A new study has established the first-ever evolutionary history of all living millipedes, one of the planet\u2019s first land animals that pioneered its terrestrial ecosystems (as the first chemical weapon manufacturers, too).<\/p>\n
At a time when the Earth was bare, when there were no vertebrates, no trees, no leaves, no flowering plants, and no plants with seeds, millipedes were feeding on decaying mosses, decomposed slime, and primordial gunk.<\/p>\n
Though that sounds unappetizing, someone had to complete the \u201cdirty work\u201d necessary to pave the way for life. Though they perform an essential function as one of the first animals on Earth, science still hadn\u2019t fully tracked their history until now.<\/p>\n
A new, groundbreaking study published in Current Biology addressed a 100-year-old gap in millipede science surrounding two rare groups of millipedes: Siphoniulida and Siphonocryptida.<\/p>\n
Scientists knew that they existed, but without specimens for DNA analysis, they couldn\u2019t confirm where they belonged in the millipede family tree.<\/p>\n
But it was no easy feat to find them. One group spends its life underground, while the other survives in only a few known locations.<\/p>\n
Penetrating 260 million years of history<\/p>\n
Researchers traveled to Los Tuxtlas, Mexico, and Spain\u2019s Canary Islands to collect Siphoniulus neotropicus and Hirudicryptus canariensis, two millipedes whose DNA had never before been included in an evolutionary analysis.<\/p>\n
\u201cIt took 10 people over a week to find one tiny 10-millimeter adult,\u201d said Luisa “Fernanda” Vasquez-Valverde, the paper’s first author, in a press release.<\/p>\n
\u201cFinding them in the field was hard because we were just seeing this little white nematode. We didn\u2019t know for sure it was a millipede until we looked under the microscope.”<\/p>\n
After sequencing their DNA, comparing hundreds of genes across 82 millipede species, and combining those results with evidence from 29 fossils, researchers determined where the groups belonged in millipede history and when their lineages emerged.<\/p>\n
“Millipedes may have originated nearly 460 million years ago \u2014 roughly 35 million years before the oldest known millipede fossils and much earlier than previously believed,” according to the press release.<\/p>\n
Siphonocryptida turned out not to be a distinct order after all, but part of an existing lineage. Siphoniulida was finally placed among its closest relatives on the millipede evolution timeline.<\/p>\n
All in all, the analysis of the millipede species revealed that the ancient animals originated 460 million years ago, roughly 35 million years before the oldest known millipede fossils, which was \u201cthe biggest surprise\u201d to researchers \u2014<\/p>\n
\u201cJust how ancient these lineages turned out to be.\u201d<\/p>\n
The completed family tree also revealed one of the millipedes\u2019 most important adaptations: they made the first chemical weapons. And it was these defenses that helped scientists trace their origins to about 260 million years ago.<\/p>\n
Although the new study brought new insights into one of the planet\u2019s most significant animals, millipedes still hold secrets waiting to be discovered.<\/p>\n
Still more to discover<\/p>\n
Scientists have described more than 14,000 species worldwide, but experts believe that tens of thousands may still be out there undiscovered.<\/p>\n
These \u201cunheralded heroes of the ecosystem\u201d may be one of nature\u2019s most important detritivores \u2014 because they break down decaying plant material and return nutrients to ecosystems \u2014 but scientists still haven\u2019t fully penetrated this lineage, which is more ancient than the dinosaurs and paved the way on land for vertebrates.<\/p>\n
“It’s really kind of puzzling that they have such an important function in the ecosystem, and yet they’re so poorly known,” noted Paul Marek, the study\u2019s lead investigator and associate professor in the College of Agriculture and Life Sciences\u2019 Department of Entomology.<\/p>\n
\u201cMillipedes<\/a> beat vertebrates onto land by more than 80 million years,\u201d continued Marek. \u201cThey really set the stage for later life<\/a> on land, including humans and vertebrates<\/a>.\u201d <\/p>\n