Zombie worms with bone-melting acid

Deep-sea worms that live inside dead whale skeletons have a unique ability to release bone-melting acid, biologists from California have discovered.

Osedax worms are just four centimetres long at most, have no mouth, anus, or gut, and have no body parts that could drill through bone. Researchers at Scripps Institution of Oceanography, University of California, San Diego wanted to know how these miniscule worms bore through bone.

They investigated the worm to see if its drilling strategy was chemical in nature. The team looked for acid-secreting enzymes in different tissues of the worm. They found one of the enzymes, a proton pump, that was abundant in the part of the worm that penetrates the bone.

The potent poison released demineralises the bone, creating a hole in the skeleton that reveals enclosed fat and oil. A symbiotic bacterial partner digests the fat and releases nutrients that the so-called zombie worm can absorb.

Only female worms are equipped with these acidic enzymes. Males never grown beyond millimetre-long larvae, and live inside a gelatinous tube that surrounds each female. A single female will have hundreds of males living in her tube.

The Osedax genus was first discovered in California's Monterey Bay in 2002. It was described in the journal Science in 2004.