Changes in innate immune response and detoxification in Melipona quadrifasciata (Apinae: Meliponini) on oral exposure to azadirachtin and spinosad

Abstract

Exposure to agrochemicals and pathogens has been indicated as critical factors of declining pollinator populations, including species of native tropical bees. In the present study, we investigated the sublethal effects of acute oral exposure to azadirachtin and spinosad bioinsecticides on the expression of immunity-related genes and the number of hemocytes in uninfected and Escherichia coli -infected workers of the stingless bee Melipona quadrifasciata . Expression of the immune-related gene vitellogenin decreased and the number of circulating hemocytes increased in bioinsecticide-exposed uninfected bees and in unexposed E. coli -infected bees as compared with unexposed uninfected bees. Our results show that though bioinsecticides are considered safe, contamination by sublethal doses of azadirachtin and spinosad can interfere with the immune system of bees.bioinsecticides / hemocytes / spinosad / stingless bees / vitellogenin

The Insecticide Imidacloprid Decreases Nannotrigona Stingless Bee Survival and Food Consumption and Modulates the Expression of Detoxification and Immune-Related Genes

“…We found that repeated exposure to imidacloprid at lesser concentrations altered the expression of immune-related genes (abaecin, defensin1, and hymenopteacin); moreover, significant treatment x time interaction terms were observed, showing that gene expression varied over time. These findings are not consistent with the reports of previous studies that abaecin expression in A. mellifera adults was unaffected by exposure to coumaphos, tau-fluvalinate, imidacloprid, and spinosad [85][86][87] as well as in M. quadrifasciata workers exposed to azadirachtin or spinosad insecticides [52]. However, similar to our findings, a significant increase in the expression of AMP genes abaecin, apidaecin, and hymenoptaecin, was observed in bumble bees exposed to moderate to high concentrations of imidacloprid, and responses were time and dose dependent [88].…”

“…Pesticide exposure has been shown to lower global AMP production, further compromising an already frail immune system [49][50][51]. Unfortunately, there is little research on the characterization of detoxification systems and immune responses in stingless bees [52] with which to understand their response and defense against diverse environmental stressors.…”

Biopesticides and insect pollinators: Detrimental effects, outdated guidelines, and future directions

“…Sublethal effects were also observed in terms of reduced pupal body mass and deformities at the pupal stage that resulted in deformed adults after molting (Barbosa et al, 2015b). Azadirachtin decreased the expression of the immune-related gene vitellogenin, while increasing the number of circulating hemocytes in exposed workers of the same species (Viana et al, 2020). Azadirachtin was less toxic on P. helleri and S. xanthotricha, exhibiting negligible mortality on adult workers after exposure at the field-recommended concentrations (Tomé et al, 2015).…”

“…Spinosad exposure produced deformed pupae and impaired locomotor and flight ability in emerged adults of M. quadrifasciata (Barbosa et al, 2015b;Piovesan et al, 2020). Exposure of M. quadrifasciata workers also caused a decrease in the expression of the immune-related gene vitellogenin and an increase in the number of circulating hemocytes (Viana et al, 2020). In P. lucii, walking and flight were reduced without alterations of individual body mass and respiration rate (Marques et al, 2020).…”

Are Botanical Biopesticides Safe for Bees (Hymenoptera, Apoidea)?

“…The ingestion of azadiractin caused a reduction in the gene expression of vitellogenin ( Vg ) of M . quadrifasciata workers, infected and uninfected with Escherichia coli [ 156 ]. The same study highlighted an increase in the number of haemocytes in both infected and uninfected bees due to insecticide ingestion [ 156 ].…”