For the first time science has found a true millipede, one with over a thousand legs, and of course it’s in remote Australia. In fact, it isn’t much like most of the other species of millipedes known and loved around the world, being subterranean. This new species was found during drilling for minerals in Australia’s Eastern Goldfields region.
The newly described arthropod has up to 1,306 legs, the most of any animal in the world, the people who discovered the thing 60 meters (197 feet) underground revealed Thursday in the journal Scientific Reports. And no, it isn’t a fossil of an extinct animal, it’s alive and kicking. And the biggest one was a girl.
What, never before has a millipede had a thousand feet or more? Not even close. Until now the name millipede has been a misnomer, with the best-equipped creature sporting a mere 750 legs.
The researchers weren’t shocked that the biggest was a lady. “Females are larger than the males with more segments and legs,” lead author Paul E. Marek of Virginia Tech told Haaretz. Females are larger in most arthropods because they evolved to be spacious to hold legs. Among the specimens the scientists caught, the females had 998 and 1,306 legs and the males 778 and 818.
The newly discovered species’ exalted status as a true millipede is reflected in its name: Eumillipes persephone. Yes, that derives from the Greek for foot, eu, the Latin for thousand, mille, and the Latin for foot, pes, the researchers explain in their paper.
One might think that with so many legs, the persephone would be gargantuan, but the longest one of the eight caught so far was a bit under 3.7 inches long, almost 96 millimeters.
Blind queen of the underworld
This longest millipede the team caught had 330 segments, from which her 1,306 legs protrude. And then there’s her head, on which the persephones have no eyes, having adapted to the lightless underground life. Not that millipedes that do have eyes see well.
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“The millipede order with the greatest number of species, the Polydesmida with 5,000 species, all lack eyes,” Marek observes, and they've been eyeless for the past 200 million years.
The persephones’ little legs are short compared with other millipedes, and their heads are cone-shaped with antennae and a beak with which they apparently sup on fungi.
Millipedes as a rule eat decaying plant matter (in contrast to their carnivorous cousin the centipede), but deep underground, the options are more limited. Either way, the researchers caught their persephones using traps baited with delicious rotting vegetation, they write.
“This underground habitat, as in caves, is likely limited in food availability, so odors emanating from decaying vegetation are likely very appealing,” Marek says. If given their druthers they would probably choose the lovely aromatic decaying plants rather than fungus.
Millipedes and centipedes – the aptly named myriapoda – basically have nothing but a head and a segmented body, and some hatch from the egg with all their segments while others add more over time. So you have to wonder if the 330-segmented specimen was elderly.
The researchers politely didn’t ask the lady how old she was, but they agree she might be pretty old. “Millipedes in the group Colobognatha have euanamorphic development, meaning that they hatch from the egg with eight legs and as they develop add four-legged segments continuously even after adulthood,” Marek says. “The 330-ringed female is older than the ones with fewer rings and may be up to a decade old.”
The persephones’ tiny little legs are underneath their vermiform bodies. They look quite unlike African millipedes, whose legs are visible without turning them over and who have eyes. The African type is dark, even blackish, while this new Australian cousin has no pigment.
Here’s a video of how millipedes move with all those legs and why they make great pets, as far as invertebrates go, in the opinion of this YouTuber. Indeed, Clem the clam or Fifi the fruit fly would probably be less diverting.
The strange characteristics of this new millipede – extremely long and slim, everything being relative – may be an adaptation to its deep-soil lifestyle by lengthening the digestive tract to extract the maximum nutrition from its fungus dinner. One wonders if there’s any parallel with deep-earth bacteria that may live for thousands, hundreds of thousands and apparently millions of years basically because their metabolism is barely ticking over.
Asked if the persephones might be a sort of arthropodian parallel (albeit not a good one) to these barely-alive bacteria, Marek agrees that they too probably exhibit a slow metabolism and respiratory rate. “It may be very similar to the cave olm [a salamander] that was not observed to have moved in seven years,” he adds.
It’s all in the ganglia
The persephone is distantly related to a very far-off animal, the previous record holder for having the most legs, the Californian species Illacme plenipes. That’s the one that has to up 750 legs and again, the specimen with the most legs was a female. Illacme inhabits the northwestern foothills of the Gabilan Range in San Benito County, California, and seems to be very rare.
It too is eyeless, colorless, beaked and lives underground – or under a rock, which is where some of the live ones were found.
The authors suspect the two millipedes’ similarity in having long thin whippy bodies with tiny legs underneath has to do with their method of underground locomotion, finding gaps in the soil through which they slip on their presumable forays for fungal foodstuffs and friends. They can move along eight fronts at once! It’s like they’re walking through a world of small crevices, Marek says. But we don’t know if they actually move much or hardly at all.
They can move along eight fronts? How do they coordinate hundreds of legs let alone 1,306 of them with their rather low nervous system? “Millipedes like many arthropods have a ventral nerve cord. The ventral nerve cord is a linear nervous system with ganglia on each segment,” Marek explains; ganglia are essentially tiny distributed brains.
“What’s interesting about millipedes is that they evolved from ancestors with one pair of legs per segment that fused into ‘diplosegments’ in millipedes. These diplosegments have two ganglia. Ganglia process messages from the brain and move the muscles controlling the legs. Leg movement is a process of simple movements repeated along the length of the millipede. The adjoining legs are out of sync and impart the metachronal gait that we see in them.” Got it.
The two millipedes, the Californian and now the Australian, are members of the Siphonophorida order, which has been called “a taxonomist’s nightmare” – not because of how they look; that’s our nightmare. No, taxonomists were bedeviled by the embarrassing diversity of characteristics, which led to mistakes.
“Published descriptions have in the past used characters that were found to vary between individuals of the same species, or even within the same individual,” an article in the journal Soil Organisms explained. Now we know.