The sad story of the bee
Across the world, there are over 20,000 different species of bee, including the infamous honeybee, the Ashy mining bees and the Megachile pluto – the world’s largest bee measuring an incredible 4 cm in length. Sadly, the story of bees over the past century has been one of rapid decline. Natural Agricultural Statistics show a reduction in honey bee numbers from approximately 6 million hives in 1947 to 2.4 million hives in 2008; a staggering 60% drop.
Greenpeace suggest that the decline in bee populations is attributed to several factors, including but not limited to:
• Habitat destruction
• Nutrition deficit
• Air pollution
• Global warming
Of these factors, the two most prominent causes are pesticides and habitat loss. It is therefore a sad reality that that the human species is largely accountable for the declining number of bees across the world. So, what can we do to save them?
Looking at the molecular effect of pesticides on gene expression
One group of scientific researchers are demanding improved regulation on pesticides. This comes after their research study, published today in Molecular Ecology, found that pesticides affect genes in bumblebees which may be involved in a broad range of biological processes.
The research project, led by Queen Mary University of London in collaboration with Imperial College London, applied a biomedical approach to investigate changes in the bumble genome after pesticide exposure.
The scientists exposed colonies of bumblebees to clothianidin or imidacloprid, “neonicotinoid” pesticides that are unfortunately still used worldwide, at field-realistic concentrations. For worker bumblebees, the activity levels of 55 genes were altered by exposure to clothianidin. 31 genes showed higher activity levels, while the rest showed lower activity levels. The scientists note that this may indicate their bodies are attempting to detoxify, resulting in gene expression changes to reorienting resources required for biological mechanisms.
In contrast, queen bumblebees were found to have changed activity levels in 17 genes, of which 16 were more greatly expressed after exposure to clothianidin. Joe Colgan, first author of the study, said in a recent press release: "This shows that worker and queen bumblebees are differently wired and that the pesticides do not affect them in the same way. As workers and queens perform different but complementary activities essential for colony function, improving our understanding of how both types of colony member are affected by pesticides is vital for assessing the risks these chemicals pose."
Their findings support those of previous studies, including research by the same authors, that show even low doses of neurotoxic pesticides can impair bee behaviors, such as their ability to gather pollen and nectar from flowers, and the ability to locate their nests.
Improving pesticide regulation
Lead author of the study, Yannick Wurm, stated: "Governments had approved what they thought were “safe” levels, but pesticides intoxicate many pollinators, reducing their dexterity and cognition and ultimately survival. This is a major risk because pollinators are declining worldwide yet are essential for maintaining the stability of the ecosystem and for pollinating crops.”
Colgan added: "We examined the effects of two pesticides on one species of bumblebee. But hundreds of pesticides are authorized, and their effects are likely to substantially differ across the 200,000 pollinating insect species which also include other bees, wasps, flies, moths, and butterflies."
The research group encourage others to adopt their approach to studying the impact of pesticides at the molecular level. "Our work demonstrates that the type of high-resolution molecular approach that has changed the way human diseases are researched and diagnosed, can also be applied to beneficial pollinators. This approach provides an unprecedented view of how bees are being affected by pesticides and works at large scale. It can fundamentally improve how we evaluate the toxicity of chemicals we put into nature,” commented Wurm.
Caste- and pesticide-specific effects of neonicotinoid pesticide exposure on gene expression in bumblebees. 2019. Thomas J. Colgan, Isabel K. Fletcher, Andres N. Arce, Richard J. Gill, Ana Ramos Rodrigues, Eckart Stolle, Lars Chittka and Yannick Wurm. Molecular Ecology.