Joint effects of cadmium and copper on Apis mellifera forgers and larvae

Ning Di,Kai Zhang,Kristen R Hladun,Michael Rust,Ya-Feng Chen,Zheng-Yang Zhu,Tong-Xian Liu,John T Trumble

doi:10.1016/j.cbpc.2020.108839

Abstract

Honey bees (Apis mellifera L.) are important ecological and agricultural resources. They are among the most widely available pollinators and provide products as well as services. Unfortunately, honey bee populations are susceptible to several environmental threats, including heavy metal exposure. Honey bees can be exposed to heavy metals when foraging on contaminated honey and pollen resources, and in some cases by airborne exposure. We studied the joint acute and chronic effects of cadmium (Cd) and copper (Cu) on A. mellifera. A 1:1 solution of the two heavy metals increased larval developmental duration and the mortality of both larvae and foragers in a dose-dependent way, decreased forager feeding, increased body metal burdens, and disrupted the sucrose response behavior of foragers. In combination, Cd and Cu demonstrated a weakly synergistic effect on foragers, but for larvae an initially antagonistic effect at low doses changed to strongly synergistic response at higher concentrations. The sucrose response threshold of foragers decreased significantly when they were dosed with increasing concentrations of the metal mixtures. Overall, the fitness of honey bee larvae and foragers is detrimentally affected when these metals co-occur.

Highlights

In recent years, metal pollution has become an increasingly important ecological problem around the world (Li et al, 2018; Wan et al, 2019; Zwolak et al, 2019)
Some reports indicate insect cell ultrastructure and genetic material can be adversely affected by heavy metals, inducing cell apoptosis that can disrupt cell vigor, cell proliferation, and result in mutation (Stolpe et al, 2017)
Regardless, when foragers have greater mortality and become less efficient, when foraging resources are limited by contamination, and when larval relative growth indices (RGI) is reduced, negative colony level effects can be expected

Summary

Introduction

Metal pollution has become an increasingly important ecological problem around the world (Li et al, 2018; Wan et al, 2019; Zwolak et al, 2019). Heavy metals are stable in the environment, which allows potential accumulation to toxic levels in both water supplies and terrestrial habitats (Nriagu and Pacyna, 1988). Heavy metals are difficult to eliminate once present in soil or water, and reportedly cause irreversible damage to survival, feeding, growth, and behavior of organisms, including honey bees (Nicholson et al, 2003; Hongxia et al, 2010; Di et al, 2016). Heavy metal ions can enter insect bodies during respiration, via air deposition or dislodgeble residues on surfaces, or through ingestion during feeding or grooming (Mogren and Trumble, 2010; Ali et al, 2019; Dabour et al, 2019)

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