Temporal dynamics of whole body residues of the neonicotinoid insecticide imidacloprid in live or dead honeybees

Abstract

In cases of acute intoxication, honeybees often lay in front of their hives for several days, exposed to sunlight and weather, before a beekeeper can take a sample. Beekeepers send samples to analytical laboratories, but sometimes no residues can be detected. Temperature and sun light could influence the decrease of pesticides in bee samples and thereby residues left for analysis. Moreover, samples are usually sent via normal postal services without cooling. We investigated the temporal dynamics of whole-body residues of imidacloprid in live or dead honeybees following a single-meal dietary exposure of 41 ng/bee under various environmental conditions, such as freezing, exposure to UV light or transfer of individuals through the mail system. Immobile, “dead” looking honeybees recovered from paralysis after 48 hours. The decrease of residues in living but paralysed bees was stopped by freezing (= killing). UV light significantly reduced residues, but the mode of transport did not affect residue levels. Group feeding increased the variance of residues, which is relevant for acute oral toxicity tests. In conclusion, elapsed time after poisoning is key for detection of neonicotinoids. Freezing before mailing significantly reduced the decrease of imidacloprid residues and may increase the accuracy of laboratory analysis for pesticides.

Fipronil pesticide as a suspect in historical mass mortalities of honey bees

“…In principle, similar reversible ligand-receptor binding therefore appears likely in bees. Second, the timescale of postexposure recovery (24-48 h) in honey bees (13) and bumble bees (18,19) coincides with the timescale of metabolic elimination (elimination half-life ∼ 24 h) (13,14,19), which logically suggests that imidacloprid increasingly dissociates from its receptors as detoxification reduces the concentration of its unbound form. Taken together, this collection of evidence indicates that imidacloprid binds reversibly to its receptors in bees and, if so, toxicodynamic-kinetic theory relating to toxicants with a short elimination half-life (15) predicts the absence of TRT in experimental exposures to imidacloprid, just as we observed in the present study.…”

“…Further, it appears that imidacloprid does not accumulate locally at its target sites by binding irreversibly to receptors in the insect nervous system. Instead, rapid postexposure recovery is observed in honey bees (13) and other insects including cockroaches (16), termites (17), and bumble bees (18,19), which clearly indicates reversible binding. Taken together, this evidence suggests that it is unlikely that even a sustained exposure to dietary imidacloprid at environmentally realistic levels can be the cause of mass fatalities.…”

“…Potentially, an insecticide that is present as trace dietary residues eventually may accumulate to a lethal level during a sustained exposure, which is possible in bees because their adult lifespan and the blooming period of mass-flowering crops like sunflower and canola both extend over several weeks. However, honey bees clear ingested imidacloprid rapidly from their bodies (92% within 48 h) (13) and the elimination half-life of imidacloprid and its toxic metabolites is ∼24 h (14). In theory, the bodily concentration of an ingested toxicant reaches steady state in ∼4 elimination half-lives (15), so imidacloprid is unlikely to be bioaccumulative during exposures at an ecologically relevant timescale, which is measured in weeks.…”

Contact application of neonicotinoids suppresses the predation rate in different densities of prey and induces paralysis of common farmland spiders

“…The observation of paralysis in response to neonicotinoids is actually very common in honey bees, which are often found immobile in front of hives in response to the application of neonicotinoids 43,44 . A recent study reported that the kinetics of paralysis induction is concentration dependent, with concentrations increased by one order of magnitude decreasing the time from exposure to paralysis from 36 hours to only a single hour 45 . The paralytic effects of neonicotinoids are not limited to honey bees.…”

Effects of cage volume and bee density on survival and nutrient intake of honeybees (Apis mellifera L.) under laboratory conditions

“…Social interactions of adult worker honeybees include trophallaxis (feeding each other, reviewed by Crailsheim 1992), the waggle dance directing other bees to forage (von Frisch and Lindauer 1956) and huddling together in groups to thermoregulate (Lindauer 1955). These social interactions shape individual honeybee behaviour, for example, nutrient gathering behaviour of forager bees is influenced by the composition of the trophallactic secretions received from nurse bees (Camazine et al 1998;Schott et al 2017) or thermoregulation within the brood nest (Basile et al 2008). This means that in a hive social interactions are necessary for bees to regulate colony temperature, find forage and care for young.…”