Ethanol Hormesis in Honeybees (Apis mellifera L.) Infected with Vairimorpha (Nosema) spp

TL;DR

Low ethanol exposure can improve honeybee lifespan and reduce parasite severity, but higher amounts are harmful.

Contribution

Demonstrates ethanol hormesis in honeybees infected with Vairimorpha (Nosema) spp.

Findings

Low ethanol concentrations (0.625% and 1.25%) extended lifespan and reduced parasite burden in infected bees.

Higher ethanol concentrations (2.5% and above) increased mortality and parasite load.

Ethanol effects depend on infection status and concentration, suggesting a hormetic response.

Abstract

This study examined honeybees to test ethanol hormesis in the context of Vairimorpha (Nosema) spp. infection. It explored whether small amounts of ethanol could mitigate infection effects and influence lifespan. The results showed a biphasic response: low to moderate ethanol exposure extended lifespan and aligned with reduced Vairimorpha spp. severity in infected bees, consistent with hormesis. In contrast, higher ethanol exposure was toxic, increasing mortality and parasite burden. Overall, the results suggest that trace ethanol exposure—similar to what bees may encounter in nectar—can differentially affect bee health based on infection status, highlighting nuanced associations among diet, infection, and longevity.

This study investigates the phenomenon of ethanol hormesis in honeybees (Apis mellifera) infected with Vairimorpha (Nosema) spp., a widespread parasite that significantly impacts bee health and colony survival. Hormesis refers to a biphasic response where low doses of potentially harmful substances may elicit beneficial effects, contrasting with the detrimental impacts observed at higher concentrations. We hypothesized that low ethanol concentrations could reduce Vairimorpha spp. infection severity and improve bee lifespan. In a controlled experiment, foraging bees were divided into groups of infected and uninfected individuals, and each group (N = 50) was exposed to varying ethanol concentrations (0%, 0.0313%, 0.625%, 1.25%, 2.5%, 5%, and 10%). The results indicated that infected bees exposed to 0.625% and 1.25% ethanol exhibited the longest lifespans and the lowest Vairimorpha (Nosema) spp. spore counts, supporting the hormetic model. In contrast, higher ethanol concentrations (2.5% and above) significantly increased mortality and spore load, reaffirming the toxic effects associated with excessive ethanol intake. This study highlights the complex interactions between ethanol exposure and parasitic infection in honeybees, suggesting that ethanol at 0.625% and 1.25% may mitigate some of the harmful effects of Vairimorpha (Nosema) spp. infections. The findings have implications for understanding how ethanol, present in floral nectar, impacts honeybee health and could inform management strategies for controlling Vairimorpha (Nosema) spp. infections in bee populations.

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