Biology subjects

Cochard, P.

Publications and source records attributed to Cochard, P..

6 recordsLinked to original sources

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↗

bioRxiv2025

Comparing the Seasonal Diets of Buff-tailed Bumblebees and Honey Bees in a Forest Landscape: A Metabarcoding Approach

The declining diversity of pollinating insects is a major threat to ecosystem conservation, pollination services, and global food security. Honeybees (Apis mellifera L.) dominate managed pollination, but their dominance can affect other pollinators. Competition for resources can lead to decreased foraging success and survival rates for wild bees, especially bumblebees. This study explores the dietary composition of honeybees and buff-tailed bumblebees (Bombus terrestris L.) using metabarcoding techniques with three primers (ITS2, TrnLgh, and TrnLch) in Avensan, France. Primers detected different species pools, indicating a high diversity of plants visited by both species - including some false positives results inherent to metabarcoding methods. The "primer" effect was more important than the "pollinator" effect in segregating plants found. The Schoener index revealed a slight diet overlap in plant species used by honeybees and bumblebees, depending on the primer. Correspondence analyses showed a high segregation between species associated with honeybees or with bumblebees, regardless of the primer. The metabarcoding technique was found to be accurate in separating pollinator food niches, despite some biases of this technique: this result is not comparable with previous literature studying the diets of these two species, as traditional [fi]eld studies are needed to complement it and overcome these biases. To conclude, this study provides a fast and inexpensive approach to study pollinators floral resources sharing in the same geographical area and time scale, and provide insights to improve metabarcoding effectiveness in order to better describe diet niches.

ecology↗

bioRxiv2020

Sulf2a controls Shh-dependent neural fate specification in the developing spinal cord

Sulf2a belongs to the Sulf family of extracellular sulfatases which selectively remove 6-O-sulfate groups from heparan sulfates, a critical regulation level for their role in modulating the activity of signalling molecules. Data presented here define Sulf2a as a novel player in the control of Sonic Hedgehog (Shh)-mediated cell type specification during spinal cord development. We show that Sulf2a depletion in zebrafish results in overproduction of V3 interneurons at the expense of motor neurons and also impedes generation of oligodendrocyte precursor cells (OPCs), three cell types that depend on Shh for their generation. We provide evidence that Sulf2a, expressed in a spatially restricted progenitor domain, acts by maintaining the correct patterning and specification of ventral progenitors. More specifically, Sulf2a prevents Olig2 progenitors to activate high-threshold Shh response and, thereby, to adopt a V3 interneuron fate, thus ensuring proper production of motor neurons and OPCs. We propose a model in which Sulf2a reduces Shh signalling levels in responding cells by decreasing their sensitivity to the morphogen factor. More generally, our work, revealing that, in contrast to its paralog Sulf1, Sulf2a regulates neural fate specification in Shh target cells, provides direct evidence of non-redundant functions of Sulfs in the developing spinal cord.

developmental biology↗

bioRxiv2018

Identification of a Sulf2-dependant astrocyte subtype that stands out through the expression of Olig2 in the ventral spinal cord

During spinal cord development, both spatial and temporal mechanisms operate to generate glial cell diversity. Here, we addressed the role of the Heparan Sulfate-editing enzyme Sulf2 in the control of gliogenesis in the mouse developing spinal cord and found an unanticipated function for this enzyme. Sulf2 is expressed in ventral spinal progenitors at initiation of gliogenesis, including in Olig2-expressing cells of the pMN domain known to generate most spinal cord oligodendrocyte precursor cells (OPCs). We found that Sulf2 is dispensable for OPC development but required for proper generation of an as-yet-unidentified astrocyte precursor cell (AP) subtype. These cells, like OPCs, express Olig2 while populating the spinal parenchyma at embryonic stages but also retain Olig2 expression as they differentiate into mature astrocytes. We therefore identify a spinal Olig2-expressing AP subtype that segregates early under the influence of the extracellular enzyme Sulf2.

developmental biology↗

bioRxiv2017

FGFs are orchestra conductors of Shh-dependent oligodendroglial fate specification in the ventral spinal cord

Most oligodendrocytes of the spinal cord originate from ventral progenitor cells of the pMN domain, characterized by expression of the transcription factor Olig2. A minority of oligodendrocytes is also recognized to emerge from dorsal progenitors during fetal development. The prevailing view is that generation of ventral oligodendrocytes depends on Sonic hedgehog (Shh) while dorsal oligodendrocytes develop under the influence of Fibroblast Growth Factors (FGFs). Using the well-established model of the chicken embryo, we evidence that ventral spinal progenitor cells activate FGF signaling at the onset of oligodendrocyte precursor cell (OPC) generation, as do they dorsal counterpart. Inhibition of FGF receptors at that time appears sufficient to prevent generation of ventral OPCs, highlighting that, in addition to Shh, FGF signaling is required also for generation of ventral OPCs. We further reveal an unsuspected interplay between Shh and FGF signaling by showing that FGFs serve dual essential functions in ventral OPC specification. FGFs are responsible for timely induction of a secondary Shh signaling center, the lateral floor plate, a crucial step to create the burst of Shh required for OPC specification. At the same time, FGFs prevent down-regulation of Olig2 in pMN progenitor cells as these cells receive higher threshold of the Shh signal. Finally, we bring arguments favoring a key role of newly differentiated neurons acting as providers of the FGF signal required to trigger OPC generation in the ventral spinal cord.

developmental biology↗