The leggiest animal in the world, the millipede lllacme plenipes, was re-discovered several years ago in California by Paul Marek. Now, Marek and his colleagues provide further details of the surprisingly complex anatomy of this diminutive creature and its extreme rarity, limited to a handful of spots just south of San Francisco. More details about the species and its biology can be read in an article that was recently published in the open access journal ZooKeys.
Millipedes have the most legs of any animal group. From their ancestors with just one pair of legs per body segment, millipedes evolved two pairs (four total) through segmental fusion. This coalescence of segments happened deep in the evolutionary history of millipedes, more than 400 million years ago. Four legs provide more thrust on a per segment basis, which benefits millipedes to help them burrow underground--e.g., to escape predators or access new resources. Those individuals with a coalescence of segments and hence a better burrowing ability, were able to persist in this early primordial ecosystem.
The most noticeable thing about millipedes are their number of legs, which lined up along their bodysides step in synchronous "metachronal waves". The acme of legginess in millipedes, and all animals for that matter, is the Californian species Illacme plenipes (literally meaning "in highest fulfillment of feet"). The females have up to an astounding 750 legs, outclassing the males who only have a maximum leg count of 562. The proliferation of legs may be an adaptation for its lifestyle spent burrowing underground or (based on the presence of features like legs with bifurcate claws and other traits known to be associated with rock-climbing in millipedes) enable it to cling tightly to the sandstone boulders found exclusively associated with the species in its habitat
Not only is this species the leggiest animal known on the planet, it also has surprising anatomical features: body hairs that produce silk, a jagged and scaly translucent exoskeleton, and comparatively massive (given its diminutive size) antennae that are used to feel its way through the dark because it lacks eyes. Its mouth, unlike other millipedes that chew with developed grinding mouthparts, is rudimentary and fused into structures that are probably used for piercing and sucking plant or fungal tissues.
This rare and ancient-looking creature's home is California, on the outskirts of Silicon Valley. The species is exceedingly scarce and limited to just a single tiny area near San Juan Bautista, just east of the San Andreas Fault. Based on the known environmental conditions where it lives, the species' probable distribution elsewhere in California was inferred. Yet still restricted to a small geographical range, the analysis indicated other areas of suitability limited to the terrestrial areas on the edge of Monterey Bay eastward to San Juan Bautista and throughout the Salinas Valley. What's unique about this area, and seems to be correlated with the model's area of highest suitability, is the thick layer of fog that accumulates in the area--like soup in a deep bowl. The fog and the species' unique set of features in its habitat (oak forests, sandstone boulders, and fine sandy soil) make this area a special place and certainly deserving of attention as the home of this rare and superlative beast.
Marek PE, Shear WA, Bond JE (2012) A redescription of the leggiest animal, the millipede Illacme plenipes, with notes on its natural history and biogeography (Diplopoda, Siphonophorida, Siphonorhinidae). ZooKeys 241: 77. doi: 10.3897/zookeys.241.3831
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In the article on the discovery of dinosaurs (They’re back, Review, 6 June) you state: “In Sussex, a local doctor uncovered fragmentary remains of what appeared to be two more species of colossal extinct land reptiles.” You grossly underplay the contribution of Lewes-born Gideon Mantell, geologist and palaeontologist, author and diarist, friend to princes and international scholars as well as local doctor. Mantell not only discovered (aided by his wife) the first remains of the iguanodon in 1824 but named it – as it resembled the tooth of an iguana. This was the first known land dinosaur, Mary Anning having identified the first sea-living dinosaur.Mantell went on to put together more pieces of the jigsaw with extra fossil discoveries. In contrast to Richard Owen, whose models form the basis for the Crystal Palace dinosaurs, Mantell stated correctly that iguanodon would have walked on their back legs, using their forearms to fight or gather food. He did, however, attribute the thumb spike to a nose horn though later corrected this assumption. The Natural History Museum has a display on Gideon and his wife Mary’s contribution as well as the large “Mantell-piece” of Iguanodon fossils that he had on show in his museum in Brighton. He sold it, along with many more priceless items, to the British Museum in 1838. Gideon Mantell’s reputation deserves better than your throwaway remark. Debby MatthewsLewes, East Sussex Continue reading...