Re: Gene expression changes in honey bees induced by sublethal imidacloprid exposure
Effects of clothianidin exposure on semen parameters of honey bee drones.
Abstract : Many problems have been reported on honey bees colonies including fertility problems of queens resulted in production failure. Pesticides can be the cause of this failure in connection with the quality of sperm drone. Thus, the aim of this study was to assess the influence of exposure to syrup contaminated with clothianidin at 0.1 µg/L on semen parameters of drones. Results showed a significant decrease of semen volume and sperm concentration and an increase in sperm mortality rate. As for the energetic state, clothianidin increased cell redox potential, the ATP content of spermatozoa as well as the lactate dehydrogenase activity (LDH). It was concluded that exposure to clothianidin during the sexual maturity of drones could affect the semen quality.
https://www.cabdirect.org/cabdirect/abstract/20193066560
Parameterization and sensitivity analysis of a honey bee colony dynamics model for neonicotinoid exposure events using Markov Chain Monte Carlo methods
Abstract
Honey bee (Apis mellifera) colony losses have increased in recent decades in both Europe and North America. While multiple stressors to honey bee colonies appear to be driving this decline (including disease, nutrition, genetics), direct exposure to pesticides has been identified as a factor leading to increased bee declines. The simulation model VarroaPop is currently being modified by the USDA and USEPA to predict honey bee hive dynamics in response to pesticide exposure. However, applying this model to pesticides is complicated due to a lack of parameterization information from the supporting literature for many variables, especially those related to in-hive pesticide dynamics. Here, we utilize data from a field study which measured residues of several neonicotinoid insecticides in pollen and tracked population dynamics of exposed hives to improve our estimation of colony simulation model parameters relevant to VarroaPop and the new model components related to pesticides. We use Markov Chain Monte Carlo methods to sample the probability distribution of model parameters and examine the likelihood of each parameter combination, given the field-derived population data. Through this procedure, we obtain posterior distributions which represent the most likely parameter values given a realistic neonicotinoid exposure scenario. We use these pesticide-optimized parameter distributions to run a global sensitivity analysis for the updated posteriors in order to contrast with a sensitivity analysis based on the priors. This helps determine what factors are most important in driving hive success or failure following exposure events.
https://scholarsarchive.byu.edu/iemssconference/2018/Stream-G/7/
Assessing the Impact of the Conservation Reserve Program on Honey Bee Health
Key Findings (2014–18)
• More than one-sixth of all honey bee yards in North Dakota and South Dakota (the top two honey-producing States) meet the key foraging requirements of honey bees just based on the existence of CRP grasslands alone. Thus, the CRP plays a considerable role in supporting the carrying capacity of honey bee colonies in this region (Otto and others, 2018).
• Honey bee colonies in areas surrounded by grassland, such as those enrolled in the CRP, are 10–15 percent larger than colonies kept in areas surrounded by mostly row crops. A USGS study determined that a bee yard surrounded by mostly grassland can yield an extra $4,100 in annual revenue to a beekeeper compared to a bee yard surrounded by mostly row crop. A beekeeper who manages several hundred bee yards may incur sizable economic gains through nearby CRP and other conservation grass- lands (Smart and others, 2018).
• The USGS led the first large-scale assessment of native bees on CRP grassland that documented what native bees were present on CRP grasslands and what flowers they used (Otto and others, 2017).
• The USGS developed a genetic sequencing strategy to rapidly quantify pollen grains collected from bees (Smart and others, 2017). This novel technique allowed the USGS to determine what flowering plants were impor- tant bee food. Knowing what flowers constitute good
bee food is an important step in improving the cost- effectiveness of the CRP.
• The USGS launched the “Pollinator Library,” a decision- support tool that can be used by USDA staff for evalu- ating seeding mixes for the CRP (
https://www.npwrc. usgs.gov/pollinator/). This website provides users with information on which plants are favored by honey bees and native bees. USGS scientists published a paper demonstrating how USDA staff can use the Pollinator Library to evaluate the cost-effectiveness of CRP seeding mixes (Otto and others, 2017).
https://pubs.usgs.gov/fs/2018/3082/fs20183082.pdf
Hazard of a neonicotinoid insecticide on the homing flight of the honeybee depends on climatic conditions and Varroa infestation
Abstract
The paradigm for all toxicological bioassays in the risk assessment of pesticide registration reflects the principle that experimental conditions should be controlled to avoid any other factors that may affect the endpoint measures. As honeybee colonies can be frequently exposed to bio-aggressors in real conditions, often concomitantly with pesticides, co-exposure to pesticide/bio-aggressors is becoming a concern for regulatory authorities. We investigated the effects of the neonicotinoid insecticide thiamethoxam on the homingperformances of foragers emerging from colonies differentiated by health status (infestation with Varroa destructor mites, microsporidian parasite Nosema spp. and Deformed Wing Virus). We designed a homing test that has been recently identified to fill a regulatory gap in the field evaluations of sublethal doses of pesticides before their registration. We also assessed the effect of temperature as an environmental factor. Our results showed that the Varroa mite exacerbates homing failure (HF) caused by the insecticide, whereas high temperatures reduce insecticide-induced HF. Through an analytical Effective Dose (ED) approach, predictive modeling results showed that, for instance, ED level of an uninfested colony, can be divided by 3.3 when the colony is infested by 5 Varroa mites per 100 bees and at a temperature of 24 °C. Our results suggest that the health status of honeybee colonies and climatic context should be targeted for a thorough risk assessment.
https://www.sciencedirect.com/science/article/pii/S0045653519303534