Monday, December 30, 2013

Stinking Warning: bad breath protects them from predators - NEWS

 A four-leaf tobacco hornworm (Manduca sexta) dips his tongue into a flower. A four-leaf tobacco hornworm (Manduca sexta) dips his tongue into a flower (photo: dpa).

Tuesday 31 December 2013

The tobacco hornworm caterpillars use a substance their preferred host plant to ward off predators: nicotine. They warn the robbers by stink. Without the nerve agent, they are more often captured by spiders.

In a lab at the Max Planck Institute for Chemical Ecology in Jena, the larva eats a Tabakschwä rmers on a tobacco plant. In a lab at the Max Planck Institute for Chemical Ecology in Jena eats the larva of the tobacco hornworm on a tobacco plant (photo: dpa).

With a kind of bad breath, the caterpillars of the tobacco hornworm protect from being eaten by wolf spiders. A portion of the nicotine from the tobacco leaves gelange in the insect blood and will be exhaled through small openings in the skin, so to speak, report biologists from the Max Planck Institute for Chemical Ecology in Jena in the “Proceedings” of the U.S. Academy of Sciences (PNAS). That was a foul-smelling warning to predators that deters spiders.

caterpillars on nicotine-free tobacco plants spiders devour well, as those in which the gene has been switched off for a given enzyme digestion. As a result, the butterfly junior was hardly to no stinking warning from the researchers write.

nicotine-free tobacco plants

The team led by Ian Thomas Baldwin researched for years the caterpillars of the tobacco hornworm. The butterfly is found in North and South America and feeds mainly on tobacco plants. The researchers noticed that at night especially many caterpillars were destroyed when they sat on by genetic engineering nicotine-made tobacco plants. Wolf spiders of the species Camptocosa parallela they had eaten.

an elaborate study, the researchers have now found out why: Normally, the tobacco hornworm caterpillars eat leaves of tobacco plants containing abundant nicotine. In the cells of the midgut, a gene designated CYP6B46 is then turned on. Then a specific protein is produced, which acts as a digestive enzyme cytochrome P450 6B46


nicotine exhaled

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This protein ensures that approximately 0.65 percent of the nicotine is released from the digested midgut in the so-called hemolymph. The hemolymph is the body fluid in invertebrates that do not have a closed circulatory system. About finely branched channels of the skin, the nicotine is then as it were exhaled.

In an experiment of this seizure protection mechanism was checked again: Some caterpillars were exposed to specially prepared tobacco plants which, although containing nicotine, but made sure that the caterpillars CYP6B46 the gene is shut down. Then significantly less nicotine was transferred to the hemolymph. “That’s why come CYP6B46-disused larvae less nicotine and are easy prey for spiders,” the researchers write. 25 of 50 such larvae survived the night not – while 40 of 50 larvae survived on normal tobacco plants, the night



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