The molecular impacts of chronic pesticide exposure on bee learning and memory

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Background: Recently, concern has been raised regarding the impact of a common class of pesticide known as neonicotinoids on honey bees and native bee pollinators. These neonicotinoids are widely used as seed treatments in agriculture. However, it is unclear whether neonicotinoids have a significant lethal or sub-lethal effect on bees at realistic field levels. There is a growing concern regarding chronic exposure to neonicotinoids through nectar, pollen, and water picked up by foraging bees and carried back to the hive. Chronic exposure can disrupt bees' reproduction, mobility, navigation, feeding, foraging, memory, learning, and overall hive activity. These chemicals are also suspected of affecting the honey bees' immune systems, making them more vulnerable to parasites and pathogens. Another key suspect in the recent decline of honey bee colonies is the parasitic mite Varroa destructor. It has become the most serious pest for the European honey bee Apis mellifera, which lacks natural defences to be able to deal with the mite. The mite also vectors of a number of viruses which can dramatically affect colony health, and is now recognised as one of the primary causes of honey bee decline. In order to control varroa, beekeepers apply chemical varroacides to infected hives. Several products are registered in the UK including Oxalic acid, Thymol, formic acid, two pyrethroid insecticides - tau-fluvalinate and flumethrin, and a proprietary blend consisting of Camphor Racemic, Eucalyptus Oil, Menthol Levo, Thymol. Additionally, Coumaphos and Amitraz are registered for use in the USA. There is evidence that some of these chemicals are hazardous to bees and contribute to bee decline, and as with the neonicotinoids may have significant impact on the bees homing ability and foraging rates. Amitraz has also been cited as a synergist that amplifies the toxic effects of pyrethroids and neonicotinoids. Experimental approaches: This project will examine the sub-lethal effects of bee hive chemicals on bee mobility, navigation, memory and learning. These experiments will be conducted using a novel thermal-visual arena place learning assay platform, where bees must find a hidden 'safe' target (that is a cool tile) in an otherwise unappealing warm environment, using available spatial cues on the walls of the arena. The effects of low dose pesticide application on the ability to learn and return to the safe zone will be assessed using proprietary tracking software, whereas the sub-lethal effects of pesticides on short and long term memory will be assessed by studying the direct effects on the bees memory pathways, which are relatively well characterised at the biochemical and molecular level. Training: The techniques and facilities for carrying out this research are available at Rothamsted and the student will work alongside other graduate students and post-docs. The student will develop bioinformatics skills relating to bee genomes, will become conversant with standard molecular techniques (PCR, gel electrophoresis etc) that are widely applicable and will also benefit from learning more specialised techniques e.g, insect behaviour assays, pesticide application techniques etc). The student will also participate in the Institutes extensive postgraduate training programme.