Glycera dibranchiata is exactly the kind of creature you don’t want to find at the bottom of your beach bucket. They are called bloodworms for their translucent skin. Long and poisonous, the worms are native to both coasts of North America and have four sharp fangs and a somewhat grumpy temperament: when they dig in the sand, they attack anything they detect nearby.
“They become very protective of their territory,” said Herbert Waite, a professor at the University of California, Santa Barbara, who studies the creatures. “I think they’re fundamentally introverted.”
When displeased, the worms fire a specially constructed proboscis to seize their prey.
“You can imagine that if your head was a balloon, normally it gets sucked into your body. Then when you want to eat, you puff it up and bite it, then suck it back in,” said William Wonderly, a chemist also in Santa Barbara who collaborated with Dr. Waite to study the creatures. “It reminds me a lot of the aliens in ‘Alien’, where they have little mouths that they pull out and retract.”
Worms have another less obvious but equally strange feature. Their fangs, which grow from specialized cells on their skin, are devilishly tough and made of only three ingredients, including melanin. While melanin is one of the pigments responsible for the color of human skin and hair, bloodworms make it into a tough, copper-infused material, which makes up about 10% of fangs by weight. . But how the worms achieve the chemical transformation was a mystery.
In a paper published Monday in the journal Matter, Dr. Wonderly, Dr. Waite and their colleagues revealed that the creatures do this by relying on the third ingredient in fangs, a deceptively simple protein with many talents. The discovery reveals a biochemical secret of this unusual creature and highlights how nature finds surprisingly simple ways to create complex anatomical features.
A bloodworm’s fangs grow from a collection of cells that function as hoppers, storing materials for their assembly, Dr. Wonderly said. The team examined the proteins used in these cells and identified one, called the multitasking protein, as a major component of the final product. This protein, they report in the new paper, is composed mostly of just two amino acids, a small number, but it plays a crucial role in the assembly of the croc.
The scientists found that the protein catalyzes a reaction to create melanin and recruits copper ions. Then it bonds the melanin into polymers, assembles with the melanin into a structure, and uses the copper to seal it all together. Essentially, the multitasking protein appears to steer melanin away from its tendency to form in the drops you’d see under a microscope in human hair and skin, Dr. Wonderly said. This allows him to become something entirely different: part of a deadly killing machine lurking in the sand.
Not all the mysteries of the bloodworm are solved: little is understood about how the organism first developed this system and how copper is handled in the body of the worm.
“A huge question is how copper gets concentrated in the jawbones,” Dr. Wonderly said. “To really understand, you would need the baby worms. But because they have a complicated spawning cycle, they are difficult to grow in the lab.
The team hopes to learn more about how the worms assemble this unusual polymer by tracing how melanin is produced and how the worm constructs it from precursors in its body.
“There are so many things that nature has figured out how to do very efficiently and cleverly,” Dr Waite said. “It requires basic science and childlike curiosity to discover.”