Abstracts (first author)
External vs. internal immune defence in the Red Flour Beetle (Tribolium castaneum)?
The red flour beetle, Tribolium castaneum, secretes quinones that control the microbial flora in the surrounding environment. These secretions act as an external immune defense that provides protection against pathogens. At high concentrations, however, these secretions are harmful to the host itself, and selection may thus have optimized the level of expression under natural conditions. Here we show that the expression of external immunity responded to selection during experimental evolution within a few generations. At the same time, one component of internal immune defense (phenoloxidase activity) was compromised in beetles selected for either high or low external defenses. Protection against a natural pathogen was lacking in flour obtained from beetle lines selected for low amounts of secretions. Altogether, this suggests that external and internal immune defenses work together efficiently under natural conditions, while every manipulation on the side of external immune defense comes with costs to the internal immune defense.