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Decapitated worms regrow their brain

Ribbonworm (Tubulanus sexlineatus) to re-grow a head, which is seen as the lighter-pigmented part on the left side. (Credit: Terra C. Hiebert)

For some worm species, decapitation is not a big deal, but they grow a new head.

But many of these superpower is an ancient skill, a recent study suggests that this ability is a relatively recent adaptation, at least evolutionarily speaking.

Regeneration is unusual in animals, but the species that can be sprinkled in the animal kingdom, and include sea stars, hydras, fish, frogs, salamanders, spiders, worms. Regrowing parts of the body for a long time was thought to be a old property, with a variety of animals to detect the possibility of a distant common ancestor that probably originated hundreds of millions of years ago.

But for some species of marine ribbon worms, have the capacity to grow severed heads, and the brain traces back to only 10 million to 15 million years ago, making it a much more recent adaptation than previously thought, scientists found. [Photos: Worm Grows Head and the Brain of Other Species]

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In the study, researchers collected data on 35 species of ribbon worms in the phylum Nemertea, snipping the heads and tails of individuals in 22 species. They discovered that all of the species can regrow an amputated tail, “but surprisingly little was able to generate a full head,” the scientists wrote in the research. (The headless worms have survived for weeks or months after their decapitation, however.)

Five species of worms were documented regrowing the head and the brain: the four of them seen for the first time, and that was formerly known for head regeneration. In addition, the researchers found evidence in previous studies of the head-grows in three ribbon worm species.

Their results show that the ancestor of all ribbon worms probably could not regrow a severed head, and that head growing arose independently in only a handful of the worm species. This also raises important questions about all the animals that can regenerate parts of the body, the researchers wrote.

“We compare the groups of animals we cannot assume that the similarities in their ability to regenerate and to reflect a shared origin,” study co-author Alexandra Bely, a professor of biology at the University of Maryland, said in a statement.

The findings are published online March 6 in the journal Proceedings of the Royal Society B.

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Originally published on Live Science.

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