In case your nightmares are insufficiently full of terrifying real creatures, here is another one for you: there is a ferocious and venomous worm whose four fearsome fangs are built from copper. Bloodworms’ metallic teeth are used both for biting prey and fighting with rivals, but it has taken 20 years of research to reveal the biochemistry that makes this possible.

There is a lot to be said for metal teeth, at least if you’re the biter, not the bitee. Indeed the bloodworm’s (members of the genus Glycera) jaws, composed of 10 percent copper crystals, are so hardy a single set lasts their five-year average lifetime without needing to be constantly refreshed. They can bite through an exoskeleton and inject venom into their prey, paralyzing them. Their copper teeth may also act as a catalyst, enhancing the speed with which the bloodworm's venom acts.

Despite this, very few animals have harnessed the power of solid metal, both because of the difficulty of obtaining enough, and the challenges involved in integrating the metal into the jaw. Bloodworms have long been known to absorb sufficient copper from the intertidal sediments in which they live to address the first problem, and now a new paper in Matter has revealed how they manage the second.

The key, Professor Herbert Waite of the University of California, Santa Barbara and co-authors reveal, lies in what they call MTP (multi-tasking protein), which has six separate and essential roles in the making of those fearsome jaws.  “We never expected a protein with such a simple composition, that is, mostly glycine and histidine, to perform this many functions and unrelated activities,” Waite said in a statement.

The MTP helps the worm recruit Cu2+ ions, causes the mixture produced to separate like oil and water, catalyses the formation of the pigment melanin and assists in its polymerization, and integrates both the melanin and itself into films and fibers. Finally, it forms bridges between molecules using copper as a bridge

MTP provides the third known method for animals to form hydrogels alongside those used by vertebrates (humans included) to create cartilage and those squid and octopuses use as a step towards making their beaks. The previously unsuspected chemistry could prove pointers for industrial material synthesis.

Bloodworms get their name not from their aggressive biting, but from the fact their skin is so translucent their hemoglobin-rich body fluids can be seen beneath. They can grow to 35 centimeters (1.2 feet). Waite’s lab has been studying them for two decades, and clearly he admires their biological initiative. He appears less fond of their personalities, however, noting: “These are very disagreeable worms in that they are ill tempered and easily provoked. When they encounter another worm, they usually fight using their copper jaws as weapons.”