New shipworm may hold a key to future discoveries

Consider the clam. Imagine that its two shells have shrunk into a collar, fringed with jagged teeth used to gnaw through wood. Imagine that its digestive tract and most of the rest of its organs have gotten pushed out the back door of the shell, forming a long streamer of flesh that it keeps safe by burrowing into the wood it eats. And imagine that it is larded with symbiotic bacteria that aid the creature in the digestion of all that wood.

Congratulations: You have arrived at the shipworm.

Shipworms and their wood-eating loomed large in the fears of sailors for centuries, as they can send a vessel to the bottom with little more than concerted munching. But they are also intriguing as potential sources for new antibiotics, which led a team of researchers to the Philippines last year where they found a new species of shipworm, which they named Tamilokus mabini.

The discovery, reported in the journal PeerJ earlier this month, occurred during a feverish episode of wading in mangroves and scuba diving in search of wood that had shipworm burrows. The team extracted the worms and brought them to their hotel-rooms-cum-biology labs.

Working quickly allowed the team to identify and begin the process of sequencing the DNA of the animals and their bacterial symbionts right away. When Reuben Shipway of Northeastern University, one of the study’s co-authors, extracted one of the shipworms, he knew he was looking at something new. “This is probably a new species, immediately just from looking at the siphons,” he said he recalled thinking, as he examined the tubular structures that allow the worms to expel waste. “They were pink and pinstriped.”

Back in a lab in Boston, the researchers confirmed that the pink-striped shipworm, which can range in size from about 2.5 to 6 inches long, was not only a new species but also a representative of a new genus. They explored its insides using a type of CT scanning and learned that its organs are arranged in a pattern unusual even for a shipworm. Not only have its heart and kidneys swapped places, but one portion of the digestive system is extremely long. “It’s about six times as long” as that of most other shipworms, perhaps to help in the processing of its food, said Dan Distel, also of Northeastern.

The researchers now plan to sequence the genomes of the bacteria that live within the new shipworm to learn what they are and what kinds of substances they make. Studying those bacteria could provide new leads for substances that are useful to people, like digestive enzymes that could help make biofuels.

“This is probably a new species, immediately just from looking at the siphons. They were pink and pinstriped.”

– REUBEN SHIPWAY, RESEARCHER