9 research outputs found
Sperm numbers in drone honeybees (Apis mellifera) depend on body size
No full textThe effect of drone honeybee's body size on semen production was evaluated. In the same colonies, drones were either reared in drone cells (large drones) or in worker cells (small drones). Wing lengths (size indicator) and sperm numbers of small and large drones were compared. Small drones (~13% reduced wing size) produce significantly fewer spermatozoa (7.5 0.5 million) than normally sized drones (11.9 1.0 million spermatozoa). There is a significant positive correlation between sperm number and wing size within the small drones and in both groups combined. In the large group alone no correlation was found. The rearing investment per spermatozoon is lower for small than for normally sized drones because small drones produce more spermatozoa in relation to their body weight. Since colonies usually produce large drones, the enhanced investment must be outweighed by a mating advantage of large drones
Testing reliability of a potential island mating apiary using DNA microsatellites
No full textInternational audienc
Testing reliability of a potential island mating apiary using DNA microsatellites
No full textTwenty-four virgin sister queens were kept for 21 days in mating nuclei on the drone-free island Baltrum to test the reliability of a potential mating area. On each of the neighbouring islands Nordemey and Langeoog (750 m and 2 km away) 12 sister queens were kept with drones. Workers from colonies with island-mated queens (Baltrum n = 11, Langeoog n = 7 and Nordemey n = 6) were genotyped with four DNA microsatellite loci (n = 996) to estimate queen mating frequency. No differences in queen mating frequency were observed between Langeoog and Nordemey. However, the level of polyandry on Baltrum was significantly lower than on the neighbouring islands, indicating that mating conditions were much more difficult. The standard genetic distance and differences in allele frequencies between the populations were determined to estimate putative origins of the drones. In this study, 43.7 % of the identified drone fathers did not descend from any of the queens on the adjacent islands. They were most likely from mainland colonies at least 5.4 km (3 km across open water) away, showing that the combination of distances over open water and over dry land is important in explaining the mating behaviour of honeybee queens. © Inra/DIB/AGIB/Elsevier, Pari
Infestation levels of Apis mellifera scutellata swarms by socially parasitic Cape honeybee workers (Apis mellifera capensis)
No full textInternational audienc
Infestation levels of Apis mellifera scutellata swarms by socially parasitic Cape honeybee workers (Apis mellifera capensis)
No full textA single clonal lineage of socially parasitic Cape honeybee workers, Apis mellifera capensis, has caused dramatic losses in managed populations of A. m. scutellata, raising concerns that wild populations might also be affected. We surveyed A. m. scutellata swarms at 27 localities in beekeeping areas (N = 87) and in nature reserves (N = 79). While eleven swarms were infested in beekeeping areas, we found no infestations in nature reserves. Eight swarms had no symptoms except workers with black tergites. However, DNA data revealed that these workers are not parasitic, showing that diagnoses based on tergite colour alone yield false positive results. Nevertheless, it is practical because we had no false negative diagnoses either. Nature reserves may be important refuges to protect wild A. m. scutellata populations against imported honeybees
Conclusions of the Worldwide Integrated Assessment on the risks of neonicotinoids and fipronil to biodiversity and ecosystem functioning
No full textThe side effects of the current global use of pesticides on wildlife, particularly at higher levels of biological organization: populations, communities and ecosystems, are poorly understood (Köhler and Triebskorn 2013). Here, we focus on one of the problematic groups of agrochemicals, the systemic insecticides fipronil and those of the neonicotinoid family. The increasing global reliance on the partly prophylactic use of these persistent and potent neurotoxic systemic insecticides has raised concerns about their impacts on biodiversity, ecosystem functioning and ecosystem services provided by a wide range of affected species and environments. The present scale of use, combined with the properties of these compounds, has resulted in widespread contamination of agricultural soils, freshwater resources, wetlands, non-target vegetation and estuarine and coastal marine systems, which means that many organisms inhabiting these habitats are being repeatedly and chronically expose ..
Systemic insecticides (neonicotinoids and fipronil): trends, uses, mode of action and metabolites
No full textSince their discovery in the late 1980s, neonicotinoid pesticides have become the most widely used class of insecticides worldwide, with large-scale applications ranging from plant protection (crops, vegetables, fruits), veterinary products, and biocides to invertebrate pest control in fish farming. In this review, we address the phenyl-pyrazole fipronil together with neonicotinoids because of similarities in their toxicity, physicochemical profiles, and presence in the environment. Neonicotinoids and fipronil currently account for approximately one third of the world insecticide market; the annual world production of the archetype neonicotinoid, imidacloprid, was estimated to be ca. 20,000 tonnes active substance in 2010. There were several reasons for the initial success of neonicotinoids and fipronil: (1) there was no known pesticide resistance in target pests, mainly because of their recent development, (2) their physicochemical properties included many advantages over previous generations of insecticides (i.e., organophosphates, carbamates, pyrethroids, etc.), and (3) they shared an assumed reduced operator and consumer risk. Due to their systemic nature, they are taken up by the roots or leaves and translocated to all parts of the plant, which, in turn, makes them effectively toxic to herbivorous insects. The toxicity persists for a variable period of time—depending on the plant, its growth stage, and the amount of pesticide applied. A wide variety of applications are available, including the most common prophylactic non-Good Agricultural Practices (GAP) application by seed coating. As a result of their extensive use and physicochemical properties, these substances can be found in all environmental compartments including soil, water, and air. Neonicotinoids and fipronil operate by disrupting neural transmission in the central nervous system of invertebrates. Neonicotinoids mimic the action of neurotransmitters, while fipronil inhibits neuronal receptors. In doing so, they continuously stimulate neurons leading ultimately to death of target invertebrates. Like virtually all insecticides, they can also have lethal and sublethal impacts on non-target organisms, including insect predators and vertebrates. Furthermore, a range of synergistic effects with other stressors have been documented. Here, we review extensively their metabolic pathways, showing how they form both compound-specific and common metabolites which can themselves be toxic. These may result in prolonged toxicity. Considering their wide commercial expansion, mode of action, the systemic properties in plants, persistence and environmental fate, coupled with limited information about the toxicity profiles of these compounds and their metabolites, neonicotinoids and fipronil may entail significant risks to the environment. A global evaluation of the potential collateral effects of their use is therefore timely. The present paper and subsequent chapters in this review of the global literature explore these risks and show a growing body of evidence that persistent, low concentrations of these insecticides pose serious risks of undesirable environmental impacts
