Effects of Some Insecticides on the Viability and the ATP Synthesis of Honeybee Drone’s Spermatozoid in vitro Exposed

Honeybee (Apis mellifera) reproduction is polyandrous: the queen obtains millions of spermatozoid by mating with several drones outside the colony. Fertility problems of honeybee queens are reported where failure of the production and quality of sperm drones are suspected. Several factors can affect sperm quality drones include pesticides. The aim of this study is to determinate the in vitro effect of fipronil, ethiprole, imidacloprid, thiamethoxam, cypermethrin, and coumaphos at different concentrations from 0.1 to 100 µM on the viability and the energetic state, through ATP content, of spermatozoids of honeybee drones. Exposure during 24 h showed that all the active ingredients used in this test increase the ATP levels. Four of them i.e. fipronil, ethiprole, imidacloprid, and thiamethoxam reduced significantly the viability of spermatozoids. Hence, pesticides could affect the drone’s spermatozoids which may have negative impact on semen quality and further queen fecundity

Behavioral and metabolic effects of sublethal doses of two insecticides, chlorpyrifos and methomyl, in the Egyptian cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae)

International audienceInsecticides have long been used as the main method in limiting agricultural pests, but their widespread use has resulted in environmental pollution, development of resistances, and biodiversity reduction. The effects of insecticides at low residual doses on both the targeted crop pest species and beneficial insects have become a major concern. In particular, these low doses can induce unexpected positive (hormetic) effects on pest insects, such as surges in population growth exceeding what would have been observed without pesticide application. Methomyl and chlorpyrifos are two insecticides commonly used to control the population levels of the cotton leafworm Spodoptera littoralis, a major pest moth. The aim of the present study was to examine the effects of sublethal doses of these two pesticides, known to present a residual activity and persistence in the environment, on the moth physiology. Using a metabolomic approach, we showed that sublethal doses of methomyl and chlorpyrifos have a systemic effect on the treated insects. We also demonstrated a behavioral disruption of S. littoralis larvae exposed to sublethal doses of methomyl, whereas no effects were observed for the same doses of chlorpyrifos. Interestingly, we highlighted that sublethal doses of both pesticides did not induce a change in acetylcholinesterase activity in head of exposed larva

Gut Pathology and Responses to the Microsporidium Nosema ceranae in the Honey Bee Apis mellifera

The microsporidium Nosema ceranae is a newly prevalent parasite of the European honey bee (Apis mellifera). Although this parasite is presently spreading across the world into its novel host, the mechanisms by it which affects the bees and how bees respond are not well understood. We therefore performed an extensive characterization of the parasite effects at the molecular level by using genetic and biochemical tools. The transcriptome modifications at the midgut level were characterized seven days post-infection with tiling microarrays. Then we tested the bee midgut response to infection by measuring activity of antioxidant and detoxification enzymes (superoxide dismutases, glutathione peroxidases, glutathione reductase, and glutathione-S-transferase). At the gene-expression level, the bee midgut responded to N. ceranae infection by an increase in oxidative stress concurrent with the generation of antioxidant enzymes, defense and protective response specifically observed in the gut of mammals and insects. However, at the enzymatic level, the protective response was not confirmed, with only glutathione-S-transferase exhibiting a higher activity in infected bees. The oxidative stress was associated with a higher transcription of sugar transporter in the gut. Finally, a dramatic effect of the microsporidia infection was the inhibition of genes involved in the homeostasis and renewal of intestinal tissues (Wnt signaling pathway), a phenomenon that was confirmed at the histological level. This tissue degeneration and prevention of gut epithelium renewal may explain early bee death. In conclusion, our integrated approach not only gives new insights into the pathological effects of N. ceranae and the bee gut response, but also demonstrate that the honey bee gut is an interesting model system for studying host defense responses

Exposure to Sublethal Doses of Fipronil and Thiacloprid Highly Increases Mortality of Honeybees Previously Infected by Nosema ceranae

International audienceBACKGROUND: The honeybee, Apis mellifera, is undergoing a worldwide decline whose origin is still in debate. Studies performed for twenty years suggest that this decline may involve both infectious diseases and exposure to pesticides. Joint action of pathogens and chemicals are known to threaten several organisms but the combined effects of these stressors were poorly investigated in honeybees. Our study was designed to explore the effect of Nosema ceranae infection on honeybee sensitivity to sublethal doses of the insecticides fipronil and thiacloprid. METHODOLOGY/FINDING: Five days after their emergence, honeybees were divided in 6 experimental groups: (i) uninfected controls, (ii) infected with N. ceranae, (iii) uninfected and exposed to fipronil, (iv) uninfected and exposed to thiacloprid, (v) infected with N. ceranae and exposed 10 days post-infection (p.i.) to fipronil, and (vi) infected with N. ceranae and exposed 10 days p.i. to thiacloprid. Honeybee mortality and insecticide consumption were analyzed daily and the intestinal spore content was evaluated 20 days after infection. A significant increase in honeybee mortality was observed when N. ceranae-infected honeybees were exposed to sublethal doses of insecticides. Surprisingly, exposures to fipronil and thiacloprid had opposite effects on microsporidian spore production. Analysis of the honeybee detoxification system 10 days p.i. showed that N. ceranae infection induced an increase in glutathione-S-transferase activity in midgut and fat body but not in 7-ethoxycoumarin-O-deethylase activity. CONCLUSIONS/SIGNIFICANCE: After exposure to sublethal doses of fipronil or thiacloprid a higher mortality was observed in N. ceranae-infected honeybees than in uninfected ones. The synergistic effect of N. ceranae and insecticide on honeybee mortality, however, did not appear strongly linked to a decrease of the insect detoxification system. These data support the hypothesis that the combination of the increasing prevalence of N. ceranae with high pesticide content in beehives may contribute to colony depopulation

L'acetylcholinesterase d'un invertebre, Apis mellifera : proprietes physicochimiques, polymorphisme et interactions membranaires

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

L'acétylcholinestérase d'un invertébré : Apis mellifera. propriétés physico-chimiques, polymorphisme et interactions membranaires

* INRA, URD, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9 Diffusion du document : INRA, URD, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9 Diplôme : Dr. d'Universit

Les effets sublétaux des pesticides chez l'abeille (Apis mellifera)

National audiencePlant protection products, also called pesticides, include numerous chemical families. They are distributed in classes of molecules having different biological actions among which fungicides, herbicides, insecticides and acaricides are the most used. Pesticides can present a lethal action that is relatively easy to characterise. They are also able to induce, at different exposure levels, adverse or non adverse sublethal effects. The adverse sublethal effects may be of physiological, neural, behavioural or biochemical nature but, in all cases, they put at risk the fitness or the survival of individuals and/or populations. Generally, a pesticide does not elicit a unique action but induces numerous effects that are not always characterised easily. The final impacts of adverse sublethal effects of pesticides in bees leads to weakening of colonies, a decrease of hive product gathering and to an alteration of the entomophilic pollination.Les produits phytopharmaceutiques, encore appelés pesticides, regroupent de nombreuses familles chimiques. Ils sont distribués en classes de molécules ayant des actions biologiques distinctes dont les fongicides, les herbicides, les insecticides et les acaricides sont parmi les plus utilisées. Les pesticides peuvent présenter une action létale qu’il est assez facile de caractériser. Ils sont aussi capables d’induire, à différents niveaux d’exposition, des effets sublétaux délétères ou non. Les effets sublétaux délétères peuvent être de nature physiologique, neurale, comportementale ou biochimique mais, dans tous les cas, compromettent la vitalité et/ou la survie des individus ou des populations. Généralement, l’action d’un pesticide ne se résume pas à un effet unique mais conduit à l’induction de nombreux effets qu’il n’est pas toujours aisé de caractériser. L’action finale des effets sublétaux délétères des pesticides chez l’abeille aboutit à un affaiblissement plus ou moins drastique des colonies, à une diminution des récoltes de produits de la ruche et à une altération de la pollinisation entomophile

Modes d'action des néonicotinoïdes (étude comparée des mécanismes d'absorption et de métabolisation chez un invertébré, l'abeille domestique (Apis mellifera L.), et chez un vertébré, l'homme)

Le rôle de l'absorption et de la métabolisation dans la toxicité différentielle de l'acétamipride (AAP) et de l'imidaclopride (IMI) est évalué chez l'abeille et chez l'Homme. Chez l'abeille, l'absorption et la distribution de l'AAP sont très rapides et similaires à celles de l'IMI. Les métabolites de l'AAP tendent à persister dans l'organisme et diffèrent de ceux de l'IMI, expliquant la toxicité différente des deux molécules. L'absorption des deux molécules, étudiée au moyen de la lignée cellulaire humaine Caco-2, permet de prédire une absorption intestinale importante. Les mécanismes de transports passifs et actifs impliqués diffèrent pour les deux molécules. Chez l'homme, la métabolisation de l'AAP par des hépatocytes et par des microsomes hépatiques conduit à un seul métabolite en impliquant majoritairement le cytochrome P450 CYP2C9 dont l'hétérogénéité au sein de la population induirait un risque sanitaire différent pour les individus si le seul métabolite de l'AAP était toxiqueAIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Glutamatergic neuromuscular transmission properties studied in single skeletal muscle fibers from adult honeybee

International audienceAdult honeybee glutamatergic neuromuscular transmission properties have been explored at the macroscopic and single-channel level with the patch-clamp technique on single muscle fibers enzymatically isolated from metathoracic leg tibias. In the whole-cell configuration, dose-responses curves obtained with a computer-operated and pressure-driven fast perfusion system indicate that the two kinetically distinct components activated by L-glutamate have different affinity for the physiological agonist. Moreover, a component of the current, sustained throughout the perfusion with L-glutamate reverses close to 0 mV, while a fast inactivating component of the current reverses at more negative potentials. The glutamate channels agonists and antagonists classically known to affect neuromuscular transmission in skeletal muscle from other invertebrates (quisqualic acid, ibotenic acid and picrotoxin) were used to characterize the glutamatergic transmission pharmacology in honeybee. Single channel currents were also recorded from cell-attached and outside-out patches. The data obtained suggest that both qGluR and GluCl ion channels are present in the membrane of adult honeybee tibia muscle fibers. The single muscle fiber preparation described here provides a convenient way to study adult neuromuscular transmission in invertebrates, as well as its perturbation by pesticides targeting junctional or extrajunctional ionotropic glutamate receptors