Beetle juice studies

So how do insects make those smelly, sticky, stinging or otherwise noxious chemicals with which they defend themselves?

It varies from species to species, German biochemist Wilhelm Boland explained in a Smithsonian Tropical Research Institute lecture. Moreover, it seems that some of the more advanced insects use simpler and thus more adaptable methods.

Dr. Boland, a researcher at the Max Planck Institute in Jena, Germany, has been spending the last several years studying leaf beetles and how they separate and use plant chemicals for their own defenses. In the course of this he and his colleagues have noticed that the same species in different life phases --- eggs, larvae, pupae and adults --- may have different chemical defenses. For his comparative study among three different beetle species, he concentrated on the larvae, starting by annoying them with tweezers until they emitted chemicals to analyze.

Through a whole series of tests and experiments --- for example by coating leaves that the beetles like to eat with the defensive chemicals and seeing if the substances are directly absorbed --- Boland has learned that while the simpler insects tend to synthesize their chemical defenses in their bodies, generally relying on one sort of plant food to do so, the more advanced beetles are more likely to separate, store and use plant chemicals more directly, and moreover can do so from several different plant food sources. That makes them more adaptable to changes in their environments.

More mysterious is how the chemicals get from the insects’ guts to the glands in which they are modified by catalysts, and then into the reservoirs in which the ultimate defensive goo is held for use against nature’s predators or those obnoxious scientists with their tweezers. It seems that the beetles’ guts are impermeable by plant toxins stored within. “There must be transport proteins” to combine with these substances and render them into a form that can get out of the guts and into the glands and reservoirs, and then other proteins to separate the plant substances back out, Boland said.

And that set off another chain of experiments, in which it was established that whatever these transport proteins are, they very specifically recognize the plant chemicals that they want to transport. With the more advanced insects that can use several plant chemicals, he believes that there are several different proteins employed.

However, the search is still on to identify these transport proteins, which, though theoretically shown to exist, have yet to be isolated.

science

Beetles that use plant substances
to make a big stink

science

Beetles that use plant substances to make a big stink

Beetles that use plant substances
to make a big stink