Alert reader Michael called my attention to an article and video about the world’s leggiest animal. The species is a millipede found in Northern California, lllacme plenipes, and was first described in 1926, and has up to 750 legs. It’s also sexually dimorphic, so males are smaller and have fewer legs.
Over the course of three trips to the California Floristic Province, scientists found four male specimens and three females, which they report in the June 8  issue of the journal Nature.
The females, as in turned out, were not only longer at about 1.3 inches, but also had up to 666 legs. The males averaged 0.6 inches in length and walked on no more than 402 legs.
The males and females probably start out at the same size. Females grow larger and develop more body segments, explained the report’s co-author Paul Marek of East Carolina University. “They are also wider.”
That report gave a record of 666 legs, suggesting that this animal was the work of Satan.
Here it is:
But a LiveScience piece this November 14, reporting a new study by Paul Marek et al. in ZooKeys (reference below), shows that reanalysis of more individuals of this species has shattered the leg record—up to a whopping 750! And there are other oddities:
“It basically looks like a thread,” lead study author Paul Marek, a postdoctoral entomologist at the University of Arizona, told LiveScience. “It has an uninteresting outward appearance, but when we looked at it with SEM and compound microscopes, we found a huge, amazingly complex anatomy.” (SEM stands for “scanning electron microscopy.”)
A rudimentary fused mouth with no known function is among the oddities, as are hairs on its back that produce a silklike product. “There was this huge amount of neat detail that we’re just scraping the surface of,” Marek said. [See Photos of the Bizarre Millipede]
A rudimentary mouth with no function? (See below for a photo). How does it eat?
I’ll confess that I haven’t read the 35-page paper, as I’m off to the UK today, but I’ve scanned it and present this animal for your delectation.
Here’s a scanning electron microscope (SEM) photo of the legs of a male from the paper:
Why so many legs? The authors offer an adaptive hypothesis in the abstract:
Based on functional morphology of related species, the extreme number of legs is hypothesized to be associated with a life spent burrowing deep underground, and clinging to the surface of sandstone boulders.
Well, that’s pure speculation, and do they really need that many legs to live in such a niche? Wouldn’t 700 do? Other constraints may have operated here: selection could have been for a thin creature of great length, and the number of legs could simply be a byproduct of genes making the animal longer.
Its head and antennae (see more photos here, or in the paper):
And finally, a video of the beast. Note how large its antennae are relative to its head (shown also in the photo above), and how it’s constantly using them to feel its way about, as expected from a fossorial (underground) animal:
Marek, P. , W. Shear, and J. Bond. 2012. A redescription of the leggiest animal, the millipedeIllacme plenipes, with notes on its natural history and biogeography (Diplopoda, Siphonophorida, Siphonorhinide). ZooKeys 241:77-112.