Contrary to dogma that defensive venoms are simple in composition, mottled cup moth caterpillars (Doratifera vulnerans) produce a very complex venom containing 151 toxins spanning 59 families, most of which are peptides.

The mottled cup moth caterpillar (Doratifera vulnerans). Image credit: Jiayi Jin.

The mottled cup moth caterpillar (Doratifera vulnerans). Image credit: Jiayi Jin.

Doratifera vulnerans is a common culprit of caterpillar envenomations in Australia.

The binomial name of this species etymologically means ‘bearer of painful gifts.’

Doratifera vulnerans caterpillars are endowed with venomous spines.

Like all members of the genus Doratifera, the groups of large venom spines are retracted at rest and everted when the animal is disturbed, a behavior that is possibly an adaptation to prevent premature discharge of venom from the spines.

“Many caterpillars produce pain-inducing venoms and have evolved biological defenses such as irritative hairs, toxins that render them poisonous to eat, spots that mimic snake eyes or spines that inject liquid venoms,” said Dr. Andrew Walker, a researcher in the Institute for Molecular Bioscience at the University of Queensland.

“Previously researchers had no idea what was in the venom or how they induce pain.”

To provide a holistic picture of the venom system of Doratifera vulnerans, Dr. Walker used various imaging technologies, transcriptomic, proteomic and functional techniques.

The researchers found the caterpillar has venom toxins with a molecular structure similar to those produced by spiders, wasps, bees and ants.

They also unlocked a source of bioactive peptides that may have uses in medicine, biotechnology or as scientific tools.

“We found that the venom is mostly peptides and shows stunning complexity, containing 151 different protein-based toxins from 59 different families,” Dr. Walker said.

The scientists then synthesized 13 of the peptide toxins and used them to show the unique evolutionary trajectory the caterpillar followed to produce pain-inducing venom.

“We now know the amino acid sequences, or the blueprints, of each protein-based toxin. This will enable us to make the toxins and test them in diverse ways,” Dr. Walker said.

Some peptides showed very high potency, with potential to efficiently kill nematode parasites that are harmful to livestock, as well as disease-causing pathogens.

“Our research unlocks a new source of bioactive peptides that may have use in medicine, through an ability to influence biological processes and promote good health,” Dr. Walker said.

“First, we need to work out what the individual toxins do, to inform us about how they might be used.”

The team’s results were published in the Proceedings of the National Academy of Sciences.

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Andrew A. Walker et al. 2021. Production, composition, and mode of action of the painful defensive venom produced by a limacodid caterpillar, Doratifera vulnerans. PNAS 118 (18): e2023815118; doi: 10.1073/pnas.2023815118

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