Whether you have ever been a smoker or not, tolerating cigarette smoke used to be a part of everyday life for many people. If you are over the age of thirty, then you likely remember a time when it was ok to fill public spaces with toxic clouds. Luckily, fewer people are smoking these days, and that is a good thing, as nicotine can kill instantly in sufficient doses. High enough doses of nicotine can cause a human, or any animal, to experience involuntary muscle contractions that lead to paralysis followed by a quick death.
Any animal that possesses muscles can die from nicotine overdose. It is not uncommon for insects to die of nicotine overdose in nature, as some plants produce nicotine as a defense against hungry insect pests. Considering this, it should be obvious that the tobacco plant is well protected from most insect pests, but not all. For example, a particular moth species, the tobacco hornworm, is able to tolerate unusually high doses of nicotine that would easily kill any other insect species. When the tobacco hornworm is in its larval stage as a caterpillar, it feeds on tobacco plants, and this insect’s physiology is specialized for feeding specifically on tobacco plants. Not only can this caterpillar survive ingesting high doses of nicotine, but it can also save nicotine in order to use it for its own defense against other insect predators.
The nicotine that these caterpillars ingest can be emitted from their bodies in order to fend off, or kill, insect predators. These nicotine emissions are referred to as “chronic halitosis” by scientists who compare the emissions to bad breath.
This clever trick on the part of hornworms was discovered after scientists genetically removed nicotine producing genes from tobacco plants. Most of the hornworms that consumed these non-nicotine-containing tobacco plants were eaten by predators within a short amount of time, as they were no longer able to emit their noxious fumes as a defensive measure. The super fast wolf spider is the primary arthropod predator of these hornworms.
Do you believe that plants emit more than one type of toxic substance as a form of defense against arthropod pests?