蜜蜂如何对付合成杀虫剂

A new study reveals how enzymes² in the honey bee gut³ detoxify（使解毒） pesticides⁵ commonly used to kill mites⁷ in the honey bee hive. This is the first study to tease out（梳理） the precise molecular⁸ mechanisms⁹ that allow a pollinating（授粉） insect to tolerate exposure to these potentially deadly compounds. The findings appear in the Proceedings¹⁰ of the National Academy of Sciences.

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Previous studies have shown that honey bee hives are contaminated with an array of agricultural chemicals, many of which the bees themselves bring back to the hive in the form of contaminated pollen¹¹ and nectar（花蜜，甘露） , said University of Illinois entomology（昆虫学） professor and department head May Berenbaum, who led the new research. #

"There are agricultural pesticides everywhere," she said. "They accumulate in the wax of bee hives, so bees in particular are exposed. And their habit of foraging¹² very broadly across a staggering diversity of plant species also tends to expose them to many different types of habitats, which may also have different types of chemical residues¹³（剩余物） ." #

Other chemicals are applied¹⁴ directly to the hives, she said. For the past 20 years, beekeepers have used acaricides（杀螨剂） – chemicals designed to kill mites but not bees – in the hive. #

While evidence so far does not support the idea that exposure to synthetic¹⁵ pesticides is a cause or significant contributor to colony collapse¹⁶ disorder¹⁷, the massive die-off of honey bees first reported in late 2006, "it's abundantly clear that pesticides aren't really very good for any insect," Berenbaum said. "So we figured it was about time somebody knew something about how pollinators process toxins¹⁸."

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The researchers focused on cytochrome P450s, enzymes that are well-known agents of detoxification "in most air-breathing organisms," Berenbaum said. Other studies had shown that cytochrome P450s in honey bees play a key role in their tolerance¹⁹ of pyrethroid pesticides, such as tau-fluvalinate, which is used to kill mites in the hive. But no previous study had identified specific cytochrome（细胞色素） P450s in bees or in other pollinating insects that contribute to pyrethroid tolerance, Berenbaum said.

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In a series of experiments, the team identified three cytochrome P450s in the honey bee midgut that metabolize tau-fluvalinate. They discovered that these enzymes also detoxify coumaphos, a structurally#p#分页标题#e#²⁰ different organophosphate pesticide⁴ that also is used to kill mites in bee hives.

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"This suggests that these honey bee cytochrome P450s are not particularly specialized," Berenbaum said. "That raises the possibility that a nontoxic dose of tau-fluvalinate may become toxic²¹ if an enzyme¹ that is principally involved in its detoxification（解毒） is otherwise occupied with a different chemical." #

The evidence also suggests that honey bees were "pre-adapted" to detoxify pyrethroid pesticides, Berenbaum said. Pyrethroids are similar in structure to naturally occurring defensive²² compounds, called pyrethrins, produced by some flowering plants. Honey bees have likely had a long history of contact with pyrethrins, which are found even in some flowers in the daisy family. It appears that the same enzymes that helped the honey bees detoxify the pyrethrins in nature may also help them tolerate this relatively²³ new pesticide exposure.

The new findings should enhance efforts to develop mite⁶ control methods that are even less toxic to bees, Berenbaum said. #