Biology subjects

Sandoz, J.-C.

Publications and source records attributed to Sandoz, J.-C..

8 recordsLinked to original sources

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

Ancestral complexity and constrained diversification of the ant olfactory system

Ants are a monophyletic but diverse group of social insects whose heightened olfactory ability has been crucial to their evolutionary success. Their complex olfactory system is believed to have evolved due to the expansion of a specialized olfactory subsystem and the associated clade of olfactory receptors. Specifically, ants exhibit specialized antennal hairs known as basiconic sensilla, whose neurons project to a distinctive cluster of numerous, small glomeruli in their antennal lobes. This adaptation is believed to be linked to their social lifestyle, enabling the detection of recognition cues like cuticular hydrocarbons (CHCs), which are essential for nestmate recognition and maintaining colony cohesion. However, our understanding of the ant olfactory system remains incomplete, lacking evolutionary context and phylogenetic breadth, which leaves the complexity in their most recent common ancestor uncertain. We thus conducted a comparative study of neuroanatomical traits across the phylogeny of the Formicidae. Our findings reveal a common blueprint for the ant olfactory pathway, alongside lineage-specific adaptations. This highlights a dynamic evolution, particularly for the CHC-related subsystem. Ancestral trait reconstructions indicate that olfactory sophistication predates the most recent common ancestor of ants. Additionally, we found that the chemical complexity of species-specific recognition cues is associated with neuronal investment within the olfactory system. Lastly, behavioral experiments on anatomically divergent ant species show that, despite variation in neuroanatomical traits, ants consistently discriminate nestmates from non-nestmates. This suggests that the evolution of ants olfactory system integrates sensory adaptations to diverse chemical environments, facilitating communication, a key to social behaviors.

evolutionary biology↗

bioRxiv2023

Nutrient learning, perception and generalization differ among wild pollinator species

Learning is the process through which skills, knowledge, behaviors are acquired and developed. Through life experiences, pollinator insects, learn to associate odor or visual stimuli from flowers with a rewarding food as pollen or nectar. This capability allows them to obtain resources efficiently and provides a valuable pollination service. Here, we compared the learning capability among different wild pollinator insects by mean of experiments based on the recent Free-Moving Proboscis Extension Response (FMPER) technique. Specifically, we evaluated the process of perception, learning and generalization between pollen enriched with different concentrations of fatty acid (which play a critical role in the survival, development and reproduction of many animals). We compared the associative learning in two castes of bumble bees (queens and workers of Bombus terrestris), honey bees (Apis mellifera), solitary bees (Ruizanthedella mutabilis) and non-bee pollinator species (the hoverfly Eristalis tenax). Our results reveal that learning performances differed among bumble bee social castes, with queens acquiring learning odorants more effectively than workers. Likewise, learning performances differed among the four species of insect pollinators. Honey bees acquired odor-sucrose association more rapidly than the other species. Likewise, bumble bees learned better than the solitary bee species and the hoverfly. The pattern of generalization among odorant stimuli as also different among the studied species, with honey bees showing stronger generalization and hoverflies showing more specific response patterns. Studying the learning behavior in insect pollinators provides valuable information for the conservation of these species and services they provide, through adapted pollinator-friendly schemes matching their behavioral performances.

ecology↗

bioRxiv2022

Ants act as olfactory bio-detectors of tumour in patient-derived xenograft mice

Early detection of cancer is critical in medical sciences, as the sooner a cancer is diagnosed, the higher the chances of recovery. Tumour cells are characterized by specific volatile organic compounds (VOCs) that can be used as cancer biomarkers. Through olfactory associative learning, animals can be trained to detect these VOCs. Insects, such as ants, have a refined sense of smell and can be easily and rapidly trained with olfactory conditioning. Using urine from patient-derived xenograft mice as stimulus, we demonstrate that individual ants can learn to discriminate the odour of healthy mice from that of tumour bearing mice, and do so after only three conditioning trials. Chemical analyses confirmed that the presence of the tumour changed the urine odour, supporting the behavioural results. Our study demonstrates that ants reliably detect tumour cues in mice urine and have the potential to act as efficient and inexpensive cancer bio detectors.

animal behavior and cognition↗

bioRxiv2022

Multisite imaging of neural activity using a genetically encoded calcium sensor in the honey bee Apis mellifera

Understanding of the neural bases for complex behaviors in Hymenoptera insect species has been limited by a lack of tools that allow measuring neuronal activity simultaneously in different brain regions. Here, we developed the first pan-neuronal genetic driver in a Hymenopteran model organism, the honey bee, and expressed the calcium indicator GCaMP6f under the control of the honey bee synapsin promoter. We show that GCaMP6f is widely expressed in the honey bee brain, allowing to record neural activity from multiple brain regions. To assess the power of this tool, we focused on the olfactory system, recording simultaneous responses from the antennal lobe, and from the more poorly investigated lateral horn and mushroom body calyces. Neural responses to 16 distinct odorants demonstrate that odorant quality (chemical structure) and quantity are faithfully encoded in the honey bee antennal lobe. In contrast, odor coding in the lateral horn departs from this simple physico-chemical coding, supporting the role of this structure in coding the biological value of odorants. We further demonstrate robust neural responses to several bee pheromone odorants, key drivers of social behavior, in the lateral horn. Combined, these brain recordings represent the first use of a neurogenetic tool for recording large-scale neural activity in a eusocial insect, and will be of utility in assessing the neural underpinnings of olfactory and other sensory modalities and of social behaviors and cognitive abilities.

neuroscience↗

bioRxiv2021

Coevolution of the olfactory organ and its receptor repertoire in ray-finned fishes

Ray-finned fishes (Actinopterygii) perceive their environment through a range of sensory modalities, including olfaction 1,2. Anatomical diversity of the olfactory organ suggests that olfaction is differentially important among species 1,3,4. To explore this topic, we studied the evolutionary dynamics of the four main gene families (OR, TAAR, ORA/VR1 and OlfC/VR2) 5 coding for olfactory receptors in 185 species of ray-finned fishes. The large variation in the number of functional genes, between 28 in the Ocean Sunfish Mola mola and 1317 in the Reedfish Erpetoichthys calabaricus, is the result of parallel expansions and contractions of the four main gene families. Several ancient and independent simplifications of the olfactory organ are associated with massive gene losses. In contrast, polypteriforms, which have a unique and complex olfactory organ, have almost twice as many olfactory receptor genes as any other ray-finned fish. These observations suggest a functional link between morphology of the olfactory organ and richness of the olfactory receptor repertoire. Further, our results demonstrate that the genomic underpinning of olfaction in ray-finned fishes is heterogeneous and presents a dynamic pattern of evolutionary expansions, simplifications and reacquisitions.

evolutionary biology↗

bioRxiv2021

Evolutionary dynamics of the OR gene repertoire in teleost fishes: evidence of an association with changes in olfactory epithelium shape

Teleost fishes perceive their environment through a range of sensory modalities, among which olfaction often plays an important role. Richness of the olfactory repertoire depends on the diversity of receptors coded by homologous genes classified into four families: OR, TAAR, VR1 and VR2. Herein, we focus on the OR gene repertoire. While independent large contractions of the OR gene repertoire associated with ecological transitions have been found in mammals, little is known about the diversity of the OR gene repertoire and its evolution within teleost fishes, a group that includes more than 34,000 living species. We analyzed genomes of 163 species representing diversity in this large group. We found a large range of variation in the number of functional OR genes, from 15 in Syngnathus typhle and Mola mola, to 429 in Mastacembelus armatus. The number of OR genes was higher in species with an extensively folded olfactory epithelium, that is, for example, when a multi-lamellar rosette was present in the olfactory organ. Moreover, the number of lamellae was correlated with the richness of the OR gene repertoire. While a slow and balanced birth-and-death process generally drives evolution of the OR gene repertoire, we inferred several episodes of high rates of gene loss, sometimes followed by large gains in the number of OR genes. These gains coincide with morphological changes of the olfactory organ and suggest a strong functional association between changes in the morphology and the evolution of the OR gene repertoire.

evolutionary biology↗

bioRxiv2021

Olfactory coding in the bumble bee antennal lobe

Sociality is classified as one of the major transitions in evolution, with the largest number of eusocial species found in the insect order Hymenoptera, including the Apini (honey bees) and the Bombini (bumble bees). Bumble bees and honey bees not only differ in their social organization and foraging strategies, but comparative analyses of their genomes demonstrated that bumble bees have a slightly less diverse family of olfactory receptors than honeybees, suggesting that their olfactory abilities have adapted to different social and/or ecological conditions. However, unfortunately, no precise comparison of olfactory coding has been performed so far between honey bees and bumble bees, and little is known about the rules underlying olfactory coding in the bumble bee brain. In this study, we used in vivo calcium imaging to study olfactory coding of a panel of floral odorants in the antennal lobe (AL) of the bumble bee Bombus terrestris. Our results show that odorants evoke consistent neuronal activity in the bumble bee antennal lobe. Each odorant evokes a different glomerular activity pattern revealing this molecules chemical structure, i.e. its carbon chain length and functional group. Response intensity as well as odor-similarity relationships were highly correlated to those measured in honey bees. This study thus suggests that bumble bees, like honey bees, are equipped to respond to odorants according to their chemical features.

neuroscience↗