A new study published online in the journal PLoS ONE has found significant contamination of bumblebee pupae by the metal aluminum — a known neurotoxin with links, for example, to Alzheimer’s disease in humans — raising the question of whether Alzheimer’s-like dysfunction is playing a role in the decline of their populations.
The buff-tailed bumblebee (Bombus terrestris). Image credit: Kintaiyo / CC BY 3.0.
The causes of declines in bumblebees and other pollinators remains an on-going debate. While recent attention has focused upon pesticides, other environmental pollutants have largely been ignored.
Aluminum is the Earth’s most ubiquitous ecotoxicant, and the authors of the new study – Prof Chris Exley of Keele University in UK and his colleagues – suggest that it could be a factor in pollinator decline.
The scientists measured the content of aluminum in pupae taken from 20 colonies of naturally foraging buff-tailed bumblebees (Bombus terrestris ssp. audax).
The pupae were found to be heavily contaminated with aluminum, with individual contents ranging from between and 13 and nearly 200 ppm. Smaller pupae had significantly higher contents of aluminum.
“Pupae were heavily contaminated with aluminum giving values between 13.4 and 193.4 μg/g dry wt. and a mean value of 51.0 μg/g dry wt. for the 72 pupae tested,” Prof Exley and co-authors wrote in the study.
To put these aluminum contents in some context, a value of 3 ppm would be considered as potentially pathological in human brain tissue.
While preliminary, these data have shown the significant accumulation of aluminum in at least one stage of the bumblebee life cycle and suggest the possibility of another stressor contributing to the decline in its numbers.
“It is widely accepted that a number of interacting factors are likely to be involved in the decline of bees and other pollinators – lack of flowers, attacks by parasites, and exposure to pesticide cocktails, for example,” Prof Exley said.
“Aluminum is a known neurotoxin affecting behavior in animal models of aluminum intoxication,” he said.
“Bees, of course, rely heavily on cognitive function in their everyday behavior and these data raise the intriguing specter that aluminum-induced cognitive dysfunction may play a role in their population decline – are we looking at bees with Alzheimer’s disease?”
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Exley C et al. Bumblebee Pupae Contain High Levels of Aluminium. PLoS ONE 10 (6): e0127665; doi: 10.1371/journal.pone.0127665
