Burden et al. 2019 - honey-bee feeding behavior after metal-spiked sucrose

Burden and colleagues tested whether worker honey bees detected, rejected, or changed sucrose responsiveness after acute exposure to cadmium-, copper-, and lead-contaminated sucrose. This is in-scope a4 toxicology and animal-feeding exposure evidence for metals in pollinator food resources, not honey occurrence data.

Key numbers

The paper tested cadmium chloride and lead chloride at 0.001 mg/L, 0.01 mg/L, 0.1 mg/L, 1 mg/L, and 10 mg/L in 1 M sucrose. Copper chloride was tested at 0.002 mg/L, 0.02 mg/L, 0.2 mg/L, 2 mg/L, and 20 mg/L in 1 M sucrose. The authors state these concentrations were comparable to or lower than concentrations found in contaminated environments and measured in floral parts of plants grown in contaminated soils.

Assay sample sizes were:

For cadmium, antennal stimulation showed no difference between sucrose and sucrose plus cadmium for any tested concentration (SOLUTION: chi2 = 0.384, p = 0.535; CONCENTRATION: chi2 = 15.975, p = 0.003). Proboscis stimulation also showed no significant concentration effect on consumption of sucrose and sucrose plus cadmium (CONCENTRATION: chi2 = 2.033, p = 0.730; SOLUTION: chi2 = 2.315, p = 0.128), although the authors describe a non-significant reduction at 1 mg/L and 10 mg/L.

For copper, antennal stimulation showed significant rejection of sucrose plus copper at every tested concentration. The paper reports pairwise p < 0.001 for 0.002 mg/L, 0.02 mg/L, 0.2 mg/L, 2 mg/L, and 20 mg/L compared with uncontaminated sucrose. Proboscis stimulation did not show an effect of copper on contaminated-sucrose consumption (CONCENTRATION: chi2 = 2.003, p = 0.730; SOLUTION: chi2 = 2.315, p = 0.128).

For lead, antennal stimulation showed a significant concentration effect and solution-by-concentration interaction (CONCENTRATION: chi2 = 51.733, p < 0.001; SOLUTION: chi2 = 4.915, p = 0.027; CONCENTRATION x SOLUTION: chi2 = 16.011, p = 0.003). At 0.001 mg/L, the percentage of bees exhibiting proboscis extension reflex to lead-contaminated sucrose was lower than to uncontaminated sucrose (p = 0.016), while 0.01 mg/L, 0.1 mg/L, 1 mg/L, and 10 mg/L did not differ from sucrose-only trials (all p = 1.000).

For lead proboscis stimulation, concentration and solution both affected consumption (CONCENTRATION: chi2 = 10.169, p = 0.038; SOLUTION: chi2 = 32.415, p < 0.001). Consumption of lead-contaminated sucrose was lower than uncontaminated sucrose at 0.001 mg/L (p < 0.001), 0.01 mg/L (p = 0.019), 0.1 mg/L (p < 0.001), and 1 mg/L (p < 0.001), but did not differ at 10 mg/L (p = 1.000).

In the sucrose-response-threshold assay, cadmium pretreatment did not significantly change sucrose discrimination (CONCENTRATION: chi2 = 7.367, p = 0.195). Copper pretreatment also did not significantly change sucrose responsiveness (CONCENTRATION: chi2 = 5.405, p = 0.368). Lead pretreatment produced a significant concentration-by-sucrose interaction (CONCENTRATION x SUCROSE%: chi2 = 43.731, p = 0.012); bees pretreated with 0.01 mg/L and 1 mg/L lead showed higher responsiveness at 1% sucrose (p = 0.041 and p = 0.032, respectively).

The paper cites major agricultural-region soil concentration ranges in the United States as cadmium < 0.01-2 mg/kg, copper < 0.06-495 mg/kg, and lead < 1.0-135 mg/kg.

Methods (brief)

The study collected pollen-forager worker honey bees at colony entrances, anesthetized them in an ice-water bath, restrained them in harnesses, fed them 1 M sucrose, and held them about 24 h before assays. Antennal assays recorded proboscis extension reflex after stimulation with water, sucrose, water, and sucrose plus metal, repeated across increasing metal concentrations. Proboscis assays recorded whether bees consumed a 0.6 microliter droplet after antennal stimulation. Sucrose-response-threshold assays fed bees 20 microliters of sucrose or sucrose plus metal 2 h before testing response to increasing sucrose concentrations from 0.1% to 30%. Analyses used logistic and multinomial logistic generalized estimating equations in IBM SPSS version 23.

Implications

Certification: These are metal-spiked sucrose and bee-behavior data. They must not be used as honey, pollen, propolis, or wax occurrence values.

Courses: Useful downstream-effect example for pollinator exposure because it distinguishes metal-specific rejection and palatability responses rather than treating “heavy metals” as a single behavioral class.

App: Context only. The source can inform honey-supply-chain and pollinator-health narratives but does not provide a consumer-product concentration.

Wiki pages this source may touch

• cadmium
• copper
• lead

Verification notes

Recovered from skip:not-food-occurrence under the 2026-06-10 inclusion-by-default rule. The old skip treated the paper as out of scope because it measured honey-bee feeding behavior after metal-spiked sucrose rather than honey occurrence. On reading, it is in-scope a4 toxicology and animal-feeding exposure evidence.

Numbers were checked against the abstract, Results, figure captions, Methods, and Discussion in the extracted PDF. Metal forms are recorded as total Cd, Cu, and Pb in the wiki frontmatter because the experimental salts were cadmium chloride, copper chloride, and lead chloride, and the paper does not report consumer-product speciation. Products and ingredients are intentionally empty. sucrose-solution is a matrix term added for this controlled feeding assay; it is not an occurrence-product route.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.