Review on Sublethal Effects of Environmental Contaminants in Honey Bees (Apis mellifera), Knowledge Gaps and Future Perspectives

Abstract

Honey bees and the pollination services they provide are fundamental for agriculture and biodiversity. Agrochemical products and other classes of contaminants, such as trace elements and polycyclic aromatic hydrocarbons, contribute to the general decline of bees’ populations. For this reason, effects, and particularly sublethal effects of contaminants need to be investigated. We conducted a review of the existing literature regarding the type of effects evaluated in Apis mellifera, collecting information about regions, methodological approaches, the type of contaminants, and honey bees’ life stages. Europe and North America are the regions in which A. mellifera biological responses were mostly studied and the most investigated compounds are insecticides. A. mellifera was studied more in the laboratory than in field conditions. Through the observation of the different responses examined, we found that there were several knowledge gaps that should be addressed, particularly within enzymatic and molecular responses, such as those regarding the immune system and genotoxicity. The importance of developing an integrated approach that combines responses at different levels, from molecular to organism and population, needs to be highlighted in order to evaluate the impact of anthropogenic contamination on this pollinator species.

First application of an Integrated Biological Response index to assess the ecotoxicological status of honeybees from rural and urban areas

“…To the best of our knowledge, few papers evaluated immune system alterations related to contamination in honeybees. As reported in a recent review by Di Noi et al ( 2021 ), insecticides are able to affect the immune system by altering the expression of different related genes (Abbo et al 2017 ; Christen et al 2019 ; Morimoto et al 2011 ; Tesovnik et al 2017 ; Zhu et al 2020 ), hemocytes density, and antimicrobial activity (Brandt et al 2016 ). However, as shown in studies performed on different taxa (Mdaini et al 2019 ; Wu et al 2007 ), chemical compounds and heavy metals could modify bees’ immune system response.…”

Combined Effects of Pesticides and Electromagnetic-Fields on Honeybees: Multi-Stress Exposure

“…The use of a battery of biomarkers on two life stages (pupae and worker bees) allowed the study of these parameters in "stress conditions" (exposure sites) but also in "physiological conditions" (control site). In the literature, biomarkers were already used to test different stresses (urban pollution and pesticides) on Apis mellifera both in the field [67][68][69][70][71][72] and in laboratory [73][74][75]. In the field, a reference station is always chosen away from anthropogenic sources but close enough to the experimental sites to have a direct comparison [68][69][70]74].…”

Varroa destructor from the Laboratory to the Field: Control, Biocontrol and IPM Perspectives—A Review

“…Several works took this aspect into account while testing different molecules or agents against the acari and showed a customised response per location [29,222,259]. To improve our knowledge about the host-parasite dynamic, we still need further research including these aspects to get the full picture from the molecular scale to the population dynamic [260].…”