How bloodworms make their unique copper teeth

Like something out of a horror movie, bloodworms (Glycera dibranchiata) have pale skin that allows their red body fluids to show through and are known for their strange fang-like jaws. These are made of protein, melanin, and concentrations of copper – a characteristic found nowhere else in the animal kingdom.

For the first time scientists have discovered how these worms use copper harvested from marine sediments to form their jaws, identifying a new multi-tasking protein described in a study published in Matter.

Bloodworms can burrow through intertidal mud (where the ocean meets the land between high and low tides) to a depth of several metres, kind of like the sand worms in Dune – except there’s more water and they only grow up to 35 centimetres in length.

They feed through everting their proboscis – an extensible tubular sucking organ (gross) – equipped with four black, hollow jaws that latch onto and inject paralysing venom into other unfortunate creatures during hunting and combat.

“These are very disagreeable worms in that they are ill tempered and easily provoked,” says co-author Professor Herbert Waite, a biochemist at University of California, Santa Barbara, in the US. “When they encounter another worm, they usually fight using their copper jaws as weapons.”

These spikey murder tubes are also capable of puncturing straight through an exoskeleton, so the jaws need to be strong and tough enough to last through the bloodworms’ entire five-year lifespan, since they only form once.

The bloodworm’s jaw making process

Waite’s lab has been studying bloodworms for 20 years, but only recently were they able to observe the entire chemical process that forms the jaws, from start to finish.

It relies on a protein they’ve identified for the first time – a histidine and glycine amino-acid-rich compound called multi-tasking protein (MTP) – that performs six distinct functions critical for jaw formation and performance and acts as the primary structural protein in bloodworm jaws.

MTP recruits copper ions (Cu²⁺) to form a complex and then concentrates itself into a viscous, protein-rich liquid that is high in copper and phase-separates from water (think: how oil and water don’t mix).

The protein then uses the copper to catalyse the conversion of the amino acid derivative DOPA (dihydroxyphenylalanine – say that five times fast) into melanin polymers; it then integrates melanin and itself into thin films and fibres.

This all gives the jaw mechanical properties that resemble those of manufactured metals.

Like an evil genius, the worm is able to use this process to easily synthesise a material that, if created in a lab, would require a complicated process involving many different apparatuses, solvents, and temperatures.

“We never expected protein with such a simple composition, that is, mostly glycine and histidine, to perform this many functions and unrelated activities,” says Waite.

The interdisciplinary team hopes that by gaining a better understanding of how the bloodworm conducts its self-contained processing laboratory, this could help to streamline aspects of production that would benefit industry.

“These materials could be road signs for how to make and engineer better consumer materials,” says Waite.

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