Morphogenetic Alterations in Melipona quadrifasciata anthidioides (Hymenoptera: Apidae) Associated with Pesticides

Larvae of stingless bee Scaptotrigona bipunctata exposed to organophosphorus pesticide develop into lighter, smaller and deformed adult workers

Organophosphorus pesticides such as chlorpyrifos are often used in agriculture due to their broad spectrum of action. However, this insecticide and acaricide is considered highly toxic to the environment and can cause toxicity in nontarget insects such as bees. In addition to adult individuals, immature can also be exposed to residues of this insecticide by larval food. Thus, we investigated the effects of chlorpyrifos concentrations on the larval development of stingless bee Scaptotrigona bipunctata workers reared in vitro. We evaluated four different biomarkers: a) survival, b) development time, c) body mass and d) morphological characteristics (head width, intertegular distance, wing area and proportion of deformed bees). The exposure of the larvae to different doses of chlorpyrifos significantly reduced survival probability but did not cause changes in the development time. Regarding morphometric analysis, bees exposed to chlorpyrifos showed a reduction in body mass and size, and 28% of the emerged adults showed a reduction in wing area and deformations. Therefore, this work shows that S. bipunctata larvae exposed to the sublethal effects of chlorpyrifos are likely to have reduced chances of survival. However, if they emerge, they will be lighter, smaller and less able than equivalent but not exposed workers. These impaired attributes have the potential to compromise the future workforce in colonies exposed to this pesticide.

Effects of insecticides used in strawberries on stingless bees Melipona quadrifasciata and Tetragonisca fiebrigi (Hymenoptera: Apidae)

The use of pesticides is considered one of the most important threats to pollinators, especially since they are widely used in agriculture for pest control. In the last years, several studies have reported severe secondary effects on various bee species, including exotic and native bees. In this study, lethal (mortality) and sublethal (locomotor activity) effects of insecticides and acaricides used in strawberries in Brazil (abamectin, novaluron, spinetoram, and thiamethoxam) were evaluated on the native stingless bees Melipona quadrifasciata and Tetragonisca fiebrigi. The results showed that the effects varied significantly according to the pesticide, type of exposure (oral or topical), and bee species. Through oral exposure, M. quadrifasciata was more susceptible to all insecticides except for abamectin, while in topical exposure, T. fiebrigi was more sensitive. Thiamethoxam followed by spinetoram and abamectin were the most lethal, regardless of species or exposure route; novaluron was not harmful at the highest tested dose. The locomotor activity of bees was altered in the presence of sublethal doses (LC₁₀ and LC₅₀) of all insecticides. Spinetoram and abamectin can be as much as toxic as thiamethoxam against M. quadrifasciata and T. fiebrigi in laboratory experiments. These findings should be confirmed in field experiments to define possibilities to combine pest control and pollinator management. In crops like strawberries, the selectivity of native pollinators should be considered.

The weakest link: Haploid honey bees are more susceptible to neonicotinoid insecticides

Neonicotinoid insecticides are currently of major concern for the health of wild and managed insects that provide key ecosystem services like pollination. Even though sublethal effects of neonicotinoids are well known, there is surprisingly little information on how they possibly impact developmental stability, and to what extent genetics are involved. This holds especially true for haploid individuals because they are hemizygous at detoxification loci and may be more susceptible. Here we take advantage of haplodiploidy in Western honey bees, Apis mellifera, to show for the first time that neonicotinoids affect developmental stability in diploid females (workers), and that haploid males (drones) are even more susceptible. Phenotypic fore wing venation abnormalities and fluctuating wing asymmetry, as measures of developmental instability, were significantly increased under field-realistic neonicotinoid-exposure of colonies. The higher susceptibility of haploid drones suggests that heterozygosity can play a key role in the ability to buffer the sublethal effects of neonicotinoids. Aiming to improve conservation efforts, our findings highlight the urgent need to better understand the role that genetics plays at enabling non-target organisms to cope with insecticide exposure.