Abstract:
There is clear evidence for sublethal effects of neonicotinoid insecticides
on non-target ecosystem service-providing insects. However, their possible
impact on male insect reproduction is currently unknown, despite the key
role of sex. Here, we show that two neonicotinoids (4.5 ppb thiamethoxam
and 1.5 ppb clothianidin) significantly reduce the reproductive capacity of
male honeybees (drones), Apis mellifera. Drones were obtained from colonies
exposed to the neonicotinoid insecticides or controls, and subsequently maintained
in laboratory cages until they reached sexual maturity. While no
significant effects were observed for male teneral (newly emerged adult) body
mass and sperm quantity, the data clearly showed reduced drone lifespan, as
well as reduced sperm viability (percentage living versus dead) and living
sperm quantity by 39%. Our results demonstrate for the first time that neonicotinoid
insecticides can negatively affect male insect reproductive capacity, and
provide a possible mechanistic explanation formanaged honeybee queen failure
andwild insect pollinator decline. Thewidespread prophylactic use of neonicotinoids
may have previously overlooked inadvertent contraceptive effects on
non-target insects, thereby limiting conservation efforts.
