Bone Eating Zombie Worms Use Acid to Drill Through Bones

Posted on July 2, 2012

Osedax

Scientists have discovered that tiny bone-devouring zombie worms (Osedax), known to both eat and inhabit dead whale skeletons and other bones on the sea floor, have the unique ability to release bone-melting acid. The worms are also known as zombie worms or boneworms. The findings pertain to the females only. The males never grow beyond their larval size (about 1 mm) and they live inside a gelatinous tube that surrounds each female. Each female has hundreds of males living in her tube.

The discovery was made by scientists at Scripps Institution of Oceanography, University of California, San Diego. The work is being presented at the Society for Experimental Biology's 2012 meeting in Salzburg, Austria.

Dr. Sigrid Katz, a postdoctoral researcher working with Greg Rouse and Martin Tresguerres, says, "These worms are unique in using bone as a habitat and nutrient source. We have learned a lot about these worms in the past 10 years, but one of the most intriguing questions has been how they penetrate bone and take up nutrients."

Osedax reach up to 3-4 centimeters in length. They have no mouth, anus or gut. Their digestion of the nutritious bone is made possible by their partnership with bacteria. Osedax were fist discovered on a whale carcass in 2002 by scientists from the Monterey Bay Aquarium Research Institute (MBARI).

It was clear the worms and their bacteria rely on nutrients such as collagen or fat from the bones they inhabit. However, until now it was a mystery how the worms penetrated the bones . Their bodies consist of a worm-like portion and 'roots' that house the bacteria and penetrate the bones, but they have no body parts mechanically able to drill through bone. Here is a MBARI video of the boneworms feasting on dead whales in Monterey Bay.

The researchers looked instead for signs of a chemical drilling strategy, testing for the presence of acid-secreting enzymes in different tissues of the worm. One of the enzymes, a proton pump, was abundant in the roots, the part of the worm that penetrates the bone. The results indicate that the worm secretes acid to demineralize the bones.

Photo: Greg Rouse


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