The mechanisms that underpin aging are still elusive. In this study, we suggest that the ability of mitochondria to oxidize different substrates, which is known as metabolic flexibility, is involved ...in this process. To verify our hypothesis, we used honey bees (Apis mellifera carnica) at different ages, to assess mitochondrial oxygen consumption and enzymatic activities of key enzymes of the energetic metabolism as well as ATP5A1 content (subunit of ATP synthase) and adenylic energy charge (AEC). We also measured mRNA abundance of genes involved in mitochondrial functions and the antioxidant system. Our results demonstrated that mitochondrial respiration increased with age and favored respiration through complexes I and II of the electron transport system (ETS) while glycerol‐3‐phosphate (G3P) oxidation was relatively decreased. In addition, glycolytic, tricarboxylic acid cycle and ETS enzymatic activities increased, which was associated with higher ATP5A1 content and AEC. Furthermore, we detected an early decrease in the mRNA abundance of subunits of NADH ubiquinone oxidoreductase subunit B2 (NDUFB2, complex I), mitochondrial cytochrome b (CYTB, complex III) of the ETS as well as superoxide dismutase 1 and a later decrease for vitellogenin, catalase and mitochondrial cytochrome c oxidase subunit 1 (COX1, complex IV). Thus, our study suggests that the energetic metabolism is optimized with aging in honey bees, mainly through quantitative and qualitative mitochondrial changes, rather than showing signs of senescence. Moreover, aging modulated metabolic flexibility, which might reflect an underpinning mechanism that explains lifespan disparities between the different castes of worker bees.
Ontogeny of the energetic metabolism in honey bees and the underpinning metabolic flexibility: Aging has beneficial effects on the energetic metabolism of honey bees, i.e., it increases mitochondrial respiration (mainly sustained by succinate and glycerol‐3‐phosphate oxidation) and enzymatic activities. This is backed by an augmentation in ATP5A1 (ATPsynthase subunit) content. The increment of these markers leads to an overall optimization of the energetic output of mitochondria that is indicated by an increase in the adenylic energy charge in aged workers.
The decline of pollinators worldwide is of growing concern and has been related to the use of plant-protecting chemicals. Most studies have focused on three neonicotinoid insecticides (clothianidin, ...imidacloprid, and thiamethoxam) currently subject to a moratorium in the EU. Here, we focus on thiacloprid, a widely used cyano-substituted neonicotinoid thought to be less toxic to honey bees and of which use has increased in the last years. Honey bees (Apis mellifera carnica) were exposed chronically to thiacloprid in the field for several weeks at a sublethal concentration. Foraging behavior, homing success, navigation performance, and social communication were impaired, and thiacloprid residue levels increased both in the foragers and the nest mates over time. The effects observed in the field were not due to a repellent taste of the substance. For the first time, we present the necessary data for the risk evaluation of thiacloprid taken up chronically by honey bees in field conditions.
The current status of Nosema spp. infections in A. mellifera throughout Eurasia was characterized using electronic databases. Although N. ceranae was predominantly detected in southwestern and ...south-central regions and N. apis in northwestern and north-central areas, most studies reported the occurrence of both species in Eurasia. In addition, the occurrence of Nosema spp. and Ptp3 gene haplotypes was investigated in the Republic of Tatarstan, Russia. Most of the examined honey bees were infected with both N. apis and N. ceranae. N. apis and N. ceranae isolates were either heterozygous or belonged to different strains and showed infection with more than one strain. New haplotypes were found for N. apis and N. ceranae in the Republic of Tatarstan, Russia. This study expands the data regarding existing haplotypes of Nosema species: there are currently 9 shared and 56 unique Ptp3 nucleotide sequence haplotypes of N. ceranae, and 2 shared and 7 unique haplotypes of N. apis, respectively.
Mitochondria have been suggested to be paramount for temperature adaptation in insects. Considering the large range of environments colonized by this taxon, we hypothesized that species surviving ...large temperature changes would be those with the most flexible mitochondria. We thus investigated the responses of mitochondrial oxidative phosphorylation (OXPHOS) to temperature in three flying insects: the honeybee (
), the fruit fly (
) and the Colorado potato beetle (
). Specifically, we measured oxygen consumption in permeabilized flight muscles of these species at 6, 12, 18, 24, 30, 36, 42 and 45°C, sequentially using complex I substrates, proline, succinate, and glycerol-3-phosphate (G3P). Complex I respiration rates (CI-OXPHOS) were very sensitive to temperature in honeybees and fruit flies with high oxygen consumption at mid-range temperatures but a sharp decline at high temperatures. Proline oxidation triggers a major increase in respiration only in potato beetles, following the same pattern as CI-OXPHOS for honeybees and fruit flies. Moreover, both succinate and G3P oxidation allowed an important increase in respiration at high temperatures in honeybees and fruit flies (and to a lesser extent in potato beetles). However, when reaching 45°C, this G3P-induced respiration rate dropped dramatically in fruit flies. These results demonstrate that mitochondrial functions are more resilient to high temperatures in honeybees compared to fruit flies. They also indicate an important but species-specific mitochondrial flexibility for substrate oxidation to sustain high oxygen consumption levels at high temperatures and suggest previously unknown adaptive mechanisms of flying insects' mitochondria to temperature.
The Carniolan honey bee (Apis mellifera carnica) is an indigenous subspecies of the Western honey bee in Central Europe. Croatia represents a large part of its native range. Hybridization and ...introgression is a realistic possibility due to unmonitored imports by beekeepers. In this study, we focused on honey bee colonies managed by beekeepers from all over Croatia and Slovenia. The identification of the subspecies was based on wing geometric morphometrics. The similarity of all investigated colonies to A. m. carnica was substantial, which indicates that the native subspecies continues to be present in the study area. However, some of the colonies differed markedly from the currently available reference of this subspecies. The low similarity with reference samples can be related both to hybridization with non-native subspecies and to natural geographical variation within A. m. carnica. The data and results obtained from this morphometric analysis will provide a deeper insight into the phenotypic characterization of the studied honey bee populations and directions for future conservation strategies.
Trace sensing of explosive vapours is a method in humanitarian demining and Improvised Explosive Device (IED) detection that has received increasing attention recently, since accurate, fast, and ...reliable chemical detection is highly important for threat identification. However, trace molecule sampling in the field can be extremely difficult due to factors including weather, locale, and very low vapour pressure of the explosive. Preconcentration of target molecules onto a substrate can provide a method to collect higher amounts of analyte for analysis. We used the commercial fluoropolymer Aflas as a preconcentrator material to sorb explosive molecules to the surface, allowing subsequent detection of the explosives via the luminescence quenching response from the organic polymer Super Yellow. The preconcentration effect of Aflas was confirmed and characterised with 2,4-DNT, prior to field sampling being conducted at a test minefield in Croatia by placing preconcentration strips in the entrance of beehives, where honeybees have collected explosive materials during free-flying. In this work we show for the first time a method for confirmation of landmines combining honeybee colonies containing a preconcentration material and subsequent monitoring of luminescence quenching.
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•Trace detection of explosive vapours is challenging in real-world environments.•By “preconcentrating” trace vapours onto solid substrates, higher amounts can be collected for detection.•Our approach combines polymer preconcentrators, honeybees for sampling, and luminescent thin films as the sensing mechanism.•The inexpensive, commercially-available fluoropolymer Aflas has shown good preconcentration abilities for 2,4-DNT.•Lab and field results indicate this method is a promising tool for detecting trace explosive vapours in contaminated land.
The parasitic mite Varroa destructor is a threat to beekeeping colonies. Among naturally derived acaricides, the monoterpenoid essential oil compound thymol is used in beekeeping for varroa mite ...control, but adverse impacts on honeybees has been already documented. Carvacrol, another monoterpenoid, also has a high acaricidal potential and could thus be promising for regular use in beekeeping, but information is scarce regarding the effects of prolonged systemic administration of carvacrol on honeybees. In this study, we evaluate and compared the sublethal effects of long term consumption of carvacrol and thymol on Carnolian honeybee workers (Apis mellifera carnica). Survival and feeding rate were determined preliminary to assess sublethal concentrations. The sublethal effects were analysed by the activity of the acetylcholinesterase (AChE), enzyme involved in the control of neurotransmission, and the activity of detoxifying enzyme glutathione S-transferase (GST) in heads and thoraces. We found that, thymol and carvacrol, caused mortality only at the highest concentrations tested, 1% and 5% respectively. As demonstrated by others, both substances could be effective against varroa at concentrations ten times lower than those causing significant honeybee mortality. However, we demonstrated sublethal effects at the 0.05% carvacrol and thymol exposure concentrations evidenced as increased activity of AChE and GST in the honeybee heads. In conclusion, prolonged treatment with thymol and carvacrol affects bee nervous system and induce detoxification processes possibly resulting in a limited use for acaricidal purposes. We postulate that under the same chronic exposure conditions carvacrol and thymol will have similar sublethal effects on honeybees.
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•Thymol and carvacrol increase mortality and feeding rate at high concentrations.•Chronic thymol and carvacrol oral treatment increase bee AChE and GST activity.•Carvacrol and thymol probably have similar sublethal effects on honey bees.
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•Varroosis has become a global problem for bee-keepers, and agriculture.•Was analysed influence of biotic and abiotic factors on colony health.•The local environmental factors impact ...the fall of Varroa destructor.•Environmentally friendly beekeeping reduces the causes of colony collapse disorder.
Colony collapse disorder has become a global problem for beekeepers, and agriculture, which depends on bee pollination. Among other factors, the impact of the parasitic mite V. destructor, which causes varroosis, increases the risk of bee colony collapse. Global climatic changes can affect honey bee colony fate on multiple levels, including the spread of its antagonist, the ectoparasite mite V. destructor. In this work, we presumed that local meteorological conditions and the choice of appropriate beekeeping management significantly influence the number of Varroa mites falling off of honey bees. Therefore, we examined using statistical analyses the relation between biotic (number of V. destructor in A. mellifera colonies, bee quine line) and abiotic factors (maximum, minimum and average daily temperature, maximum, minimum and average daily relative humidity, hive location). Ambient air temperature proved to be a significant factor in this issue. When the daily maximum temperature ranging from 25.1 to 31.7 °C and minimum daily temperature above 5.5 °C, there was an increase in the fall of V. destructor. The highest fall of V. destructor for the whole study period was recorded when the daily air temperature was increased between 13.9 and 28.7 °C and the humidity was decreased between 47.2 and 22.7 % in the hives located in the open space. This study shows that mite falls are also influenced by the hives' location and the beeline's hygienic characteristics. Therefore, beekeepers should consider these factors when planning management strategies.
Humanitarian demining is a worldwide effort and the range of climates and environments prevent any one detection method being suitable for all sites, so more tools are required for safe and efficient ...explosives sensing. Landmines emit a chemical flux over time, and honeybees can collect the trace residues of explosives (as particles or as vapour) on their body hairs. This capability was exploited using a passive method allowing the honeybees to freely forage in a mined area, where trace explosives present in the environment stuck to the honeybee body, which were subsequently transferred onto an adsorbent material for analysis by a fluorescent polymer sensor. Potential false positive sources were investigated, namely common bee pheromones, the anti-varroa pesticide Amitraz, and the environment around a clean apiary, and no significant response was found to any from the sensor. The mined site gave a substantial response in the optical sensor films, with quenching efficiencies of up to 38%. A model was adapted to estimate the mass of explosives returned to the colony, which may be useful for estimating the number of mines in a given area.
•Collection and detection of trace explosives is challenging in real-world environments.•Honeybees are used to passively collect explosives on body hair via free-flying.•Returning to the colony, the bees deposit explosives onto a sorbing preconcentrator for analysis by optical sensor.•Several potential distractant chemicals are tested and found not to give false positives.•A model has been developed to estimate the amount of explosive returned to the colony by the foraging bees.
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