Diesel exhaust pollution affects learning abilities and leads to an altered stress response in the CNS of the honey bee (Apis mellifera)

Diesel exhaust pollution affects learning abilities and leads to an altered stress response in the CNS of the honey bee (Apis mellifera)

Question: Diesel Exhaust Pollution (DEP) is known to be detrimental to individuals with asthma and cardiovascular diseases [1]. Epidemiological, and mammalian in vivo and in vitro studies demonstrate that DEP also affects the Central Nervous System (CNS) [2]. Despite efforts to improve air quality, DEP persists as a problem and the share of diesel engined passenger cars in Western Europe is increasing steadily.

Honey bees are an important pollinator of food crops and wild flowering plants. They not only contribute to food security by providing pollination services of an enormous economic value but also play an important ecological role. Over the last five years, bee keepers world-wide have reported a decline in honey bee populations. The reasons for this decline remain unknown, but it is thought to be multi-factorial [3]. Honey bee colonies are confronted with a number of stressors, for example infection with the mite Varroa destructor or exposure to pesticides. To forage successfully honey bees rely on their learning and memory abilities. Our research aims to establish whether DEP might be a factor contributing to declines in honey bee populations through impairment of healthy CNS function.

Methods: We have investigated the impact of DEP exposure on the learning abilities of the honey bee using the proboscis extension reflex and classical conditioning. Western blotting and histology were used to determine regional expression levels of stress proteins in the brain in response to an acute diesel exhaust exposure. We are examining the morphological appearance of glial cells to investigate the impact of DEP in the honey bee CNS of DEP exposed, and control, forager bees.

Results and Conclusions: We hypothesize that DEP acts as a stressor in the brain of the honey bee causing changes in glial cells that are detectable using morphological and molecular techniques – similar to microglial activation or immunological responses of astroglia in the mammalian brain. This work will further our understanding of how DEP acts on the brain and how it might impact on the health of the animal. Current results indicate that diesel exhaust pollution impacts on the neurobiology of the honey bee and this may contribute to decline by impairing CNS functions.

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