The use of agricultural neonicotinoid insecticides has sub-lethal chronic effects on bees that are more prevalent than acute toxicity. Among these insecticides, thiacloprid, a commonly used compound ...with low toxicity, has attracted significant attention due to its potential impact on the olfactory and learning abilities of honeybees. The effect of sub-lethal larval exposure to thiacloprid on the antennal activity of adult honeybees (
L.) is not yet fully understood. To address this knowledge gap, laboratory-based experiments were conducted in which honeybee larvae were administered thiacloprid (0.5 mg/L and 1.0 mg/L). Using electroantennography (EAG), the impacts of thiacloprid exposure on the antennal selectivity to common floral volatiles were evaluated. Additionally, the effects of sub-lethal exposure on odor-related learning and memory were also assessed. The results of this study reveal, for the first time, that sub-lethal larval exposure to thiacloprid decreased honeybee antenna EAG responses to floral scents, leading to increased olfactory selectivity in the high-dose (1.0 mg/L) group compared to the control group (0 mg/L
. 1.0 mg/L:
= 0.042). The results also suggest that thiacloprid negatively affected odor-associated paired learning acquisition, as well as medium-term (1 h) (0 mg/L
. 1.0 mg/L:
= 0.019) and long-term memory (24 h) (0 mg/L
. 1.0 mg/L:
= 0.037) in adult honeybees. EAG amplitudes were dramatically reduced following R-linalool paired olfactory training (0 mg/L
. 1.0 mg/L:
= 0.001; 0 mg/L
. 0.5 mg/L:
= 0.027), while antennal activities only differed significantly in the control between paired and unpaired groups. Our results indicated that exposure to sub-lethal concentrations of thiacloprid may affect olfactory perception and learning and memory behaviors in honeybees. These findings have important implications for the safe use of agrochemicals in the environment.
Abstract
Despite many studies have revealed that developing honey bee (
Apis mellifera
) larvae are posting a high risk on exposure to insecticides, the toxicology information on bee larvae remain ...limited. The present study demonstrated the first assessment of the effects of no observed adverse effect concentration (NOAEC) of carbaryl (CR) and acetamiprid (ACE) on transcriptome and metabolome in honeybee larvae reared in vitro. Chronic exposure to carbaryl caused transcriptional disorders associated with oxidative stress. In addition, a series of metabolic homeostasis were disrupted by carbaryl stress, such amino acid metabolism, purine and pyrimidine metabolism and flavone and flavonol biosynthesis. The activities of enzymic biomarkers including GST, P450, CAT, AChE and SOD were not influenced by ACE stress, while the CR exposure slightly decreased the activity of CAT and SOD. Our results clearly show that ACE and CR display different potential to modulate transcriptome and metabolome associated with their different toxicity against bee larvae.
Chlorothalonil and acetamiprid are chemical pesticides commonly used in agricultural production and have been shown to have negative effects on bee's fitness. Despite many studies have revealed that ...honey bee (
L.) larvae are posting a high risk on exposure to pesticides, but the toxicology information of chlorothalonil and acetamiprid on bee larvae remain limited.
The no observed adverse effect concentration (NOAEC) of chlorothalonil and acetamiprid for honey bee larvae were 4 μg/mL and 2 μg/mL, respectively. Except for CarE, the enzymic activities of GST and P450 were not influenced by chlorothalonil at NOAEC, while chronic exposure to acetamiprid slightly increased the activities of the three tested enzymes at NOAEC. Further, the exposed larvae showed significantly higher expression of genes involved in a series of different toxicologically relevant process following, including caste development (
(GB44905),
(GB55425),
(GB47037),
(GB11637) and
(GB10174)), immune system response (
(GB18323),
(GB19392),
(GB50418)), and oxidative stress response (P450, GSH, GST, CarE).
Our results suggest that the exposure to chlorothalonil and acetamiprid, even at concentrations below the NOAEC, showed potentially effects on bee larvae's fitness, and more important synergistic and behavioral effects that can affect larvae fitness should be explored in the further.
Tropilaelaps mercedesae is one of the most problematic honey bee parasites and has become more threatening to the beekeeping industry. Tropilaelaps can easily parasitize immature honey bees (larvae ...and pupae) and have both lethal and sublethal effects on the individual worker bees. Our study for the first time experimentally assessed the effects of T. mercedesae on olfactory learning, flight ability, homing ability as well as transcriptional changes in parasitized adult honey bees. T. mercedesae infestation had negative impacts on olfactory associated function, flight ability, and homing rate. The volume of the mushroom body significantly increased in infested honey bees, which may be correlated to the lower sucrose responsiveness as well as lower learning ability in the infested bees. The gene expression involved in immune systems and carbohydrate transport and metabolism were significantly different between infested bees and non-infested bees. Moreover, genes function in cell adhesion play an essential role in olfactory sensory in honey bees. Our findings provide a comprehensive understanding of European honey bees in response to T. mercedesae infestation, and could be used to further investigate the complex molecular mechanisms in honey bees under parasitic stress.
Abstract
The greater wax moth (GWM),
Galleria mellonella
(Lepidoptera: Pyralidae), is a major bee pest that causes significant damage to beehives and results in economic losses.
Bacillus ...thuringiensis
(Bt) appears as a potential sustainable solution to control this pest. Here, we develop a novel Bt strain (designated BiotGm) that exhibits insecticidal activity against GWM larvae with a LC
50
value lower than 2 μg/g, and low toxicity levels to honey bee with a LC
50
= 20598.78 μg/mL for larvae and no observed adverse effect concentration = 100 μg/mL for adults. We design an entrapment method consisting of a lure for GWM larvae, BiotGm, and a trapping device that prevents bees from contacting the lure. We find that this method reduces the population of GWM larvae in both laboratory and field trials. Overall, these results provide a promising direction for the application of Bt-based biological control of GWM in beehives, although further optimization remain necessary.
The eastern honey bee (
Apis cerana
) is an important managed pollinator adapted to forest landscapes in China and other Asian countries adjacent to China. Eastern honey bee is thought to be ...threatened by forage deficiency due to deforestation; however, limited research is available to support this assumption. Our study will determine whether varying subtropical forests, the major shelter of eastern honey bees in China, affects bee forage and health. We placed hives at locations with high (HFC), medium (MFC), or low forest cover (control) and monitored the forage collection and bee population in the summer and fall. We found that available forage and bee population size (including larvae, capped pupae, and adult bees) were not significantly different among control, MFC, and HFC. Forage and larvae and pupae amount under control and MFC tended to be more abundant and larger compared with HFC. Though forage was not reduced by low forest cover, eastern honey bees at the control locations died potentially due to disease transmission and pesticide use in adjacent crops as well as vandalism. This study suggested the medium forest cover may be a compromise strategy to insure the forage availability and buffer colonies from environmental stress. Further study needs to confirm the application of this strategy.
Honey bees have significant ecological and economic value as important pollinators, but they are continuously exposed to various environmental stressors, including insecticides, which can impair ...their health and cause colony decline. (1) Background: Cognitive abilities are vital for the functional maintenance of honey bees; however, it remains unknown if chronic, low-dose exposure to thiacloprid during the larval stage impairs the cognitive abilities of emerged adult honey bees. (2) Methods: To explore this question, honey bee larvae were fed 0, 0.5, and 1.0 mg/L thiacloprid during their developmental phase. Then, the cognitive (i.e., olfactory learning and memory) abilities of adult honey bees were quantified to assess the delayed impacts of early-stage thiacloprid exposure on adult honey bee cognition. Neural apoptosis and transcriptomic level were also evaluated to explore the neurological mechanisms underlying these effects. (3) Results: Our results revealed that chronic larval exposure to sublethal thiacloprid impaired the learning and memory abilities of adult honey bees by inducing neuronal apoptosis and transcriptomic alterations. (4) Conclusions: We highlighted a previously unknown impairment caused by thiacloprid in honey bees.
(
)-β-Ocimene was the only volatile chemical found to be emitted by whole, live worker larvae of
L. when sampling in the vapor phase. In addition to (
)-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.
Effects of glyphosate on survival, developmental rate, larval weight, and midgut bacterial diversity of Apis mellifera were tested in the laboratory. Larvae were reared in vitro and fed diet ...containing glyphosate 0.8, 4, and 20 mg/L. The dependent variables were compared with negative control and positive control (dimethoate 45 mg/L). Brood survival decreased in 4 or 20 mg/L glyphosate treatments but not in 0.8 mg/L, and larval weight decreased in 0.8 or 4 mg/L glyphosate treatments. Exposure to three concentrations did not affect the developmental rate. Furthermore, the intestinal bacterial communities were determined using high-throughput sequencing targeting the V3–V4 regions of the 16S rDNA. All core honey bee intestinal bacterial phyla such as Proteobacteria (30.86%), Firmicutes (13.82%), and Actinobacteria (11.88%) were detected, and significant changes were found in the species diversity and richness in 20 mg/L glyphosate group. Our results suggest that high concentrations of glyphosate are deleterious to immature bees.
The acute and chronic toxicity of 3 common pesticides, namely, amitraz, chlorpyrifos and dimethoate, were tested in Apis mellifera and Apis cerana. Acute oral toxicity LC50 values were calculated ...after 24 h of exposure to contaminated syrup, and chronic toxicity was tested after 15 days of exposure to 2 sublethal concentrations of pesticides. The toxicity of the tested pesticides to A. mellifera and A. cerana decreased in the order of dimethoate > chlorpyrifos > amitraz. A. mellifera was slightly more sensitive to chlorpyrifos and dimethoate than A. cerana, while A. cerana was more sensitive to amitraz than A. mellifera. Chronic toxicity tests showed that 1.0 mg/L dimethoate reduced the survival of the two bee species and the food consumption of A. mellifera, while 1.0 mg/L amitraz and 1.0 mg/L chlorpyrifos did not affect the survival or food consumption of the two bee species. The treatment of syrup with amitraz at a concentration equal to 1/10th of the LC50 value did not affect the survival of or diet consumption by A. mellifera and A. cerana; however, chlorpyrifos and dimethoate at concentrations equal to 1/10th of their respective LC50 values affected the survival of A. cerana. Furthermore, intestinal bacterial communities were identified using high-throughput sequencing targeting the V3V4 regions of the 16S rDNA gene. All major honey bee intestinal bacterial phyla, including Proteobacteria (62.84%), Firmicutes (34.04%), and Bacteroidetes (2.02%), were detected. There was a significant difference in the microbiota species richness of the two species after 15 days; however, after 30 days, no significant differences were found in the species diversity and richness between A. cerana and A. mellifera exposed to 1.0 mg/L amitraz and 1.0 mg/L chlorpyrifos. Overall, our results confirm that acute toxicity values are valuable for evaluating the chronic toxicity of these pesticides to honey bees.
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•Apis mellifera was more sensitive to chlorpyrifos and dimethoate than Apis cerana.•Amitraz at a concentration of 7.8 mg/L impacted Apis cerana survival.•Chlorpyrifos at a concentration of 3.0 mg/L impacted Apis cerana survival.•Dimethoate at a concentration of 1.0 mg/L impacted both Apis mellifera and Apis cerana survival.•There was a significant difference in microbiota species richness among treatments at day 15.
Apis mellifera and Apis cerana showed different sensitivities to 3 pesticides and differential midgut bacterial richness between treatments at day 15.
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