Parchment worms are best pinched in the dark

Tube-dwellers make a mysterious glowing mucus

GLOW WORM  Parchment worms use their filmy flaps to pump water through the tubes they build around themselves. This one has been removed from its U-shaped home.

D. Deheyn/Scripps Inst. of Oceanography, UCSD

Oh go ahead. Squeeze the soft tube of a parchment worm. But gently.

If it’s dark, “you will see puffs of blue mucus come out,” says Dimitri Deheyn. And the blue is glowing.

How the ocean-dwelling Chaetopterus parchment worms create the long-lasting glow — and the soft-but-tough tubes themselves — are still substantial mysteries, Deheyn says. 

Parchment worms spend their adult lives inside the U-shaped tubes they create, with just the rounded base buried. They live in sea bottoms around the world, from deep ocean canyons to marine shallows. When Deheyn first shows worms to visitors at his laboratory at Scripps Institution of Oceanography in La Jolla, Calif., sometimes “they are ready to faint because they are not expecting such a weird-looking creature,” he says. (Watch Nature’s Glowing Slime to see worms in Deheyn’s lab.)

Parchment worms spend their entire lives in their tubes and can’t live long outside them. D. Deheyn/Scripps Inst. of Oceanography, UCSD

Fleshy prongs fan out of the worm’s flattened head, and a few pairs of gossamer paddles flap like wings near its middle, a motion that pumps seawater through its tube. “They don’t bite, they don’t sting,” Deheyn says. At most, troubled worms secrete a gust of mucus. The puff floats away from the body and “glows for minutes and minutes and minutes.” This persistent luminescence wouldn’t be surprising in bacteria or fungi, but it is very strange for a worm. Explaining worm-shine’s chemistry and function remains a challenge. Depriving the mucus of oxygen — which normally turns off luminescence — has no effect, Deheyn and his colleagues reported last year.

Some biologists have suggested that the worms also use the mucus to construct their tubes, which feel like rolled-up paper. Deheyn has stored some in water for almost 10 years, and they haven’t fallen apart yet. In air, they maintain the same responses to various tugging and pressing stresses whether the temperature is –75º Celsius or 250º C, he and his colleagues report July 9 in the Journal of the Royal Society Interface. Such stable parchment could come in handy as an alternative to metals and polymers, or maybe even form the basis of a 3-D printable material, he says. If he can figure out how to make it. 

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