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ARS Home » Pacific West Area » Tucson, Arizona » Carl Hayden Bee Research Center » Research » Publications at this Location » Publication #320467
Title: The fungicide Pristine® inhibits mitochondrial function in vitro but not flight metabolic rates in honey bees

Author
item NATH, RACHNA - Arizona State University
item CAMPBELL, JACOB - Arizona State University
item GADAU, JUERGEN - Arizona State University
item FOX, TREVOR - Arizona State University
item DeGrandi-Hoffman, Gloria
item HARRISON, JON - Arizona State University

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2015
Publication Date: 12/10/2015
Citation: Nath, R., Campbell, J., Gadau, J., Fox, T., Hoffman, G.D., Harrison, J. 2015. The fungicide Pristine® inhibits mitochondrial function in vitro but not flight metabolic rates in honey bees. Journal of Insect Physiology. 86:11-16.

Interpretive Summary: Honey bees can be exposed to fungicides during pollination because these pesticides can be applied while crops are in bloom. Unlike insecticides that affect neurological function, fungicides disrupt or inhibit fundamental cellular processes such as respiration. The biochemical pathways affected by fungicides are similar across species so that the modes of action for fungicides might have analogous biochemical or physiological effects on non-fungal organisms such as bees. We tested the effects of the fungicide Pristine® on mitochondrial activity in honey bees. This fungicide reduces fungal growth by inhibiting certain mitochondrial functions. We found that direct exposure of mitochondria to Pristine® levels above 5 ppm strongly inhibited honey bee mitochondrial oxidation rates in vitro. However, bees that consumed pollen containing Pristine® at ecologically-realistic concentrations (˜1 ppm) had normal flight CO2 emission rates and thorax temperatures. Mitochondria isolated from the flight muscles of bees that consumed pollen with Pristine® had higher state 3 oxygen consumption rates than control bees, suggesting that Pristine® consumption might cause compensatory changes in mitochondria function. It is likely that the lack of a strong functional effect of Pristine® consumption on flight performance and the in vitro function of flight muscle mitochondria results from maintenance of Pristine® levels in the flight muscles at much lower levels than occur in the food, perhaps due to metabolism and detoxification. As Pristine® has been shown to negatively affect feeding rates and protein digestion of honey bees, it is plausible that Pristine® consumption might negatively affects gut wall function where mitochondria may be exposed to higher concentrations of this fungicide.

Technical Abstract: Honey bees and other pollinators are exposed to fungicides that act by inhibiting mitochondrial function. Here we test whether a common fungicide (Pristine®) inhibits the function of mitochondria of honeybees, and whether consumption of ecologically-realistic concentrations can cause negative effects on the mitochondria of flight muscles, or the capability for flight, as judged by CO2 emission rates and thorax temperatures during flight. Direct exposure of mitochondria to Pristine® levels above 5 ppm strongly inhibited honey bee mitochondrial oxidation rates in vitro. However, bees that consumed pollen containing Pristine® at ecologically-realistic concentrations (˜1 ppm) had normal flight CO2 emission rates and thorax temperatures. Mitochondria isolated from the flight muscles of the Pristine®-consuming bees had higher state 3 oxygen consumption rates than control bees, suggesting that possibly Pristine®-consumption caused compensatory changes in mitochondria. It is likely that the lack of a strong functional effect of Pristine® consumption on flight performance and the in vitro function of flight muscle mitochondria results from maintenance of Pristine® levels in the flight muscles at much lower levels than occur in the food, probably due to metabolism and detoxification. As Pristine® has been shown to negatively affect feeding rates and protein digestion of honey bees, it is plausible that Pristine® consumption negatively affects gut wall function (where mitochondria may be exposed to higher concentrations of Pristine®); alternatively, Pristine® may negatively affect bees by affecting their gut microbiota.