Chemistry behind bombardier beetle's extraordinary firepower

Date:
June 16, 2020
Source:
Stevens Institute of Technology
Summary:
Researchers show how how the bombardier beetle concocts its deadly
explosives and in the process, learn how evolution gave rise to
the beetle's remarkable firepower.



FULL STORY ==========================================================================
If you want to see one of the wonders of the natural world, just startle
a bombardier beetle. But be careful: when the beetles are scared, they
flood an internal chamber with a complex cocktail of aromatic chemicals, triggering a cascade of chemical reactions that detonates the fluid and
sends it shooting out of the insect's spray nozzle in a machine-gun-like
pulse of toxic, scalding-hot vapor. The explosive, high-pressure burst
of noxious chemicals doesn't harm the beetle, but it stains and irritates
human skin -- and can kill smaller enemies outright.


==========================================================================
The beetle's extraordinary arsenal has been held up by some as a proof of
God's existence: how on earth, creationists argue, could such a complex, multistep defense mechanism evolve by chance? Now researchers at Stevens Institute of Technology in Hoboken, N.J. show how the bombardier beetle concocts its deadly explosives and in the process, learn how evolution
gave rise to the beetle's remarkable firepower.

"We explain for the first time how these incredible beetles biosynthesize chemicals to create fuel for their explosions," said Athula Attygalle,
a research professor of chemistry and lead author of the work, which
appears today in the July 2020 issue of the Science of Nature. "It's a fascinating story that nobody has been able to tell before." To trace the workings of the beetle's internal chemistry set, Attygalle and colleagues
at University of California, Berkeley used deuterium, a rare hydrogen
isotope, to tag specially synthesized chemical blends. The team led by
Kipling Will then either injected the deuterium-labeled chemicals into
the beetles' internal fluids, or mixed them with dog food and fed them
to the beetles over a period of several days.

Attygalle's team sedated the bugs by popping them in the freezer, then
gently tugged at their legs, annoying the sleepy insects until they
launched their defensive sprays onto carefully placed filter papers. The
team also dissected some beetles, using human hairs to tie closed the
tiny ducts linking their chemical reservoirs and reaction chambers,
and sampling the raw chemicals used to generate explosions.

Using mass spectrometers, Attygalle checked the samples sent to Stevens
for deuterium-labeled products, enabling him to figure out exactly
which chemicals the beetles had incorporated into their bomb-making
kits. "People have been speculating about this for at least 50 years,
but at last we have a clear answer," Attygalle said. "It turns out that
the beetles' biochemistry is even more intricate than we'd thought." Previously, researchers had assumed that two toxic, benzene-like chemicals called benzoquinones found in the beetles' spray were metabolized from hydroquinone, a toxic chemical that in humans can cause cancer or genetic damage. The team at Stevens showed that in fact just one of the beetle's benzoquinones derived from hydroquinone, with the other springing from
a completely separate precursor: m-cresol, a toxin found in coal tar.

It's fascinating that the beetles can safely metabolize such toxic
chemicals, Attygalle said. In future studies, he hopes to follow the
beetles' chemical supply chain further upstream, to learn how the
precursors are biosynthesized from naturally available substances.

The team's findings also show that the beetles' explosives rely on
chemical pathways found in many other creepy-crawlies. Other animals
such as millipedes also use benzoquinones to discourage predators,
although they lack the bombardier's ability to detonate their chemical defenses. Evolutionarily distant creatures such as spiders and millipedes
use similar strategies, too, suggesting that multiple organisms have independently evolved ways to biosynthesize the chemicals.

That's a reminder that the bombardier beetle, though remarkable, is
part of a rich and completely natural evolutionary tapestry, Attygalle
said. "By studying the similarities and differences between beetles'
chemistry, we can see more clearly how they and other species fit
together into the evolutionary tree," he explained. "Beetles are
incredibly diverse, and they all have amazing chemical stories to tell."

========================================================================== Story Source: Materials provided by Stevens_Institute_of_Technology. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Athula B. Attygalle, Sihang Xu, Wendy Moore, Reilly McManus,
Aman Gill,
Kipling Will. Biosynthetic origin of benzoquinones in the explosive
discharge of the bombardier beetle Brachinus elongatulus. The
Science of Nature, 2020; 107 (4) DOI: 10.1007/s00114-020-01683-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200616173227.htm

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