New genus of shipworm found in the Philippines feeds on stone

A new genus and species of shipworm, the first that burrows through stone rather than wood, has been discovered in the Philippines.

Shipworms are wood-feeding mollusks that are well known for destroying ships, wharfs and other wooden structures. But according to the paper written by researchers from the University of Utah, Drexel University, Northeastern University and the University of the Philippines Marine Science Institute, the new genus and species of worm-like clam which they called Lithoredo abatanica “lacks adaptations associated with wood boring and wood digestion” which are typical among previously described shipworms. Instead, this new kind of organism is “well adapted for rock boring,” burrowing through carbonate limestone in the bed and low banks of the Abatan River in Bohol. In fact, scientists found that a submerged wood near the bored limestone contained different wood-boring specimens but had no traces of the newly discovered organism.

While there are other animals that practice stone burrowing activities, what makes L. abatanica highly unusual is that it actually eats the stone as it burrows. A gut content analysis of L. abatanica shows that the ingested material has mineral content “closely matching the composition of the rock” in which the organism burrows. The digested material is expelled from the siphons as fine sand. Most shipworms depend on wood for food and so it is still unclear how the new genus and species obtains nutrition, considering that there are few nutrients in rocks.

Lithoredo abatanica. Photo courtesy of Dan Distel.

Lithoredo abatanica. Photo courtesy of Dan Distel.

L. abatanica‘s burrowing activity has a huge impact on its environment so much so that the researchers have dubbed the organism an “important ecosystem engineer.” Its burrowing leads to the massive erosion of stony riverbanks and creates new habitat for aquatic animals such as fish and crabs that use the abandoned burrows. This new discovery also has important implications in the field of paleontology. Fossil borings in rock are thought to mark ancient marine habitats. But the presence of L. abatanica opens up possibilities that such fossils could have originated from fresh water. 

The breakthrough research is part of the larger project of the Philippine Mollusk Symbiont International Collaborative Biodiversity Group of which Dr. Gisela P. Concepcion, professor at the Marine Science Institute and former vice president for academic affairs, is one of the principal investigators.

Burrows made by L. abatanica on a carbonate limestone. Source: Proceedings of Royal Society B/

This new discovery follows an earlier paper where the researchers reported a new genus of wood-boring shipworm, the first to be discovered after almost a century. The new genus and species was found in Balayan Bay in Batangas.