Thousands of poisonous centipedes have been swarming train tracks in the dense, forested mountains of Japan for more than a century, forcing trains to stop. These ‘train centipedes’, so-called for their famous obstructions, would appear every time – and then disappear again for years at a time. Now scientists have figured out why.
It turns out that this millipedes (Parafontaria laminata armigera), endemic to Japan, has an exceptionally long and synchronous eight-year life cycle. Such long “periodic” life cycles – in which a population of animals simultaneously moves through the life stages – have only been previously confirmed in some species sikkades with 13- and 17-year life cycles, as well as in bamboo and other plants.
“This millipede is the first arthropod non-insect among all periodic organisms,” said senior author Jin Yoshimura, an emeritus professor in the Department of Mathematics and Systems Engineering at Shizuoka University in Japan. did. decades.
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Train operators in Japan first saw an outbreak of centipedes in 1920; they had to stop their train briefly while waiting for the creepy crawlers to cross the tracks. According to various reports, the millipedes returned every eight years thereafter, each time forming a dense blanket that was impossible to pass through. In 1977, first author Keiko Niijima, a researcher at the Forestry and Forest Products Research Institute, first suggested that they could have periods of eight years.
Now Niijima, Momoka Nii, also a professor in the Department of Mathematics and Systems Engineering at Shizuoka University, and Yoshimura confirmed the life cycle through reports of historical outbreaks and detailed surveys. Over many years, the authors have collected millipedes from the mountains in Honshu, Japan, and conducted research on the insects; they determined their life stages by counting the number of bones and body segments, as this is especially true for the age of a millipede.
The researchers found that several broods of this population each have their own synchronization; in other words, one brood may be in the egg phase, while another may be mature adults. Each population rides through its entire life cycle in eight years.
The brood of millipedes that appears on the train track from time to time has no affinity with train tracks or is disruptive; rather, the insects only try to reach nutrient soils that are sometimes on the other side of the tracks. It just so happens that the railroad is an “obstacle” in their journey to new feeding areas, Yoshimura told WordsSideKick. To survive, this train munches millipedes on dead or decayed leaves pressed between the ground and the fresh leaves on the surface, Yoshimura said.
Because they live in such large numbers, the adults and the seventh nymphs – the stage before they become adults – quickly feast on all available food where they are born; and so they begin a trek to move to a new feeding area, he said. In that second place they eat the rotting leaves, mate, lay a bundle of new eggs and die later.
The researchers suspect that their prolonged life cycles may be synchronized with hibernation. Unlike periodic cicadas that occur in mass numbers and which therefore make each individual less likely to succumb to predators, this millipede train does not need any extra protection against predators. They already have a pretty good defense mechanism: if attacked, they release the poison cyanide, the researchers said.
The findings were published in the journal on January 13. Royal Society Open Science.
Originally published on Live Science.