Biology subjects

Bajorek, D.

Publications and source records attributed to Bajorek, D..

5 recordsLinked to original sources

bioRxiv2026

Dietary ethanol produces endpoint-specific dose responses in honeybees

Ethanol is naturally present in nectar, but we still know little about how pollinators cope with long-term exposure to it at low concentrations. We exposed adult worker honeybees (Apis mellifera carnica Poll.) for eight days to diets containing 0, 0.1, 0.5, 1, 2, or 10% ethanol and measured survival, estimated intake, open-field locomotion, sting extension, whole-body trehalose, and hemolymph ethanol. Hemolymph ethanol was correlated with dietary concentration, attesting to internal exposure. Survival differed among diets, an effect which was driven by the difference between the 10% ethanol treatment and the control. Food intake was lowest at the 10% ethanol diet. There was also a modest increase in intake under the 0.1% ethanol treatment. In terms of locomotor features, bees moved less, moved more slowly, explored less space, covered shorter distances, and followed more tortuous paths after the 10% ethanol treatment. Neither sting extension nor trehalose were affected by dietary ethanol. The results showed no beneficial stimulation at lower concentrations. Instead, performance was endpoint-specific: at 0.1-2% ethanol in the diet, performance remained relatively stable across most parameters, whilst clear impairment was evident at 10%. These findings highlight resilience to repeated ethanol exposure in honeybees.

animal behavior and cognition↗

bioRxiv2025

Honeybees show an increased preference for dietary alcohol when parasitized

Parasitic infections often alter host behavior, including foraging and the consumption of bioactive substances. In honeybees (Apis mellifera), infection with the common gut parasite Nosema ceranae causes metabolic disruption and increased mortality. Ethanol is a naturally occurring bioactive compound found in nectar, and honeybees exhibit high tolerance and resilience to chronic exposure. However, whether bees actively use ethanol during infection remains unclear. Here, we investigated whether N. ceranae-infected honeybees alter their ethanol consumption. In a feeding experiment, infected and uninfected bees were given a choice between plain sucrose solution and ethanol-spiked food (0.5% or 1% ethanol). We measured food consumption, survival, and spore load. Although overall food intake did not differ between groups, infected bees consumed a significantly higher proportion of ethanol-spiked food. Survival analysis showed that a diet containing 1% ethanol caused higher mortality than a diet containing 0.5% ethanol; however, among bees on a 1% ethanol diet, this negative effect was less pronounced in infected individuals than in controls. Spore load did not differ between treatments. These results suggest that N. ceranae infection induces a shift in feeding behavior towards increased ethanol intake, which may benefit infected bees by reducing mortality. This may reflect a self-medication response, although alternative explanations - such as parasite-induced manipulation or ethanol-induced changes in host physiology and immunity - remain possible. Further research into ethanols effects on Nosema spores is needed. Nonetheless, our findings provide insights into honeybee interactions with bioactive compounds and suggest that ethanol may be a behaviorally relevant dietary substance.

pathology↗

bioRxiv2025

Meta-analysis and experimental evidence reveal no impact of Nosema ceranae infection on honeybee carbohydrate consumption

Honeybees (Apis mellifera) are indispensable pollinators, essential for ecosystem stability and agricultural productivity. However, they face numerous challenges, including pathogens that threaten their survival and ecosystem services. Among these pathogens, Nosema ceranae, a microsporidian parasite, causes significant damage to the intestinal tract and induces energetic imbalances in an organism, posing a major threat to both individual bees and entire colonies. In response to infections, bees often engage in behavioural defenses, such as selecting foods with higher antibiotic properties. We hypothesized that bees infected with N. ceranae might compensate behaviourally by increasing their carbohydrate consumption. To test this hypothesis, we conducted a meta-analysis of existing studies comparing sugar consumption in healthy and infected bees, complemented by an experimental study. In our experiment, we measured sugar intake and quantified trehalose levels in the hemolymph, a key indicator of energy reserves. Both the meta-analysis and experimental results consistently showed no significant differences in sugar consumption between healthy and infected bees. Similarly, trehalose levels in the hemolymph remained comparable between the two groups. Our findings suggest that the infection caused by N. ceranae does not elicit compensatory feeding behavior in honeybees. Moreover, the meta-analysis revealed significant gaps in current research, particularly a lack of studies focusing on forager bees, which face the highest energetic demands among colony members. Our findings call for future studies on the energetic effects of nosemosis and studies conducted under natural or semi-natural conditions.

pathology↗

bioRxiv2024

Honey bees are resilient to the long-term presence of alcohol in their diet

Previous studies on various organisms have suggested that low doses of ethanol can have stimulatory effects, while higher doses may lead to toxicity, a response known as hormesis. Low ethanol concentrations occur naturally in the environment, particularly in fermenting fruits and flower nectar, where pollinators such as honey bees may encounter it. This study aimed to investigate the potential hormetic effects of low-level ethanol consumption on honey bees. Bees were divided into three groups: one provided with only sucrose solution, one both with sucrose and 0.5% ethanol in sucrose, and one with only 1% ethanol in sucrose. The bees were exposed to these diets for 14 days, and their performance was assessed through survivorship, flight endurance, body mass, lipid content, and trehalose and ethanol levels in the haemolymph. The results showed no significant differences in most parameters between the groups. However, bees constantly exposed to 1% ethanol had slightly higher trehalose levels compared to the control group, suggesting a possible adaptive response to ethanol exposure. Ethanol levels in the haemolymph differed significantly between groups, with bees exposed to ethanol showing its detectable levels in their system. While no clear hormetic effects were observed in terms of improved performance, the elevated trehalose levels in bees constantly exposed to 1% ethanol may indicate adaptations protecting from ethanol-induced damage. The study provides insights into how honey bees tolerate low-level ethanol exposure and highlights the need for further research on the ecological implications of ethanol consumption in pollinators.

physiology↗

bioRxiv2024

Occasional and constant exposure to dietary ethanol shortens the lifespan of worker honey bees

Honey bees (Apis mellifera) are one of the most crucial pollinators, providing vital ecosystem services. Their development and functioning depend on essential nutrients and substances found in the environment. While collecting nectar as a vital carbohydrate source, bees routinely encounter low doses of ethanol from yeast fermentation. Yet, the effects of repeated ethanol exposure on bees survival and physiology remain poorly understood. Here, we investigate the impacts of constant and occasional consumption of food spiked with 1% ethanol on honey bee mortality and alcohol dehydrogenase (ADH) activity. This ethanol concentration might be tentatively judged close to that in natural conditions. We conducted an experiment in which bees were exposed to three types of long-term diets: constant sugar solution (control group that simulated conditions of no access to ethanol), sugar solution spiked with ethanol every third day (that simulated occasional, infrequent exposure to ethanol) and daily ethanol consumption (simulating constant, routine exposure to ethanol). The results revealed that both constant and occasional ethanol consumption increased the mortality of bees, but only after several days. These mortality rates rose with the frequency of ethanol intake. The ADH activity remained similar in bees from all groups. Our findings indicate that exposure of bees to ethanol carries harmful effects that accumulate over time. Further research is needed to pinpoint the exact ethanol doses ingested with food and exposure frequency in bees in natural conditions.

physiology↗