Worldwide, an estimated 100,000 animal species produce toxins. Some serve to protect against predators, others to hunt prey. What many poisons have in common is that they can have the opposite effect in small doses: Important antihypertensives, anticoagulants and pain killers are based on animal toxins, and a toxin of the bacterium Bacillus thuringiensis is making waves as a biological insecticide. Unlike snakes or spiders, little is known about the toxins of predatory flies. Researchers at the Justus Liebig University in Giessen and the LOEWE Centre have now investigated those of a species of robber fly native to Hesse.

So far unknown toxins discovered

Like other predatory insects, the robber fly uses toxins to hunt its prey. Many of these toxins were previously unknown, as evolutionary biologists report in the scientific journal "GigaScience". Genetic analyses confirmed that a large proportion of the toxins developed only in predatory flies and not in other species. "By comparing it with the genomes of related fly species and other insects, we were able to show that, in addition to toxin families known from other poisonous animals, toxin-encoding genes in predatory flies were formed in the course of evolution, which apparently only occur in this group," sums up Stephan Drukewitz of the Fraunhofer Institute for Molecular Biology and Applied Ecology, which is involved in the LOEWE Center.

Toxins with species-specific effects

Over millions of years, evolution has thus tailored the effectiveness of the robber fly’s poison cocktail to its prey insects. It would therefore be possible to use some of the toxins in agriculture as bioinsecticides, because the toxins often have a very specific effect against only one insect species. "In times of an unprecedented decline in insects, the sustainable use of insecticides is of utmost importance," said Björn von Reumont, head of research.

Protein with neurotoxic effects

The researchers are now working on clarifying the mechanisms of action of the robber fly toxins. "The activity of most predatory fly-specific toxins is still unknown," reports von Reumont. "We are currently testing these toxins in the laboratory of our animal toxins research group in order to determine their potential applications. However, the team has already identified an initial toxin with medical potential: Asilidin1, a short protein with neurotoxic effects."

"Our results show how important it is to better investigate not only snakes, spiders and scorpions, but also lesser known toxic animal groups," Drukewitz emphasizes. The study is the largest comparative genome analysis that uses predatory flies as an example to investigate the evolutionary processes underlying the development of the various toxin genes.

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