Caterpillars of the tobacco hornworm (Manduca sexta), as the name suggests, specialize on eating nicotine containing plants. Normally, nicotine is an effective plant defense against herbivores as it poisons various animals by interrupting neural mechanisms associated with muscle movement. Tobacco hornworms, however, can handle doses of nicotine that are lethal to herbivores that do not specialize on eating plants with this defense. There is also evidence that they co-opt the nicotine poison for their own defense against predators but it was unclear how this was done since they do not store nicotine anywhere in their body. In a study looking at interactions with a predatory wolf spider (Camptocosa parallela), it was shown that these larvae release the nicotine they eat through their spiracle, a respiratory opening that allows gases to diffuse in and out of their tracheal system, which stops wolf spiders from eating them after they’ve been captured. In other words, tobacco hornworms use their bad tobacco-ey breath to ward off certain predators!
Sketch contributed by Amelia Munson
Fact Contributed by Adrian Perez
Source: Kumar, P., Pandit, S.S., Steppuhn, A. and Baldwin, I.T., 2014. Natural history-driven, plant-mediated RNAi-based study reveals CYP6B46’s role in a nicotine-mediated antipredator herbivore defense. Proceedings of the National Academy of Sciences, 111(4), pp.1245-1252.