Naked Clams to open a new sector in sustainable nutritious food production

The UN highlights the urgent need for drastic changes in land use, agriculture, and diets to mitigate climate change. 'Blue Foods' from aquatic and marine environments are a vital part of this solution, offering nutrient-rich profiles with lower environmental footprints compared to terrestrial meats. Bivalve aquaculture, a growing sector, promises efficient production, reduced costs, and improved sustainability. Bivalves like mussels and clams are rich in protein, essential fatty acids, and micronutrients, yet conventional bivalve farming faces challenges. These include habitat degradation, food safety concerns due to pollution, slow growth rates affecting profitability, and weak consumer demand. Teredinids (shipworms), a largely understudied group of bivalves, could offer a solution. They are remarkably fast-growing, with some species growing up to 1.5-2 mm per day, significantly faster than conventional bivalves. Uniquely, they live in and feed on wood, requiring only small shells, hence the name 'Naked Clams' proposed in this study to improve marketability. This wood-boring nature has a historical precedent of sustainable, low-impact food production by Australian Aboriginals. Naked Clam aquaculture offers potential for rapid, sustainable production of nutrient-rich bivalve meat, effectively transforming sustainably-grown wood into human food, supporting a circular economy. This system could be efficient and reduce processing costs, and have the capacity to be established near consumers, other coastal industries, or even in modular systems (e.g., shipping containers). The potential economic opportunity is substantial. However, scaled Naked Clam aquaculture remains uncharted territory. A crucial step is understanding their optimal growth and feeding strategies in aquaculture, as well as their nutritional profile. While Naked Clams are consumed and praised in Southeast Asia, their nutritional profile lacks formal scientific analysis. This study aimed to establish a research foundation for Naked Clam aquaculture, demonstrating a modular system, assessing feeding efficacy under various diets (including microencapsulated feeds for fortification), and providing the first detailed nutritional profile, including fatty acid composition, vitamin B₁₂, carbohydrates, fats, and protein content. This involved novel methodologies for vitamin B₁₂ and lipid analysis.

Existing literature highlights the global need for sustainable and nutritious food sources to address food security and climate change concerns. Studies emphasize the potential of blue foods, particularly bivalves, but also the limitations of current bivalve aquaculture practices, including slow growth rates, environmental impact, and consumer perception. While teredinids have been traditionally harvested and consumed in some regions, their aquaculture potential has been largely unexplored, with limited scientific research available on their growth, feeding strategies and nutritional profile.

This study involved three key phases: establishing a pilot aquaculture system, evaluating feeding efficacy under different dietary regimes, and performing a detailed nutritional analysis. **Sample Collection:** *Teredo navalis* specimens were collected from northeast US coastal waters using Eastern pine panels deployed in Gloucester Harbor, MA, USA. Blue mussels (*Mytilus edulis*) were obtained from commercial farms in Shetland, Scotland, and served as comparison. **Microencapsulated Feed:** Lipid-walled microcapsules containing *Schizochytrium* algae were manufactured by BioBullets Ltd. These had a mean diameter of 46.6 µm and were designed for bivalve consumption. **Laboratory Conditions:** Experiments were conducted in aerated, temperature-controlled tanks (15 °C) at the University of Plymouth. **Feed Assimilation Efficacy:** This assessed the assimilation of three diets: wood only, wood + microcapsules, and wood + Shellfish Diet 1800 (a commercial algal feed). Faecal production (weight, rate, and output) was measured using GoPro cameras for daily recording, and visual counts and weighing of the faecal pellets collected weekly to determine assimilation efficiency. SEM-EDS analysis was used to examine the composition of faecal material from different diets. **Nutritional Profiling:** The study conducted the first formal nutritional analysis of *T. navalis*. Biochemical composition (proteins, carbohydrates, and lipids) was determined using FTIR-ATR spectroscopy. Vitamin B₁₂ content was measured using a microbiological bioassay with a B₁₂-dependent strain of *Chlamydomonas reinhardtii*. Lipid analysis involved trans-esterification of freeze-dried tissues and analysis by GC to identify fatty acid methyl esters (FAMEs). **Statistical Analysis:** One-way ANOVA and post-hoc tests (Tukey's HSD or Tukey-Kramer) were used to compare differences between dietary regimes and species for feed assimilation efficacy and nutritional parameters.

The study successfully piloted a modular Naked Clam aquaculture system (Fig. 1) consisting of wooden panels in aerated aquaria, which effectively supported Naked Clam growth. Feeding efficacy studies (Fig. 2) showed significantly higher faecal pellet weight in clams fed wood + microcapsules compared to wood-only or wood + Shellfish Diet 1800, indicating greater nutrient retention. The faecal production rate was significantly lower for the microcapsule diet, suggesting a longer gut retention time for these microcapsules compared to the liquid feed (Shellfish Diet 1800) (Fig. 2). SEM-EDS analysis (Fig. 3) showed compositional differences in faeces: wood-only faeces showed uniform wood fragments, while microcapsule-supplemented faeces were clumpier and contained significantly more calcium. The first nutritional profile of Naked Clams (Fig. 4) revealed a high protein content (22.5-29% DW), comparable to blue mussels. Naked Clams had significantly higher vitamin B₁₂ content (142 ± 9 µg/100g DW) than blue mussels (81 ± 9 µg/100g DW) (Fig. 4). Microcapsule supplementation significantly increased protein content but did not affect B₁₂ levels. Fatty acid analysis (Fig. 5) showed that Naked Clams contained more long-chain saturated fatty acids than blue mussels. Microcapsule supplementation significantly increased levels of essential PUFAs EPA and DHA (Fig. 5). The dominant FAMEs in Naked Clams were stearic acid (C18:0) and palmitic acid (C16:0), followed by oleic acid (C18:1) and palmitoleic acid (C16:1). Supplementing with microcapsules increased the polyunsaturated acid content (Fig. 5).

This study successfully demonstrated a functional pilot system for Naked Clam aquaculture and highlighted their inherent nutritional richness, particularly in vitamin B₁₂ and monounsaturated fats. The findings also showed the potential to enhance their nutritional profile by using supplemental microencapsulated feeds, especially in terms of increasing essential PUFAs (EPA and DHA). The significant difference in faecal pellet weight and rate between dietary regimes suggests that the microcapsules are efficiently digested and nutrients absorbed. This contradicts some previous literature, suggesting wood is the primary food source of *T. navalis*, and demonstrates that filter-feeding, even with supplements, does not significantly alter the assimilation rate. The high levels of vitamin B₁₂ and oleic acid in Naked Clams are particularly noteworthy, offering significant health benefits. The ability to fortify Naked Clams with PUFAs further enhances their nutritional value, providing a potentially sustainable alternative to fish as a source of these essential fatty acids. These findings support the development of a new aquaculture sector based on Naked Clams, offering a sustainable and environmentally friendly way to produce nutrient-rich food.

This research provides a strong foundation for developing Naked Clam aquaculture as a sustainable food production system. The pilot system proved effective, and feeding efficacy studies demonstrated the potential for nutritional enhancement. The naturally high levels of vitamin B₁₂, monounsaturated fats, and the possibility of enriching PUFAs make Naked Clams a promising food source. Future research should focus on optimizing growth conditions, feed formulations, and scaling up production for commercial viability. Furthermore, developing effective strategies for consumer engagement and market penetration is crucial for the success of Naked Clam aquaculture.

The study used a limited number of Naked Clam individuals and dietary regimes. Further research with larger sample sizes and a wider range of feed types is needed to confirm the findings. The study focused on one species (*Teredo navalis*), while other teredinid species may exhibit different growth and nutritional characteristics. More detailed analysis of nutrient absorption and the impact of different wood species could also be explored. Finally, long-term studies are needed to evaluate the sustainability and scalability of Naked Clam aquaculture in commercial settings.