Lithoredo abatanica is an organism with an unusual appetite: this creature eats stone. And when it leaves, sand comes out, the remnants of a still-mysterious digestive process.
The mollusk, which was dug up in the Philippines from the bottom of a river, was presented this week by an international group of scientists in Proceedings of the Royal Society B. It is a shipworm, a group of burrowing animals, with shells but are so different from known examples that it is both a new species and a new genus.
Ship worms are usually known to eat wood. Just the thing in the name: they use their shells attached to one end of their bodies as chewing devices to dig and consume in ship floors, docks and other dipped wood . Behavior has made them a sailor's plague past and present, and more recently they even have the joys of at least one pier in New York [1
Wood-eating ship worms fascinate scientists because they digest pulverized wood with the help of symbiotic bacteria that live in their gills. The bacteria produce a range of enzymes and other substances, and their investigation and finding new shipworms could prove helpful in finding new antibiotics, a topic that interests scientists behind the new release.
They first heard reports of a mysterious shipworm phenomenon in the Abatan River on Bohol Island a few years ago, organized by an expedition of the French National Museum of Natural History. Reuben Shipway and Daniel Distel of Northeastern University, members of the Philippine Mollusk Symbiont International Collaborative Biodiversity Group, set out in search of creatures with snorkel masks and chisels in tow.
A local resident proposed to investigate the bottom of the river. Underwater, they discovered huge sandstone boulders with holes. Out of some of the rocks protruded the twin flags of the shipworm siphons, organs that exude the creatures.
"At that time we knew that we had met shipworm gold," Dr. Shipway.
The researchers took the translucent white creatures out of their caves and performed various tests and preparations. At this time they learned more about the fascinating lifestyle of L. abatanica.
The appendix, a large organ for the digestion of wood, which is common in shipworms, was missing in the new species. However, the entrails of the ship worms were full of fragments of stone. The chemical analysis showed that it was the same stone in which the animals lived. What came out was stone too.
"We had a few animals in a makeshift aquarium," Dr. Shipway, "and you could put the animals in the aquarium and basically watch them drop fine particles of sand out of their siphons. "
What exactly the ship worms get from the stone is not yet clear. One possibility, the researchers speculate, is that the granules could help them grind up plankton and other living creatures floating in the water, much like gizzard stones help birds break up the food they swallowed.
But it may be that the worms are able to extract nutrients from the stone in an unprecedented way. The gills of the stone-eating ship worms are much larger than those of other ship worms, suggesting that the tiny inhabitants of the organ may be particularly important to the creature's survival. The team is now working to sequence the genomes of L. abatanica symbionts to identify them and gain insight into how their metabolism works.
"It already looks very, very interesting," Dr. Thistle. "What we can say is that the bacteria we find in the gills are not related to the bacteria we've found in any other shipworm so far."