The new diamide insecticide chlorantraniliprole compromises honey bee locomotion through alterations of brain and muscle calcium channels.

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Voltage-gated sodium channels from the bees Apis mellifera and Bombus terrestris are differentially modulated by pyrethroid insecticides

Recent experimental and in-field evidence of the deleterious effects of insecticides on the domestic honey bee Apis mellifera have led to a tightening of the risk assessment requirements of these products, and now more attention is being paid to their sublethal effects on other bee species. In addition to traditional tests, in vitro and in silico approaches may become essential tools for a comprehensive understanding of the impact of insecticides on bee species. Here we present a study in which electrophysiology and a Markovian multi-state modelling of the voltage-gated sodium channel were used to measure the susceptibility of the antennal lobe neurons from Apis mellifera and Bombus terrestris, to the pyrethroids tetramethrin and esfenvalerate. Voltage-gated sodium channels from Apis mellifera and Bombus terrestris are differentially sensitive to pyrethroids. In both bee species, the level of neuronal activity played an important role in their relative sensitivity to pyrethroids. This work supports the notion that honey bees cannot unequivocally be considered as a surrogate for other bee species in assessing their neuronal susceptibility to insecticides

Evidence for locomotor deficits after exposure to a sublethal dose (SLD_48h) of a pyrethroid or a neonicotinoid but not a phenylpyrazole.

<p><b>A</b>, The average (± S.E.M) relative distance covered by young bees is significantly decreased 6±2h after exposure to either a SLD_48h of cypermethrin (2.5 ng/bee), tau-fluvalinate (33 ng/bee) or tetramethrin (70 ng/bee). <b>B</b>, A significant decrease in distance is observed after exposure to a SLD_48h of thiamethoxam (3.8 ng/bee) as well. <b>C</b>, The relative distance covered by bees after exposure to a SLD_48h of fipronil (0.5 ng/bee) is similar to the distance covered by control bees. In the case of fipronil, whereas early deleterious effects cannot be evidenced by the locomotion assay, an increased mortality is observed five days after exposure. For cypermethrin, n = 19 control and n = 20 exposed bees respectively. For tau-fluvalinate, n = 12 control and n = 19 exposed bees respectively. For tetramethrin, n = 20 control and n = 20 exposed bees respectively. For thiamethoxam, n = 19 control and n = 19 exposed bees respectively. For fipronil, n = 19 control and n = 20 exposed bees respectively.</p

Video tracking of bees using a vertical arena.

<p><b>A,</b> Examples of paths followed during 3 minutes by four individual young bees (day 1 after emergence). <b>B,</b> Superimposed paths followed by eighty individual bees. Overall, arena sides were more frequently visited. <b>C,</b> Locomotor ability measured at day 1, 2 and 6 after emergence (bees kept in an incubator). Mean distance (± S.E.M) covered by bees slightly increased from 3.2 to 3.8 meters between day 1 and 2 (p<0.01, n = 138 and 63 respectively) and did not significantly further increase as shown at 6 days after emergence (n = 38).</p