In Vitro Effects of Pesticides on European Foulbrood in Honeybee Larvae

Neonicotinoid and fungicide exposure has been linked to immunosuppression and increased susceptibility to disease in honeybees (Apis mellifera). European foulbrood, caused by the bacterium Melissococcus plutonius, is a disease of honeybee larvae which causes economic hardship for commercial beekeepers, in particular those whose colonies pollinate blueberries. We report for the first time in Canada, an atypical variant of M. plutonius isolated from a blueberry-pollinating colony. With this isolate, we used an in vitro larval infection system to study the effects of pesticide exposure on the development of European foulbrood disease. Pesticide doses tested were excessive (thiamethoxam and pyrimethanil) or maximal field-relevant (propiconazole and boscalid). We found that chronic exposure to the combination of thiamethoxam and propiconazole significantly decreased the survival of larvae infected with M. plutonius, while larvae chronically exposed to thiamethoxam and/or boscalid or pyrimethanil did not experience significant increases in mortality from M. plutonius infection in vitro. Based on these results, individual, calculated field-realistic residues of thiamethoxam and/or boscalid or pyrimethanil are unlikely to increase mortality from European foulbrood disease in honeybee worker brood, while the effects of field-relevant exposure to thiamethoxam and propiconazole on larval mortality from European foulbrood warrant further study.

Genome Architecture Facilitates Phenotypic Plasticity in the Honeybee (Apis mellifera)

Phenotypic plasticity, the ability of an organism to alter its phenotype in response to an environmental cue, facilitates rapid adaptation to changing environments. Plastic changes in morphology and behavior are underpinned by widespread gene expression changes. However, it is unknown if, or how, genomes are structured to ensure these robust responses. Here, we use repression of honeybee worker ovaries as a model of plasticity. We show that the honeybee genome is structured with respect to plasticity; genes that respond to an environmental trigger are colocated in the honeybee genome in a series of gene clusters, many of which have been assembled in the last 80 My during the evolution of the Apidae. These clusters are marked by histone modifications that prefigure the gene expression changes that occur as the ovary activates, suggesting that these genomic regions are poised to respond plastically. That the linear sequence of the honeybee genome is organized to coordinate widespread gene expression changes in response to environmental influences and that the chromatin organization in these regions is prefigured to respond to these influences is perhaps unexpected and has implications for other examples of plasticity in physiology, evolution, and human disease.

Volatiles from Different Instars of Honeybee Worker Larvae and Their Food

(E)-β-Ocimene was the only volatile chemical found to be emitted by whole, live worker larvae of Apis mellifera L. when sampling in the vapor phase. In addition to (E)-β-ocimene, there is evidence for the existence of other volatiles, but the changes in their composition and contents remain unknown during larval development, as are their differences from larvae to larval food. We investigated volatile components of worker larvae and larval food using solid phase dynamic extraction (SPDE) coupled with gas chromatography-mass spectrometry (GC-MS). Nine compounds were identified with certainty and six tentatively, including terpenoids, aldehydes, hydrocarbons, an ester and a ketone. The contents of volatiles in the second-instar worker larvae differ greatly from those in larvae of other stages. This is mainly attributable to terpenoids, which resulted in the second-instar worker larvae having significantly higher amounts of overall volatiles. Larval food contained significantly higher amounts of aldehydes and hydrocarbons than the corresponding larvae from the fourth to fifth-instar. We discovered volatiles in worker larvae and their food that were never reported before; we also determined the content changes of these volatiles during larval development.

GC-MS Investigation of Volatiles from Honeybee Worker Larvae and Larval Food at Different Instars

(E)-β-ocimene was the only found volatile chemical emitted by whole, live worker larvae of Apis mellifera L. by sampling in the vapor phase. While in addition to (E)-β-ocimene, there is evidence for the existence of other volatiles; but the changes of their composition and contents remain unknown during larval development, as are their differences from larvae to larval food. This is the main purpose of the study. We investigated volatile components of worker larvae and larval food using solid phase dynamic extraction (SPDE) coupled with gas chromatography-mass spectrometry (GC-MS). Nine compounds were identified with certainty and six tentatively, consisting of terpenoids, aldehydes, hydrocarbons, ester and ketone. The contents of volatiles of the second-instar worker larvae differ greatly from larvae of other stages mainly attributable to terpenoids, which made the second-instar worker larvae had significantly higher amounts of overall volatiles. Larval food contained significantly higher amounts of aldehydes and hydrocarbons than the corresponding larvae from the fourth to fifth-instar. We discovered volatiles in worker larvae and their food which were never reported before; we also mastered the change of these volatiles’ contents during larval development.

Effects of Some Insecticides on the Midgut of the Foragers Honeybee Worker Apis mellifera jemenatica

This study aims to evaluate the toxic effects of insecticides on the foragers honey bee workers, Apis mellifera jemenatica. It tracks the effects of the insecticides, Deltamethrin, Malathion and Abamectin through the feeding by mouth, on the midgut epithelial layer, in order to show the histological changes. Histological study on samples of the foragers honey bee workers, after exposure to insecticides for 24 hours, was chosen as the average -concentration of the insecticide concentrations, which were used for each as follows: Deltamethrin 2.50 ppm, Malathion 3.125 ppm and Abamectin 0.1 ppm, in addition to the control group. Studying the effect of each insecticide individually and then comparing the reaction and impact of these insecticides on the tissue of midgut has showed that the insecticide Malathion was more harmful to epithelial tissue midgut in honey bees cells than Abamectin, while Deltamethrin had the least effect. Therefore, the life of the foragers honeybee worker depends upon the health and safety of the entire members of the beehive, so it is necessary to take into account, when using the application of insecticides, the continuity of life of the entire society adoption of individuals beehive on worker bees layer depends on their life on this layer of the bee community.