http://www.digitaljournal.com/tech-and-science/science/scientists-find-extremely-rare-live-giant-shipworm-in-philippines/article/490609

Scientists find extremely rare live giant shipworm in Philippines

Posted Apr 18, 2017 by Karen Graham
We have known about giant shipworms for a long time but no one has ever seen a real live specimen until now. Scientists got their first look at some of the strange creatures after spotting their shells on a YouTube video.
Opening the cap on a giant shipworm shell.
Opening the cap on a giant shipworm shell.
University of Utah
The giant shipworm, (Kuphus polythalamia), is actually not a worm at all, but a member of the mollusk family. We have known they existed because when they die, they leave their huge, tusk-like shells behind. The shells were first described in the 1700s and are still eagerly sought by collectors. Giant shipworms can reach up to 1.55 meters (5feet) in length and 6.o centimeters (2.3inches) in diameter.
A YouTube video of a cluster of giant shipworm shells poking out of the muddy seafloor of a shallow bay in the Philippines that had once been used to store logs caught the attention of scientists.
After obtaining five specimens of the live worms, an international team of researchers, led by the University of Utah, Northeastern University, University of the Philippines, Sultan Kudarat State University and Drexel University, studied and dissected one of the creatures. Their findings were published in the April 17 issue of the Proceedings of the National Academy of Sciences (PNAS).
The giant shipworm feeds from a valve (marked V) and has two siphons at its tail (marked S) to take ...
The giant shipworm feeds from a valve (marked V) and has two siphons at its tail (marked S) to take in and expel water
PNAS
Lead investigator Daniel Distel, Ph.D., a research professor and director of the Ocean Genome Legacy Center at Northeastern University, says that scientists didn't really know for sure what the animal's preferred habitat was. That is until they viewed the video. An expedition was set up and the team was rewarded with live specimens.
A video shows Distel carefully washing the mud-caked shell of one of the specimens and then very carefully tapping off the outer cap, revealing the living worm, reports the BBC. "It's sort of the unicorn of mollusks," University of Utah marine biologist Margo Haygood says in describing the long, slimy black creature.
Researchers discovered the cap covering the creature's shell seals over its mouth, and it's presumed this keeps the worm from feeding directly on the sediment. Dissection showed there was very little fecal matter in the digestive system, leading everyone to wonder just what did the worms eat?
Diagram showing the digestive process in the giant shipworm.
Courtesy of the University of Utah.
Diagram showing the digestive process in the giant shipworm. Courtesy of the University of Utah.
PNAS
The shipworm's relatives are adept at boring into soft, soggy submerged wood. By using their symbiotic relationship with bacteria living in their gills, they are able to digest the wood particles they churn up. The giant shipworm is a less discriminating diner, though.
Giant shipworms can set up housekeeping in muddy seafloors or rotting wood, so scientists suspected wood wasn't its main source of food. The team suspected the worms were digesting hydrogen sulfide, released by rotting vegetation and dead animal carcasses.
However, hydrogen sulfide isn't that nutritious, so that fact raised another question. Did the worms have symbiotic bacteria? The bacteria would be needed to break down the inorganic compound, hydrogen sulfide, into a more nutritious carbon for them to eat. And luckily, electron microscopes showed the presence of the bacteria in their gills.
Haygood sums it up pretty well, saying, “We think of this planet as being well explored, but I think there’s plenty of room left for exploration. We should not believe that we know all there is to know about the biology of our planet.”