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Worm architects build seaworthy sandcastles with own ‘glue’

There’s more than a grain of truth to the story of the sandcastle worm. Phragmatopoma californica, a bristle worm and resident of the intertidal zone, is a one-stop architectural firm, home-improvement supplier and construction company. Using sand grains and shell bits for masonry and its own glue for binding, the worm builds and maintains its own tubular living space. Though surprisingly sturdy, sand tube concretions aren’t as durable as concrete so, for extra support, the worms build their abodes in tight-knit colonies, some many feet across. En masse, when collectively viewed from the open ends, I think the tubes resemble roofing made from laterally stacked pipes.

Though an adult worm measures about 1 inch long and one-eighth-inch in diameter, it builds the tube several inches long. There it stays, with only a crown of lavender tentacles projecting from the opening, and these only exposed when the tube is submerged. The tentacles gather food and snag sand grains and shell pieces for building, then tiny, hair-like cilia move the material down the tentacles. Food is sent to the appropriate place for digestion while the building bits are sent to the worm’s fleshy, pincerlike “building organ,” which grasps and glues the material on to the part of the tube under construction. After secreting two little dabs of glue onto the particle, the building organ deposits it on to the end of the tube, holding it there for about half a minute, even wiggling it, to assure the glue has set. If everything feels right, the pincer releases.

What is this mysterious excretion that is secreted in liquid form and quickly hardens to a solid, processes that occur without the glue dissolving into surrounding ocean? Some biomedical engineers have not only figured out the worm’s secrets but have been inspired to duplicate the sticky stuff, hopefully for future clinical use. Developing a safe, effective, injectable medical adhesive would be a boon to orthopedic surgeons when they need to reconstruct shattered bones.

Researchers have discovered that the sandcastle worm uses shifts in pH to trigger the glue to harden. The acidic environment inside the worm maintains the glue as a fluid. Once exposed to seawater, which is slightly alkaline, the glue solidifies. (As an aside, if you’ve heard about climate change and ensuing ocean acidification, here is an example of a marine life species whose very existence demands the ocean maintain an alkaline environment.) Anyway, the researchers re-created a synthetic version of the worm’s actual concoction, which also boasts properties of water-solubility without dissolving in liquid. However, the lab version is at least as strong as Super Glue and twice as strong as the worm’s original recipe. Preliminary cell-culture experiments show no toxic effects and no unusual immune reactions, furthering cautious optimism because some medical-grade glues are highly inflammatory.

If the glue turns out to be all it seems, small bone fragments will be able to be precisely reconstructed, reducing the need for metal hardware. Typically, surgeons use metal pins and screws to repair shattered bones but bone shards are tricky to set, not only because fragments are difficult to align but because it’s not a sure thing the alignment will hold throughout the healing process. Having a liquid adhesive may solve these challenges and render superior healing. Looking ahead, the synthetic glue could also multitask by piggybacking drugs like painkillers, growth factors, antibiotics, anti-inflammatory medicines or even stem cells to sites where bone fragments are glued. Continuing research will reveal whether this is really the magic glue clinicians having been awaiting.

There are infinite reasons to safeguard our ocean and treat it as a long-term investment. Financial input to understanding the biology and ecology of the ocean is part of that investment, and the sandcastle worm is a reminder of this. If no one pursued basic studies of the worm, we wouldn’t be tipped off to copying its chemistry to create novel adhesives for use in resolving our singular problems. At this point, we don’t a have a minute to waste in quest of unraveling the subtle, complex underpinnings that weave together the web of life. The ocean leads, and the rest of the planet follows.


— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Send comments to