The story behind the giant shipworm discovery that broke the internet
Eyes popped when news stories came out, complete with GIFs showing a slimy grayish-black worm-like creature falling down from what looked like a white tube as long as a baseball bat.
It’s a cringe-worthy, bizarre image, with various people and news organizations calling it an “alien,” the “stuff nightmares are made of.” Think of Alien (the movie), X-Files, or even the slugs of Stranger Things.
But there is so much more than what meets the eye in this giant shipworm discovery.
The giant shipworm, scientific name Kuphus polythalamia, is a member of wood-feeding and wood-boring bivalve mollusc family Teredinidae (shipworms), according to the study. Like its cousins clams, oysters, scallops, and mussels, it has an external shell that encapsulates a soft, backbone-less body. Another relative of this giant shipworm is the local delicacy in Palawan, a smaller, grayish shipworm commonly referred to as tamilok.
Like the Palawan tamilok, the giant shipworm found in Sultan Kudarat in Mindanao (exact location withheld due to security risks) is also considered as a local delicacy. Locals dive about 3 meters into the sea to fetch K. polythalamia and prepare it as kilawin (ceviche), or cook it as adobo. In fact, in the 2010 video that spurred the study, locals describe it as sweet, delicious and nutritious. They even attribute curative, aphrodisiac, and energizing powers to it.
While locals have known the giant tamilok for quite a while, the scientific world has yet to understand it.
Dr. Gisela Concepcion, head of the Concepcion Lab (Marine Natural Products Laboratory) of the University of the Philippines Marine Science Institute (UP MSI), told Rappler in an email that her team has been studying tamiloks since 2009, as part of the Philippine Mollusc Symbiont (PMS) research program. This program is funded by the United States National Institutes of Health, the Fogarty International, the US National Science Foundation, and the US Department of Energy.
After one of the Concepcion Lab researchers chanced upon the YouTube video of the giant shipworm, members of Concepcion’s team flew to Sultan Kudarat (about 1,300 km away from Manila) and got in touch with Sultan Kudarat State University researchers, headed by Prof. Julie Albano.
After some months, live specimens of the animal were brought to UP MSI to be studied. Together with collaborators from the University of Utah, they unravelled the secret behind the elusive marine creature.
“It's been a scientifically exhilarating and rewarding journey of discovery – unravelling one of the deep secrets of marine evolutionary biology,” said Concepcion.
K. polythalamia is the only living species in the group (genus) Kuphus, and is considered the longest bivalve mollusc in the world, growing to about two meters. Like other Kuphus species, the giant shipworm secrete a tube made up of calcium carbonate, which also serves as its shell.
But what separates K. polythalamia from other shipworm species is that it burrows on marine sediments rather than wood. It also harbors a type of bacteria that obtain energy using inorganic energy sources like hydrogen sulfide, iron, and ammonia. K. polythalamia thrives deep down the ocean mud, where decaying wood among other organic materials emit hydrogen sulfide, a colorless gas that smells like rotten egg.
According to the new research, the bacteria live in perfect harmony with the giant shipworm. It thrives in its gills and “make food” for it in a way that is similar to plants’ photosynthesis, only this time, the bacteria use hydrogen sulfide. This type of behavior, utilizing sulfide to produce energy is fairly common, especially for marine creatures living in extreme depths of the oceans where the sunlight cannot reach, and those that live near oceanic volcanoes and deep-sea vents.
Because of this symbiotic relationship, the digestive system of the giant shipworm has shrunk compared with its other family members that feed on wood.
“The lagoon where the giants were found had thick, muddy, anoxic water with lots of degrading wood, rich in hydrogen sulfide. We were told by the local folk that there used to be a lumber mill and a thick wooded area near the lagoon. Then sometime back, a lot of the trees/wood fell to the lagoon because of a typhoon and runoff,” said Concepcion.
The decomposing wood from a 1980s-era lumber mill in the area where it was discovered served as a stepping stone for the evolution of the K. polythalamia from wood-eating and wood-boring, to sulfide-feeding. The evolution is also reflected in the community of bacteria living in the gills of the giant shipworm.
The serendipitous discovery of the giant shipworm helps us understand better how some marine animals evolve overtime.
“I bow to this creature in awe and wonder, knowing we are far from fully understanding the mysteries it holds,” Concepcion said. – Rappler.com