|Batrachotoxins, or frog toxins that are found in
the genus phyllobates of poison dart frogs, have
been identified in the diet of the frogs rather
than being self-synthesized. I was wondering since
the discovery that beetles from the family
merylidae were known to contain the batrachotoxin
ingredients, how did the beetles obtain the
necessary parts for batrachotoxin synthesis, since
these beetles cannot make the toxin themselves?
Has a plant source been identified that makes the
alkaloids for beetles to consume, and if so, how
do plants make batrachotoxin in the first place?
I found a paper published in 2004 by John
Dumbacher that says essentially what you've
described: that the poisonous secretions in
poison-dart frogs and toxic birds may arise from
eating melyrid beetles containing batrachotoxin
alkaloids. They say that they don't believe that
the beetles contain the necessary molecular
machinery to produce the toxin from scratch, but
that parts may come from plants. Specifically,
beetles don't synthesize steroid skeletons (part
of the structure of batrachotoxin), but these are
found in plants. When the beetles eat the plants,
these steroid skeletons can be modified by the
beetle or a symbiotic organism inside the beetle
to produce the batrachotoxin.
The paper acknowledged that the matter was
still under investigation. I looked around for a
while, but didn't find any newer papers with more
details, so the question may still be an open one
with many details yet to be explored. The leading
hypothesis, however, appears to be that the final
structure of the toxin is produced inside of the
beetles, but using starting materials from plants
eaten by the beetles.
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