[pcplantdb] Example of inputs and outputs changing midstream/on the fly for an insect
Lawrence F. London, Jr.
lfl at intrex.net
Tue Aug 2 05:16:45 EDT 2005
BBC NEWS | Science/Nature | Grubs fight parasites with food
Last Updated: Monday, 1 August 2005, 09:55 GMT 10:55 UK
Grubs fight parasites with food
Caterpillar, Michael Singer
The caterpillars develop a fondness for certain plants to fight a
Tiger moth caterpillars have been seen medicating themselves to treat a
nasty influx of parasites.
Scientists found the caterpillars' sense of taste actually changed when
they became infected with parasites.
Instead of avoiding certain alkaloid plants, the caterpillars actually
developed a fondness for them.
This change in diet helps to beat the creatures' parasite infection, the
researchers report in Nature.
The finding is slightly unusual because often when animals change their
behaviour following a parasitic infection, it is to the invaders' benefit.
"It is a new and surprising kind of interaction between organisms," said
Elizabeth Bernays, of the University of Arizona, US.
"When parasites change the behaviour of their hosts, it's usually to
their own advantage."
Race to live
Caterpillars of the tiger moths Grammia geneura and Estigmene acrea ,
which live in the grasslands of southern Arizona, US, are susceptible to
a range of insect parasites.
The parasitic flies lay eggs on the surface of the caterpillars' skin
which, on hatching, bore into the larvae's flesh.
They can survive because they find the protective plants more tasty
Elizabeth Bernays, University of Arizona
It is here that the struggle for life between host and parasite really
The parasite's objective is to feast on the generous supply of live
tissue, before it pupates and bursts out of the dead caterpillar.
If the caterpillar is to survive such an onslaught, it must develop an
effective defence strategy.
Instead of eating a wide range of plants, which the tiger moth larva
usually does, the caterpillar becomes much more specific: it homes in on
plants that are particularly toxic to its parasites.
These plants, such as woolly plantain, produce chemicals known as
pyrrolizidine alkaloids and iridoid glycosides.
Not only do these chemicals wash through the caterpillar's body, making
it an unattractive meal, they also collect in its skin, deterring future
Dr Bernays and her colleagues found that, when a caterpillar acquires a
parasite infection, its taste cells react differently to the chemicals
These cells become more responsive to the protective chemicals and less
sensitive to other chemicals, which are usually distasteful to the
Just how this change occurs in the caterpillars is not known yet.
"It's still a mystery how they do it," Dr Bernays said. "But the result
for the caterpillars is the same: they can survive because they find the
protective plants more tasty."
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