Hornworm Uses Tobacco To Avoid Predators

Hornworm Caterpillar

Tobacco in any form is hazardous. Recently a positive aspect of tobacco has been discovered, although not for humans. Team of researchers from the Max-Planck-Institute for Chemical Ecology has found hornworm caterpillars (Manduca sexta) using tobacco as defense mechanism. These caterpillars thrive on tobacco plants and thus absorb large amount of nicotine. When in danger hornworm caterpillars expel (halitosis) some amount of nicotine toxin reserved in its blood to avert its approaching enemies such as wolf spiders and other predators. 

Other insects are also known to use plant toxin in defense mechanism. Certain bugs use toxin puke to drive off its predator. Another caterpillar known as eastern tent ejects hydrogen cyanide and benzaldehyde consumed from his or her cyanogenic (i.e. cyanide-containing) plants when invaded by ants. However the use of toxic breath as a citadel is uncommon.

Nicotine is harmful to humans as well as for other creatures and so researchers were surprised to see how does nicotine does not have any adverse effect on tiny caterpillars. The caterpillar spend their entire day feeding on the tobacco plant and in the process consume nicotine equivalent to that present in one cigarette. Therefore believed that the hornworm caterpillar have some kind of mechanism neutralizing the toxic effect of nicotine.

Researchers for the study used genetically altered tobacco plants with low nicotine content in the area where these caterpillars lived. Surprisingly they found that the caterpillars lost their ability to ward off wolf spiders. They studied the hornworms use of CYP6B46, a protein well known to negate toxin plants in other creatures. The caterpillar exercises the protein in a particular way that influences the predators as well as the hornworms. The caterpillars do not completely evade the toxic effect rather uses some of the nicotine by procuring it from the bloodstream and then releasing it out from the opening known as spiracles to keep its enemies at bay. Unfortunately, this defense method does not has any effect on other predators such as bugs or antlions.

The learning from the study can be utilized in creating genetically altered plants more suited to tolerate such predators. And with further research the scientist may be able to keep useful bugs alive and making the unwanted bugs more alluring for predators and thus reducing the use of chemicals.

Source: Discovery News

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