A giant centipede’s many wriggling legs might be creepy. But the pair of legs not used for walking may be the most frightening.
Over 430 million years ago, the two legs nearest the mouth evolved into sharp pincers that contain venom glands. Within those glands are microscopic factories capable of manufacturing multiple toxic compounds.
Arthropods, just like spiders, giant centipedes use these tools to hunt prey — everything from crickets to snakes. But they also make for a juicy snack for other animals, forcing them to defend themselves with the same poisonous pincers.
In a paper published this month in the journal Nature Ecology & Evolution, scientists revealed that the redheaded centipede — a species of giant centipede roughly the length of a ballpoint pen — is a toxic mixologist, capable of tailoring its venom recipe depending on whether it’s attacking prey or defending itself. The toxins reserved for the centipedes’ predators appear designed to cause pain, the researchers found.
The findings also may hint that venoms produced by other animals might be more complex than were previously understood.
To collect venom, scientists most often zap an animal with a nonlethal amount of electricity. The pulses contract the animals’ muscles, which squeezes out the venom. This technique is believed to release venom with all its toxic molecules, said Vanessa Schendel, who is a venom biologist at the University of Queensland in Australia and an author of the new study.
Dr. Schendel gathered centipede venom using electricity, but she also tried something bolder: She picked up centipedes to mimic a predatory attack and collected the venom that they secreted.
When the team analyzed the toxins in venom collected using the two methods, they found surprising molecular differences. This meant that neither venom held all the toxins the centipedes produce.
“I thought there was something wrong,” Dr. Schendel said. But the pattern held across multiple experiments.
Her curiosity was piqued further when she tested the two venom concoctions on crickets and on commercially available mammalian neurons used in lab settings. Both venoms caused paralysis in crickets. But only the defensive venom led to pain responses in the neurons.
She and her colleagues also wanted to run the experiment on the venom that centipedes inject into prey, which required dissecting venom glands and identifying the toxins inside. That allowed them to compare which toxins were released before an attack, as well as those secreted during an act of defense or predation.
Their chemical analysis revealed that “this species uses different venom cocktails for predation and defense,” Dr. Schendel said.
This led the researchers to look microscopically at the centipede’s venom gland. The images revealed that each of the 20,000 toxin factories in the species’ venom glands houses two types of secretory cells.
One cell type releases its contents when squeezed by surrounding muscles, while the other responds to chemical signals from hormones and neurotransmitters like serotonin. The two-part system allows the centipede to selectively activate different combinations of toxins, producing precisely tailored venom cocktails.
Dr. Schendel said redheaded centipedes might have evolved this method to save specific concoctions for when they need them because the molecules in venom regenerate slowly. “During that time period, the venomous animal is more vulnerable,” she said. The scientists speculated that the defensive venom is more painful than the hunting venom to help scare away predators.
Michel Dugon, who is a zoologist at the University of Galway in Ireland and was not involved in the study, has long been suspicious that venomous arthropods could change their toxic cocktails. He called the researchers’ efforts “elegant,” adding that this study revealed the most detailed description of any venom system.
Although it’s still unknown if other animals have the same ability, Dr. Dugon said the conventional ways of studying venom might be hiding many medically applicable molecules from view, such as targets for antivenom or options for new drugs.
“That is really cool,” he said, “but also scary because it means that a lot of work we’ve done for the past 20 years is not complete.”
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