physiology and immunity, remain insufficiently understood. We studied effects of oxalic acid on honey bee workers. The study compared three treatments: flumethrin, OA-glycerine strips (OA-G), and OA trickling (OA-T). Twelve colonies were divided into four groups, with samples collected at five time points (0, 24, 48, 72, and 192 h). Physiological changes were assessed through markers of oxidative stress, longevity, and immune parameters. Exposure to oxalic acid via glycerine strips induced a humoral immune response in adult bees. The antimicrobial activity of hemolymph and levels of antimicrobial peptides (abaecin, apidaecin, defensin, and hymenoptaecin) were elevated between 48 and 192 h after OA-G treatment compared to the control group. In contrast, these parameters were not influenced by OA-T or flumethrin treatment. These findings suggest that OA-G strips activate the honey bee's immune system, providing insights into broader implications of OA use in beekeeping. It is crucial to determine whether the activation of humoral immune systems has positive or negative effects, as well as to develop standardized and reliable treatment protocols that ensure both - health of colonies and their effectiveness in controlling Varroa mite infestations.

Effects of anthropogenic stress on stingless bees Melipona mandacaia inhabiting urban and natural environments

Bees play a crucial role as pollinators, significantly contributing to ecosystem health. However, they face growing threats from human activities. This study uses biomarkers to evaluate the health status of Melipona mandacaia, a stingless bee native to the Caatinga biome, as indicators of anthropogenic stress. Bees were collected from the unique Caatinga biome, which had no recorded human pressure, and from an urban area with high human pressure. These bees were then analyzed for various biomarkers to assess the different levels of anthropogenic stress. The biomarkers included cholinesterases (ChE) to assess neurotoxicity, catalase (CAT) to measure antioxidant responses, glutathione S-transferases (GST) for detoxification pathways, and lipid peroxidation (LPO) as an indicator of oxidative stress. The results reveal that ChE inhibition may be associated with stress levels due to human activities showing an inhibition pattern with increased stress levels (up to 54.4 % inhibition), while the remaining biomarkers showed mixed responses across the different stress-level areas. In addition, the use of a principal component analysis (PCA) allowed a separation between the different groups and the weigh of the measured variables to each anthropogenic stress group. The integrated biomarker response (IBR) index was applied showing a clear distinction among groups. The obtained results could be partly explained by the beekeeping practices in some locations, which may have mitigated the effects of anthropogenic stressors to a certain degree, especially in HS. These findings underscore the importance of monitoring wild bee health in the Caatinga and demonstrate the value of a multifaceted biomarker approach for understanding the impacts of anthropogenic stressors on bee populations in varied environments and the effects of beekeeping.

Storage Conditions of Sperm Samples and Gametic Characterization by Sperm Head Morphometry in Drones (Apis mellifera)

The present study aimed to evaluate an optimal method to transport and store drone sperm samples, as well as to characterize drone spermatozoa through sperm head morphometry. A total of 291 mature drones were used. We performed three experiments. In a first experiment, sperm variables were assessed under different incubation conditions (5 °C, 15 °C, and 37 °C with 5% CO2). Results showed that sperm viability was optimally maintained at 15 °C (p ˂ 0.05). In the second experiment, the supplementation of extender with catalase (200 UI) improved (p ˂ 0.05) the sperm viability and motility during liquid storage at different incubation times. Finally, a morphometric analysis of sperm head was made: length 5.13 µm, width 0.85 µm, area 3.78 µm2, perimeter 15.01 µm, acrosome length 3.50 µm. The variability in sperm head morphometry was calculated by coefficients of variation (CV) within- and between-drones. The CV within-drone was higher than the CV between-drones for all morphometric parameters regardless of hive origin, indicating a high degree of sperm pleomorphism.

Unveiling Molecular Mechanisms Mediating Coumaphos Tolerance in Western Honey Bees (Apis mellifera)

Honey bees (Apis mellifera) are managed pollinators playing a critical role in global agriculture. Among factors linked to bee decline, the ectoparasitic varroa mite (Varroa destructor) is a major stressor. Coumaphos is an organophosphate pro-insecticide known for its selectivity toward honey bees, rendering it an effective in-hive treatment against varroa mites. This study investigated the molecular mechanisms underlying coumaphos tolerance in honey bees. Coumaphos-oxon inhibition studies with recombinantly expressed acetylcholinesterases of bees and mites precluded toxicodynamic reasons for the observed selectivity. Synergist bioassays and biochemical studies confirmed that honey bee CYP9Q2 is a key enzyme involved in coumaphos detoxification, particularly by its catalytic capacity to hydroxylate coumaphos-oxon. Bioassays with transgenic Drosophila expressing CYP9Q2 validated our molecular findings. Enzyme inhibition studies revealed suicide substrate properties for coumaphos leading to the inactivation of P450s during coumaphos oxidation. This study demonstrated the complexity of P450-mediated coumaphos activation and inactivation driving honey bee selectivity.