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| Michael Singer,
assistant professor of biology, discovered that the wolly bear caterpillar,
Grammia geneura, ingests medicinal plants when sick. |
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| Posted 08.17.05 |
When Ill, These Caterpillars Acquire a Taste for Medicinal Plants
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When tiger moth
caterpillars get a bug, they do what a lot of us do - ingest some medicine
and hope it provides a cure.
These findings by co-investigators Michael Singer, assistant professor of
biology, and Elizabeth Bernays, regents professor emerita of entomology at
the University of Arizona, appear in the July 27 issue of Nature.
During a study of the caterpillars of two types of tiger moths, known as
Grammia geneura and Estigmene acrea, Singer and Bernays observed
that when the caterpillars were besieged by potentially deadly parasites,
they underwent a chemical change that affected their taste sensing cells.
The result: the infected caterpillars suddenly acquired a taste for plants
that contained compounds - iridoid glycosides and pyrrolizidine alkaloids.
When plants containing these compounds are ingested by the caterpillars the
parasites die, often before they could inflict mortal harm on the
caterpillars from within.
Singer and Bernays noted that the taste for these medicinal components was
heightened in the infected caterpillars while remaining unchanged in
uninfected caterpillars.
"In essence, contracting the parasites actually triggers a chemical reaction
inside the caterpillars that makes them more disposed to eating the very
plants that may help them get rid of these deadly organisms," Singer says.
"The parasites are actually setting in motion a process that may lead to
their own demise, provided the caterpillars can get to the right type of
plants in time."
Singer adds that this type of chemical "taste change" that gravitates the
caterpillars toward medicinal foods has not been observed in other
caterpillars, but is likely to occur as in other animals that are known to
self-medicate, including some primates.
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| By David Pesci, director of
Media Relations |
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