Biology subjects

Charistos, L.

Publications and source records attributed to Charistos, L..

4 recordsLinked to original sources

bioRxiv2026

Conserved task-specific profiles outweigh seasonal shifts in cuticular hydrocarbons of European honey bee subspecies

Cuticular hydrocarbons (CHCs) are essential for insect waterproofing, yet how they change seasonally in social insects remains poorly understood. Due to its distinct seasonal worker phenotypes (summer and winter bees) and diverse subspecies, the western honey bee (Apis mellifera) is an ideal model to study seasonal CHC plasticity across populations with distinct local adaptations. We performed a common garden experiment to investigate the seasonal plasticity in CHC profiles across five European subspecies (A. m. carnica, A. m. iberiensis, A. m. ligustica, A. m. macedonica, A. m. ruttneri). We compared the CHC composition of workers performing tasks inside ("in-hive") or outside ("out-hive") the colony during summer and winter. Notably, out-hive workers consistently exhibited more waterproofing CHC profiles compared to in-hive workers, regardless of season or subspecies. The persistence of this stereotypical task-related differentiation in long-lived winter bees, which largely lack an age-based division of labor, indicates a robust, age-independent regulatory mechanism linked to the environment faced by the workers rather than a simple response to seasonal desiccation pressure. Moreover, we demonstrate CHC seasonal plasticity for the first time in honey bees. However, these seasonal shifts in hydrocarbon classes and chain length were not uniform; they varied across subspecies and critically depended on the task the workers performed.

ecology↗

bioRxiv2025

Reducing Honey Bee Winter Mortality with Molybdenum Supplementation: Field Evidence Across Europe

Nutrition is key to improve honey bees resilience to environmental stress factors that threaten their health. Yet, little is known about the micronutritional needs of colonies, in particular about molybdenum, an essential trace element in biology. This study focuses on a coordination complex based on molybdenum Mo(+V) which was assessed for compatibility with standard beekeeping practices. It was found to be non-toxic for bees, stable and easy to use. Importantly, it does not leave any residues in honey produced. This study investigated how supplementation with few milligrams of this complex can improve hive performance at early spring and reduce winter mortality. Over a two-year field campaign, 283 beehives spread over 6 apiaries located in Spain, Greece and France were involved: 142 beehives supplemented with the molybdenum-based compound and 141 beehives as a control group. Supplementation resulted in a significant reduction in winter colony losses, averaging a 44% decrease, ranging between 27% and 75% in the different apiaries. The risk of death was twice lower in the Na-Mo2O4-EDTA group compared to the control group (risk ratio: 0.51). The impact on bee populations and honey production was also evaluated. A significant increase in honey reserves within the brood area of 107% was observed in the Greek apiary, whereas no comparable effect was detected in Spain, suggesting that local environmental conditions or management practices may influence this parameter. This study highlights the importance of molybdenum in the management of honey bees as an efficient tool to reduce the winter mortality of the colonies. HighlightsO_LIMolybdenum-based feed supplementation reduced honey bee winter mortality by 44% in average and up to 75% C_LIO_LIThere are no adverse effects on honey bee health or honey and wax composition. C_LIO_LISupplement showed variable effects on honey reserves and no effects on bee population. C_LIO_LIALP levels increased transiently, while the TAC was unaffected.Supplementation with Molybdenum-based compound represents a promising strategy to enhance colony overwintering success C_LI

zoology↗

bioRxiv2025

Food supplementation with molybdenum complexes improves honey bee health

In this study, we evaluated the impact of supplementing honey bee feed with molybdenum-based compounds. Among a dozen of dinuclear Mo(V) complexes, we first selected the most stable and non-toxic complexes, which were tested as food supplements in an extensive eight-year campaign involving more than 700 beehives across various environmental conditions in Moldova, France, Greece and USA. This unprecedented field campaign revealed that a few milligrams of compounds Na-Mo2O4-EDTA or Li-Mo2O4-EDTA provided in spring or autumn, increased queen fecundity, hygienic behavior, and honey production, while infestation rates of worker bees and brood by the mite Varroa destructor, and mortality rates in winter were dramatically reduced. Hive monitoring showed that the Mo-containing syrup can be consumed over 1.5 months and is well assimilated by larvae and workers within the hive. In particular, Mo levels increased significantly in the head of the bees. X-ray fluorescence measurements demonstrated that Na-Mo2O4-EDTA increases Mo levels in brain, neurolemma and hypopharyngeal glands. The metabolism of Mo complexes was addressed using X-Ray photoelectron spectroscopy (XPS) on bee faeces, which revealed that the complexes are oxidized into Mo(VI) species and thus suggesting that Mo complexes may function as antioxidant agents in bees. These findings offer promising solutions for the beekeeping industry, which is struggling with weakening honey bee colonies. Significance StatementHoney bees play a crucial role as pollinators. Unfortunately, colony losses have increased significantly over the past decades through the action of multiple environmental stressors. Currently, solutions are sought to strengthen bees health and resilience. This study shows that feeding bees with small amounts of trace elements like molybdenum can improve honey bee condition and increase the production of hive products. Through an unprecedented series of field and lab tests it notably demonstrates that molybdenum complexes are i) non-toxic, ii) consumed by bees over several generations, iii) assimilated particularly in the brain and hypopharyngeal glands, iv) acting as antioxidant. These results open new avenues for using trace elements to improve pollinator health.

zoology↗

bioRxiv2024

Deciphering the variation in cuticular hydrocarbon profiles of five European honey bee subspecies

The Western honey bee (Apis mellifera) subspecies exhibit local adaptive traits that evolved in response to the different environments that characterize their native distribution ranges. An important trait is the cuticular hydrocarbon (CHC) profile, which helps preventing desiccation and mediating communication. We compared the CHC profiles of six European subspecies (A. m. mellifera, A. m. carnica, A. m. ligustica, A. m. macedonica, A. m. iberiensis, and A. m. ruttneri) and investigated potential factors shaping their composition. We did not find evidence of adaptation of the CHC profiles of the subspecies to the climatic conditions in their distribution range. Subspecies-specific differences in CHC composition might be explained by phylogenetic constraints or genetic drift. The CHC profiles of foragers were more subspecies-specific than those of nurse bees, while the latter showed more variation in their CHC profiles, likely due to the lower desiccation stress exerted by the controlled environment inside the hive. The strongest profile differences appeared between nurse bees and foragers among all subspecies, suggesting an adaptation to social task and a role in communication. Foragers also showed an increase in the relative amount of alkanes in their profiles compared to nurses, indicating adaptation to climatic conditions.

evolutionary biology↗