Through funding from the British Ecological Society, we were able to further analyse the honeybees collected during 2021, to investigate the impact of air quality on honeybee eye structure. The aim of the project was to determine whether the diameter of ommatidia facets of honeybee compound eyes was correlated with levels of PM2.5 in sampled air.
We randomly selected six honeybees (three nurse bees and three forager bees) from 12 hives from areas of both high particulate matter (12-25 µg/m3) and low particulate matter (0-11µg/m3) (a total of 72 bees). The bees were examined using a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray (EDX) detector and a digital camera. Images were taken of honeybee eyes at 1000x magnification, and in each image, the diameter of five randomly selected ommatidia measured, to enable the calculation of the mean ommatidia diameter for each bee at each site.
We found that ommatidium diameter was significantly smaller in honeybees sampled in areas of high air particulate concentration when compared with those sampled in area of low particulate concentration. Ommatidium diameter was negatively correlated with levels of PM10, PM2.5 and PM1.
These findings suggest that honeybees in areas with higher airborne particulate matter concentrations may face additional challenges when foraging, as ommatidium diameter is known to play a role in object identification and vision in low light conditions. However, although diameter plays a role, the inter-ommatidial angle also affects the ability to resolve fine-grained images and our next step is to process the samples again, measuring the inter-ommatidial angles.
Follow up research is necessary to determine whether the changes we observed in the eye affects foraging through behavioural tests and to confirm the results under laboratory conditions. The results from Thriving Hive indicate that more honey is produced in areas of higher air quality – is this related to honeybee foraging ability? This is an open question.
