Impact of transgenerational immune priming on the defence of insect eggs against parasitism

Insects are known to prime the immune state of their offspring. However, although the beginning of insect life, the egg stage, is often greatly endangered by parasitism, no knowledge is available regarding whether transgenerational immune priming improves the immune responses of insect eggs to actual parasitoid attacks. Our study revealed suppression of the development of parasitoids in transgenerationally immune-primed Manduca sexta eggs and reduced emergence rates of parasitoids from these eggs. The higher defence efficiency of immune-primed M. sexta eggs against parasitoids was in agreement with the increased antibacterial activity and phenoloxidase activity of these eggs in response to parasitism compared to the eggs of control parents. Our study showed that immunochallenged insect parents could enable their offspring already in the egg stage to defend more efficiently against parasitic invaders. We discuss whether M. sexta benefits from transgenerational immune priming of eggs by limiting the population growth of egg parasitoids.