Meet the chalk-chomping clam

There is a strange shipworm that is actually a clam. Stranger still is that it “eats” limestone by burrowing through the rock (instead of wood) and ingesting it. The ingested rock is then grinded inside its body before the antingaw, as locals in Bohol call the mollusk, expels the fine sandlike particles through its siphon, according to Sci.

A 2019 paper that detailed the antingaw’s discovery in the Abatan River of Bohol found limestone in its stomach. Two jagged shells on its head enable the antingaw or Lithoredo abatanica to bore holes on a rock where it also lives.

While it is a clam, the antingaw has no shell and looks like a worm with a soft body. It is eaten as a delicacy long before its discovery.

The University of the Philippines’ Marine Science Institute (UP-MSI), which is studying the rare species, has nominated the antingaw for International Mollusc of the Year (IMY).

IMY is an annual competition hosted by the German research institute Senckenberg Society for Nature Research, its marine conservation arm Senckenberg Ocean Species Alliance, and the international research society Unitas Malacologica.

The antingaw is a finalist in the contest and is vying for the prize against candidate mollusk species nominated by researchers from Italy, Australia, Seychelles and the United States. The results will be decided by public vote. The voting, done through the official voting form https://universityofalabama.az1.qualtrics.com/jfe/form/SV_bPWhKQXZjWJmwgm, ends on 26 April.

The grand prize is a complete sequencing of the winner’s genome. Having detailed genetic information will be a major step in using the antingaw to develop biotechnology products.

UP-MSI is already looking into creating biotechnology products with the antingaw and other shipworms with the support of the Department of Science and Technology-National Research Council of the Philippines. Through the “Teredinids and Associated Microbes: A Multi-level Investigation of Lifestyles and Outstanding Compounds as Sources of Novel Therapeutics” or TAMMILOC Project, UP-MSI is investigating shipworms and the microbial symbionts that aid in wood digestion.

The mechanism of how this odd animal gets nutrients from rock remains a mystery. Scientists think that the antingaw may harbor symbiotic microorganisms in its gills that help break down its inorganic diet, similar to how the tamilok hosts bacteria that helps break down mangrove wood.