A caterpillar creates predator-repelling bad breath by munching on tobacco leaves.
The phenomenon is called "toxic halitosis" and is made possible by the large amount of tobacco the caterpillars ingest, Discovery News reported.
The hornworm moves the ingested nicotine from its gut to the hemolymph (circulatory fluid). The excess nicotine is released when the caterpillar exhales, National Geographic reported.
The discovery of the hornworm's unusual defense marks the first-known creature that uses bad breath as an "advertisement" for their toxicity.
Animals that consume nicotine often experience negative side effects such as problems with breathing and movement; but the hornworm doesn't seem to experience these effects.
"This is why nicotine is such a great defense for plants: it poisons everything that uses muscles to move, and since plants don't have nerves or muscles, it doesn't poison the plant," Ian Baldwin, an ecologist at the Max Planck Institute for Chemical Ecology, told National Geographic.
The researchers found a gene expression, CYP6B46, increased in the "tobacco worms" after they ingested nicotine. The team suggested the gene, which is located in the caterpillar's gut, worked to help raise its resistance to toxic nicotine.
The scientists looked at the effects of three different types of tobacco plant in hopes of discovering more about the gene's function. One plant type had below-average levels of nicotine; the second contained a chemical that "thwarts" CYP6B46; and the third were common plants.
The hornworms that ate the low-nicotine plants were caught by predators more often; this suggests CYP6B46 plays a key role in the caterpillars' ability to ward off predators.
The gene could work to transfer the CYP6B46 to the hemolymph which would allow the caterpillars to breathe out more nicotine, which would help them avoid predators.
The researchers could use this information to genetically engineer plants that are more efficient at repelling predators, Discovery News reported.
