WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2025 43 methods to harvest polychaetes from coastal shores (Figure 2). One common practice involves the use of torn fresh fish scattered across the tidal flats to lure the worms. As polychaetes emerge from the sand and bite the fish flesh, the fishermen quickly collect the sandworms with their bare hands. In some areas, Filipino fishermen would use ginamos or fermented fish, washed in water, instead of fresh fish for attracting the polychaetes. Elsewhere, some would dig up the sandy shores to collect bigger worms to use as live baits. Across various regions in the country, locals call them by a variety of names including “himag,” “hipan-hipan,” “sasing” and “ulod-ulod.” Among the many species harvested by Filipino fishermen one stands out, as this was a recently discovered polychaete in a specific region in the country: the “ulod-ulod.” From its discovery in Philippine muddy shores, could these worms, once a local secret, really spark innovation and pave the way toward a more sustainable future in Philippine aquaculture? The Rise of Ulod-Ulod: From Local Secret to Aquaculture Gold In the heart of Iloilo, a newly discovered species of polychaetes named Marphysa iloiloensis has emerged as a game-changer, offering potential for sustainable aquaculture practices in the Philippines. Locally known as “ulod-ulod,” this segmented marine worm belonging to the family Eunicidae, proves to be more than a mere sediment cleaner in the mud but also a resource of immense economic and ecological value (Figure 3). The discovery of M. iloiloensis began with an unexpected observation. In 2017, Mary Anne Mandario, a researcher at the Southeast Asian Fisheries Development Center (SEAFDEC), was conducting experiments on polychaetes when she noticed something unusual. The eggs she had collected and placed in culture tanks exhibited an extraordinary survival rate, ten times higher than expected. Unlike other polychaetes that freely spawn their eggs into the water, M. iloiloensis encases its eggs in protective jelly cocoons. This unique adaptation ensures high larval survival by shielding them from environmental stressors and predators (Glabsy et al. 2019). This discovery eventually led to the classification of Marphysa iloiloensis as a new species, officially recognized in 2019. For centuries, local communities have regarded ulod-ulod as a humble inhabitant of the estuarine mudflats, often overlooked. However, their significance extends far beyond that. In aquaculture, high-quality live feed is essential for improving the health and reproductive performance of farmed shrimp and fish. While imported polychaetes, such as Perinereis nuntia from Thailand, are commonly used in crustacean hatcheries (Francisco 2020), this reliance on international suppliers increases costs and limits accessibility. In contrast, as a native species welladapted to local conditions M. iloiloensis presents a promising alternative for sustainable hatchery operations in the Philippines. The challenge, however, lies in mass production. Since wild-caught polychaetes often carry pathogens due to their role as detritivores, cultivating M. iloiloensis in controlled environments is necessary to ensure their safety as feed. This is precisely what researchers at SEAFDEC have achieved in the past few years, developing reliable culture techniques to harness the full potential of M. iloiloensis for Philippine aquaculture. However, while wild-caught M. iloiloensis tends to show relatively high survival under certain conditions, hatchery-bred individuals face significant challenges in survival and growth consistency (Figure 4) (SEAFDEC Annual Report. 2022). Therefore, there is a need to refine rearing techniques, improve water quality management, and optimize diet formulations to boost survival rates of hatchery-produced polychaetes. Ms. Mandario (2020) has shown that specific culture techniques and diet (CONTINUED ON PAGE 44) FIGURE 3. Marphysa iloiloensis harvested from the grow-out tanks. This species is characterized by its soft body and reddish-brown coloration. Photo credit: R. Jabines. FIGURE 4. Survival rate comparison of wild-caught and hatchery-bred polychaetes. Photo credit: R. Jabines.
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