Survival for Immunity: The Price of Immune System Activation for Bumblebee Workers

TLDR

Parasites are often tolerated because the immune system controls infection, yet immune activation can itself lower host fitness, a cost that is usually masked by compensatory resource intake. The study induced immune responses in Bombus terrestris workers by injecting lipopolysaccharides and micro‑latex beads while keeping them starved to prevent compensatory feeding. Induced workers exhibited a 50–70 % reduction in survival relative to controls.

Abstract

Parasites do not always harm their hosts because the immune system keeps an infection at bay. Ironically, the cost of using immune defenses could itself reduce host fitness. This indirect cost of parasitism is often not visible because of compensatory resource intake. Here, workers of the bumblebee, Bombus terrestris , were challenged with lipopolysaccharides and micro–latex beads to induce their immune system under starvation (i.e., not allowing compensatory intake). Compared with controls, survival of induced workers was significantly reduced (by 50 to 70%).