Scientists Have Identified the First ‘True’ Millipede

Millipedes have been deceiving you. Though milli means thousand, and pede means foot, no millipede had ever actually been seen with 1,000 legs. The name was used figuratively, not literally. In practice, it meant,  “Whoa, that’s a lot of legs.” 

Aristotle wrote in On the Parts of Animals that millipedes have “the greatest number of feet.” In Dutch, miljoenpoten means a million feet, and it’s centipedes that are called duizendpoten, or a thousand feet. 

“I am sure the name was coined when no one really counted the legs of a millipede, they saw it was several hundred,” said Thomas Wesener, a curator at the Zoological Research Museum Alexander Koenig, and head of the Myriapoda section, which covers a grouping of arthropods that includes millipedes. 

The most legs any known millipede possessed was 750—until now. A new millipede species has been discovered, called Eumillipes persephone, with a record-shattering 1,306 legs. The finding was published today in Nature Scientific Reports. 

By being so leggy, Eumillipes persephone has earned the title of the first “true” millipede. The name the scientists who discovered it picked reflects this: Eumillipes combines the Greek eu-, for “true”; the Latin mille, for “thousand”; and Latin pes, or “foot.” Persephone is a reference to the Greek mythological goddess of the underworld—the new millipede was found over 196 feet below ground in Western Australia, in a hole originally drilled for mineral exploration.

“There is probably no more spectacular discovery to be made than finally a millipede with 1,000 legs,” Wesener said, who was not involved in the new work. 

Eumillipes persephone’s other claims to fame? It has no eyes, a cone-shaped head with enormous antennae, a beak for eating, and is incredibly long and skinny: Its body is made up of 330 segments, and is 95 millimeters long.

“We always hypothesized that there would be a ‘true’ millipede discovered some day,” said Jackson Means, a myriapodologist at the Virginia Museum of Natural History. But the discovery of one with over 1,300 legs, almost double the previous leg count? “That was pretty astonishing.” 

Eumillipes persephone was first spotted last year, when Bruno Buzatto, an honorary lecturer at Macquarie University in Australia, was called over to look at an unusually long millipede extracted from leaf litter used in underground traps. “I quickly realized that the longest specimen in front of my eyes had to have at least 800 [legs],” Buzatto said.

It reminded him of a 2006 paper describing the previously leggiest millipede—a species called Illacme plenipes from California. He reached out to Paul Marek, one of the authors, and an entomologist at Virginia Tech. Intrigued, Marek and Buzatto agreed to send the millipede by mail from Australia to Virginia.

After its long journey, Marek looked at the millipede under his research microscope, and said it was clear it was a different order than the Californian millipede afterall, and a brand new species. The Californian millipede belonged to the order Siphonophorida, while the Australian millipede belongs to the order Polyzoniida. 

Previous Polyzoniidans haven’t been found so deep underground before, and most from Australia look very different than Eumillipes persephone—they have 400 legs at most, eyes, and flat and wide bodies. 

Then, Marek set out to count the legs by counting the millipede’s body segments. He used Adobe Illustrator to mark the rings he had already counted, so he wouldn’t count one twice. It wasn’t a tedious task for him: “I did that pretty excitedly,” he said. 

Rather than being closely related, Eumillipes persephone’s similar appearance to the Californian millipede is explained through convergent evolution, Marek explained, when traits evolve more than once in separate species. Because both millipedes live underground, having a lot of legs on a long, skinny body is likely adaptive in that environment: legs allow the animal to push themselves through the soil. 

“This subterranean existence is evolutionarily shaping the shape of the body,” Marek said, a process that takes hundreds of millions of years. 

Millipedes don’t hatch with this bounty of legs, they add them to their body over time— Eumillipes persephone hatches with only eight legs. The group of millipedes that Eumillipes persephone belongs to can add segments and legs to their bodies throughout their entire life, not just up to sexual maturity. (Other millipedes do stop adding legs at an earlier point in their lifespan.) 

While the discovery is exciting on its own (and renders the name “millipede” more accurate), it also reveals how extensive the gaps in our knowledge of millipedes are. There are over 12,000 described millipede species, but the number of known millipedes is dwarfed by millipede mysteries: There are an estimated 80,000 to 100,000 undescribed species. 

The millipedes we know come in all sorts of shapes and sizes. There are tiny, fuzzy millipedes that live under bark, pink or orange frond-shaped millipedes, and flat-backed millipedes that roam glow blue under a UV blacklight, said Xavier Zahnle, a graduate student in Jason Bond's entomology and nematology lab at University of California, Davis.

Millipedes and centipedes can be referred to interchangeably in conversation, but they are very different organisms. Centipedes are carnivores, and they capture prey and inject them with venom—this is why centipedes belong to the class Chilopoda, which means “lips legs.” The name comes from the “enlarged venomous fangs that evolved from the first pair of legs just behind the head,” Zahnle said.

“Centipedes are fast-running predators who kill their prey with poison claws,” said Henrik Enghoff, a curator of Myriapoda at the Natural History Museum of Denmark.” Millipedes are docile detritivores who chew dead leaves.”

Millipedes have been around for about 420 million years. They were the first known animal to breathe atmospheric oxygen, based on fossil evidence. Some extinct species were over 6 feet long and 1 foot wide. 

“As terrestrialization of this planet was occurring, the things that set the stage were primitive plants, which were then decaying, and millipedes were there to feed on them,” Marek said. 

Because they are slow moving and can’t fly or swim, millipedes can also grant a window into the biogeographical history of an area. Millipede groups on the island of Madagascar are related to species now living in India; this is because they are both survivors from when India and Madagascar formed an island, long before India drifted north to attach itself to Asia.

Despite being docile, there is also evidence that millipedes were one of the first animals to produce chemical defenses, and the first to have external genitalia, Means said. One of those defenses is cyanide. One species called cherry millipedes releases hydrogen cyanide to fend off predators—a chemical that can smell like cherries (and sometimes almonds). 

In at least one species, father millipedes exhibit a behavior called “parental care” which is rare in nature: He will curl his body around his eggs to protect them until they hatch. “I’ve seen neat examples of the father walking around with a clutch of eggs in his middle legs and walking with the front and the back legs kind of like a little like hunched over, like an inchworm,” Marek said.

These are alluring reasons to keep studying millipede diversity, but it’s also critical we learn about them for their contributions to the health of the ecosystems that they live in. 

By eating decaying vegetation, and sometimes fungi, that contain nutrients like carbon and nitrogen and simple sugars, they break down organic material into smaller bits so it can cycle through the environment. This essential process couldn’t happen without decomposers, and since a lot of native earthworms in the United States have gone extinct as a result of introduced earthworms, millipedes are shouldering the weight of this task. 

“It’s not something that we celebrate as much as we do with pollinators that are out there in front of us and pollinating our tomatoes,” Marek said. “[Millipedes] are like the little garbage men of the ecosystem that are doing the behind-the-scenes heavy lifting for us to have healthy ecosystems.”

It can be a race against extinction to describe a millipede species from a specific area before it is gone. There was a rare millipede Wesener and his colleagues described from Brazil, in caves once protected by Brazilian law, but the law changed so that only caves with unique species were protected—they had to find the millipede before the cave was destroyed by the iron ore mining operation. 

They were successful, and rewarded with a “sunnting” millipede. “It has a reduced exoskeleton because there are no predators in the cave, so it looks like it is made of glass, completely see through,” Wesener said. “This was the first time we could study some internal organs of this millipede group.”

Marek doesn’t want the tens of thousands of other millipedes to go extinct before we get a chance to learn about them. “The 80,000 undescribed millipedes are basically anonymous biodiversity,” Marek said. “We want to avoid anonymous extinction where a species goes extinct without us knowing about it.” 

For Eumillipes persephone, that’s luckily not the case. “It was only many weeks later, after the animals were sent to Paul, and he meticulously counted the legs of the longest individual, that we realized we had the first true millipede in hands, with well over 1,000 legs,” Buzatto said. “I felt extremely lucky to have come across such an amazing finding.”

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