This species of shipworm sources energy from hydrogen sulfide, commonly found in rotten eggs and human flatulence, which can be highly poisonous and corrosive in high amounts.
Image credit: Jen Viegas
A rare species of giant shipworm has mostly lived in myth since its 3 to 5 foot-long tusk-resembling shells were first documented in the 18th century. Shipworms — which are actually a type of saltwater clam — once conquered the seas by feasting on wood, sinking ships in the process, but this particular species, Kuphus polythalamia, was recently found planted like carrots in mud at the bottom of a lagoon in Mindanao, Philippines.
The stench of the site, which was previously used as a log storage area, was overwhelming, yet researchers from Sultan Kudarat State University managed to collect five live Kuphus individuals, allowing them to study the live specimen inside the shell for the first time.
The scientists packed their precocious cargo into PVC pipes and escorted the shipworms to the University of the Philippines, where Daniel Distel and his team eagerly awaited their arrival.
“We really did not know what to expect,” Distel, a research professor and director of the Ocean Genome Legacy Center at Northeastern University, told Seeker. “Most clams are white or beige or pinkish inside.”
His colleague Margo Haygood described the moment when they first set eyes on the live giant shipworms.
“We turned the pipes upright and filled them with seawater and airstones and put the animals in to acclimate," she recalled. "Before long, I looked into the pipe and could see a strong jet of water coming out of the animal’s siphon. It was alive!”
“The animal inside is dark gray, shiny and floppy,” added Haygood, who is a research professor in medicinal chemistry at the University of Utah College of Pharmacy. “It looks like an alien creature.”
The scientists determined that, unlike other shipworms, which munch on wood in the ocean, Kuphus depends on two primary things for its survival: hydrogen sulfide and beneficial bacteria that live in its gills. Hydrogen sulfide, commonly found in rotten eggs and human flatulence, is very poisonous, corrosive, and flammable in large amounts.
Kuphus loves it, though. Distel explained that the bacteria burn it “the same way we burn carbohydrate or sugar to make energy.” The bacteria-made sugars are ultimately what the shipworm lives on. It would seem to have an endless supply of hydrogen sulfide, since its organic-rich mud habitat emits the smelly gas in large quantities.
It is a mystery as to how Kuphus evolved this unusual mode of survival. What is known is that its wood-eating relatives have had a tougher time finding food since human activity has actually reduced the overall amount of wood in the oceans.
Distel explained, “Most wood gets in the oceans via erosion of coastal forests and riverbanks. People like to clear forests away from coasts and riverbanks so they can build homes, businesses and resorts. We also like to build dams and have dammed most of the great rivers of the world. As a result, a lot less wood makes it to the sea.”
Wooden ships have helped to spread shipworms around the world, so somehow Kuphus wound up in the shallow Philippine lagoon, and gradually evolved its unique way of life.
In some locations, people even eat shipworms, which have been described as being “a little more earthy tasting” than typical clams.
Haygood has more in mind than just a giant clam feast. She told Seeker that bacteria harbored by wood-eating shipworms have “potential as sources of industrial enzymes for converting cellulose to sugar and for new antimicrobial drugs.”
On the other hand, she said, Kuphus “is valuable just because it's so strange and marvelous.”