Impaired Olfactory Associative Behavior of Honeybee Workers Due to Contamination of Imidacloprid in the Larval Stage

Abstract

The residue of imidacloprid in the nectar and pollens of the plants is toxic not only to adult honeybees but also the larvae. Our understanding of the risk of imidacloprid to larvae of the honeybees is still in a very early stage. In this study, the capped-brood, pupation and eclosion rates of the honeybee larvae were recorded after treating them directly in the hive with different dosages of imidacloprid. The brood-capped rates of the larvae decreased significantly when the dosages increased from 24 to 8000 ng/larva. However, there were no significant effects of DMSO or 0.4 ng of imidacloprid per larva on the brood-capped, pupation and eclosion rates. Although the sublethal dosage of imidacloprid had no effect on the eclosion rate, we found that the olfactory associative behavior of the adult bees was impaired if they had been treated with 0.04 ng/larva imidacloprid in the larval stage. These results demonstrate that a sublethal dosage of imidacloprid given to the larvae affects the subsequent associative ability of the adult honeybee workers. Thus, a low dose of imidacloprid may affect the survival condition of the entire colony, even though the larvae survive to adulthood.

A neonicotinoid, imidacloprid, impairs honey bee aversive learning of simulated predation

“…Honey bee nAChRs play an important role in cholinergic neural signaling, and bees fed sublethal doses of imidacloprid downregulate nAChRs in their brains . Not surprisingly, imidacloprid has a wide variety of effects: brain cell death , decreased food uptake (Ramirez-Romero et al, 2005), reduced motor function (Lambin et al, 2001;Williamson et al, 2014), diminished hive entrance activity (Decourtye et al, 2004), impaired foraging (Schneider et al, 2012), impaired visual learning (Han et al, 2010), decreased predator avoidance (Tan et al, 2014), impaired navigation to the nest Henry et al, 2012) and deficient rewarded olfactory learning (Cresswell, 2011;Yang et al, 2012).…”

“…Olfactory learning therefore facilitates foraging (Giurfa and Sandoz, 2012) and floral constancy, which is important for efficient pollination (Wright and Schiestl, 2009). However, sublethal doses of imidacloprid (Decourtye et al, 2004;Tan et al, 2015;Yang et al, 2012) or a primary metabolic byproduct (Decourtye et al, 2003) significantly impair short-term and longerterm rewarded olfactory learning. Synergistic effects increase this problem.…”

Resistance of developing honeybee larvae during chronic exposure to dietary nicotine

“…Larvae, far from being protected from pesticides in the colony, may thus be chronically exposed to an accumulation of chemical residues with potential additive or synergistic effects. There is evidence for delayed development of larvae reared in comb containing pesticide residues (Wu et al, 2011), and dose-dependent effects on rates of capping, pupation and eclosion were recorded by Yang et al (2012) when they added imidacloprid solutions directly to cells in the hive containing newly emerged larvae.…”

Weight of evidence evaluation of a network of adverse outcome pathways linking activation of the nicotinic acetylcholine receptor in honey bees to colony death

“…Yang et al (2012) provided evidence that exposure of bee larvae to 0.04 μg/L imidacloprid solution added directly to the brood cell resulted in impaired olfactory associative behavior, as measured by PER, in adult bees. Exposure of adult bees to imidacloprid has also been reported to impair memory utilizing the PER procedure.…”