A tusk-like, 3- to 5-foot-long mollusk is the theme of a research paper published earlier this year in the Proceedings of the National Academy of Sciences journal, authored among others, by former Scripps Institution of Oceanography scientist Margo Haygood, now research professor in medicinal chemistry at the University of Utah (and the daughter of La Jollans Ken and Noreen Haygood).
The animal belongs to the shipworm family and has been known to exist for centuries, but only recently have scientists had the opportunity to study it — and its surprising bacteria ecosystem. “We were able to examine the animal other than just looking at its shell, which comes to the shell collectors’ market pretty often,” Haygood said.
Shipworms are a group of saltwater clams who’ve adapted to living in rotting wood, thanks to the bacteria within them that transforms that wood into food. The giant shipworm, named “Kuphus,” went one step further and lived in a muddy, high-sulfur environment, which would be toxic for many other lifeforms, 80- to 100-million years ago. “We’ve been able to study the evolution of the family, and this animal falls in the middle of that family, so its ancestor was a wood-eating shipworm, and it switched its bacteria and its metabolism. It’s really absolutely wild,” Haygood said.
Kuphus also uses bacteria to obtain nourishment, but unlike its shipworm cousins, Kuphus relies on beneficial bacteria living in its gills that use hydrogen sulfide as energy to produce organic carbon to feed the shipworm. As a consequence, its digestive system has been reduced in size and importance.
The long, black, slimy body of the giant shipworm reminds Haygood of an alien. She marveled at the fact that “here we are in the 21st century and we can have a first encounter with a strange organism from our own world.”
The encounter was serendipitous, Haygood said. “One is one of the younger scientists in our group saw a documentary telling about these animals (in the Philippines). We were able to make contact with the local authorities to get to these animals, and the thrill was being able to bring one of them to the university in Manila.”
The animal’s shell, produced by secretions like any other mollusks, has a tube form. It’s capped on one side and on the other side are two openings that Haygood explained are used to pump water in and out. “Like you would see in a clam; one pumps water in and the other one shuts water out,” she said. The water is filtered through gills, and the bacteria come into action to transform sulfur into food inside the Kuphus.
Haygood said she studies shipworms for their potential for discovering new antibiotics. “We don’t think this animal is going to be useful in that, because it doesn’t eat wood. Its importance is more that it sets all the other shipworms in context and provides a contrast, supporting ideas about the importance of antimicrobial compounds. It’s also a very surprising evolutionary discovery,” she added.
The research “Discovery of chemoautotrophic symbiosis in the giant shipworm Kuphus polythalamia (Bivalvia: Teredinidae) extends wooden-steps theory” published in Proceedings of the National Academy of Sciences was authored by Daniel L. Distel Marvin A. Altamia, Zhenjian Lin, J. Reuben Shipway, Andrew Han, Imelda Forteza, Rowena Antemano, Ma. Gwen J. Peñaflor Limbaco, Alison G. Tebo, Rande Dechavez, Julie Albano, Gary Rosenberg, Gisela P. Concepcion, Eric W. Schmidt and Margo G. Haygood.