Image of the Day: Regenerating Worms
Image of the Day: Regenerating Worms

Image of the Day: Regenerating Worms

Planarian flatworms grow to double their normal size when scientists inhibit a gene that suppresses growth.

Amy Schleunes
Amy Schleunes

A former intern at The Scientist, Amy studied neurobiology at Cornell University and later earned her MFA in creative writing from the University of Iowa. She is a Los...

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Feb 3, 2020

ABOVE: A flatworm whose “degrowing” phase was suppressed towers over a control worm

Repressing a gene in planarian flatworms (Schmidtea mediterranea) that prevents stem cells from producing a key growth factor results in the animals doubling in size, report the authors of a study published on January 20 in Current Biology.

The flatworms are known for their extraordinary ability to regenerate themselves after almost every kind of injury, a process that involves a growing phase followed by a “degrowing” phase during which the worm is scaled back to restore its proportionality. It was the rescaling phase that the researchers blocked in the study.

“These worms have essentially discovered a natural form of regenerative medicine through their evolution,” says Christian Petersen, who studies regeneration at Northwestern University and is coauthor of the paper, in a university press release. “Planarians can regenerate their whole lives, but how do they limit their growth? Our discovery will improve understanding of the molecular components and organizing principles that govern perfect tissue restoration.”

E.G. Schad, C.P. Petersen, “STRIPAK limits stem cell differentiation of a WNT signaling center to control planarian axis scaling,” Current Biology, doi:10.1016/j.cub.2019.11.068, 2020.

Amy Schleunes is an intern at The Scientist. Email her at