Most people know how vaccination works: our adaptive immune system (i.e. immune memory) generates specific antibodies, protecting against re-infection by the same pathogen. Invertebrates cannot produce antibodies, but many insects exhibit a form of immune memory in addition to innate immunity. How does this memory evolve? We infected flour beetles with a pathogen (Bacillus thuringiensis) that imposes over 50% mortality. We observed two mutually exclusive strategies: in ~10 generations, beetles evolved either specific immune memory or improved innate immunity. This first report of experimental evolution of insect immune memory raises exciting questions about its costs, underlying mechanisms, and evolutionary impact.

– Deepa Agashe, Imroze Khan

See the online preprint here