Cultivating shipworms requires just wood and water and yields tasty clam-like meat
by Science Writer Kim Woolcock
Finding foods with a lower carbon footprint is essential to curbing our greenhouse gas emissions, and “blue foods,” sourced from aquatic environments, may offer one solution. Researchers in the UK are investigating an innovative possibility: shipworms. These historically hated organisms are not worms at all, but relatives of clams and mussels. They are fast-growing, high in vitamin B12, and can convert waste wood into a healthy source of protein. The researchers have dubbed them “naked clams” and reported their results in Sustainable Agriculture on November 20, 2023. The open-access article is titled “Naked Clams to Open a New Sector in Sustainable Nutritious Food Production.”
Shipworms—also called teredinid worms—tunnel through sea-soaked wood, making it their home and their food. They historically destroyed innumerable wooden ships and continue to eat their way through billions of dollars of coastal infrastructure, such as piers and jetties, each year. Despite their name, they are not worms; they are bivalves, relatives of filter-feeding clams and mussels, but with their shell reduced to a tiny thing that they use as a drill bit to bore into wood, scraping away shavings that they digest with the help of bacterial microsymbionts in their gills.
Teredinid worms were farmed by Aborigines in Australia, and they are eaten raw or in curries in southeast Asia. They are reported to taste like clams, and they are rich in nutrients, fast-growing, and easy to culture. Recognizing their potential value as a low-input, protein-rich food source, David Willer at University of Cambridge and J. Reuben Shipway at University of Plymouth and co-workers developed a simple indoor method to culture naked clams and compared their nutritional value to that of the commonly cultivated blue mussel (Mytilus edulis). They also tested out the effects of feeding the naked clams algal supplements, to boost their nutritional value.
Shipworms find and settle on their wooden homes/buffets when they are still larvae, so the researchers collected the larvae for their experiments by suspending two panels of Eastern pine in Gloucester Harbour, Massachusetts from May 2021 to March 2022. They took the panels, now colonized by Teredo navalis larvae, back to the lab and hung them in simple aerated 1.6-L salt-water aquaria.
Teredo navalis grow quickly (1.5–2 mm per day compared to blue mussels’ 0.1–0.2 mm per day) so they were harvestable at 9 months, compared to 2 years for blue mussels.
The simple system produced healthy naked clams with an excellent nutritional profile. Naked clams were high in protein, mono-unsaturated fatty acids, and vitamin B12. The high B12 content is especially important because no plants produce B12; it is found only in animal-source foods such as meat, milk, and eggs. As diets trend toward plant-based foods, more sources of B12 will be needed. Compared to blue mussels, the naked clams had almost twice the B12 content, at 140 µg per 100 g dry weight.
The research team also tried supplementing the naked clams’ diet with algal microcapsules—dried algae wrapped in tiny waxy bubbles, <50 µm in diameter—which increased their concentrations of polyunsaturated fatty acids such as EPA and DHA, essential for nerve function and brain health.
At the same time, the team was answering some very basic questions about naked clam biology. Teredinid worms have not been intensively studied, and it was not known whether their main source of nutrition was filter feeding or wood consumption. This study has answered that at last: they can survive on wood alone, but filter feeding is an important component of their diet when available.
Naked clam aquaculture represents a new way to convert wood, even waste wood, into a nutritious source of protein with a low carbon footprint. Next steps in developing naked clams as a sustainable food source could include optimizing the aquaculture conditions, like finding out which types of wood they prefer, and fine-tuning the algae supplements. This simple system could be implemented anywhere, because it requires just water and wood. Perhaps naked clams will be coming to a table near you in the not-too-distant future.