SEAFDEC/AQD Southeast Asian Fisheries Development Center | Aquaculture Department
Most people would not expect a scientific breakthrough to emerge from pond mud. But in 2017, a routine culture experiment at SEAFDEC/AQD in Iloilo took an unexpected turn.
Then researcher Dr. Mary Anne Mandario stocked culture tanks with jelly cocoons, the egg capsules of mudworms, and expected little more than another round of observations.
Instead, the worms multiplied far beyond what Dr. Mandario (now a scientist as of this writing) expected.
The dramatic increase caught her attention. More intriguing, however, was the appearance of two distinct polychaete species. One appeared familiar. The other did not resemble any species she could identify.
Rather than dismissing the anomaly, Dr. Mandario pursued it.
Specimens were sent to Dr. Christopher Glasby, a polychaete taxonomist at the Museum and Art Gallery of the Northern Territory in Australia, for detailed morphological and molecular analyses. The results confirmed that one worm belonged to the family Nereididae. The other represented a species previously unknown to science.
In 2019, Dr. Mandario and five co-authors formally described the new species in Zootaxa. It was subsequently listed in the World Register of Marine Species as Marphysa iloiloensis, named after Iloilo, where the specimens had been collected.
For many scientists, discovering a new species would be the culmination of years of research.
For Dr. Mandario and her colleagues, it marked the beginning of a much bigger story.
As researchers continued studying M. iloiloensis, they discovered that the worm possessed characteristics that could help address long-standing challenges in shrimp aquaculture.
More than just a marine worm
Shrimp hatcheries have long depended on live marine worms to feed broodstock because they provide the protein, lipids, and essential fatty acids needed for ovarian maturation and egg production. Artificial feeds alone often cannot supply all of these nutritional requirements.
For decades, many hatcheries have relied on wild-caught polychaetes collected from estuaries and mudflats. While nutritionally effective, harvesting wild worms disturbs coastal habitats and increases the risk of introducing pathogenic bacteria, parasites, and viruses into hatchery systems.
- iloiloensis offered a promising alternative.
Unlike many commonly harvested polychaetes that spawn only once before dying, M. iloiloensis, a member of the family Eunicidae, reproduces repeatedly throughout its lifetime. In captivity, the worms reach sexual maturity within four to five months and can spawn multiple times from the same breeding population, making continuous culture possible.
The species also proved to have high nutritional value. During a 180-day grow-out trial, worms raised on bioflocs and feed mill sweepings contained about 64 percent protein and 13 percent fat—nutrient levels suitable for shrimp broodstock maturation.
Cleaning ponds from the bottom up
The potential of M. iloiloensis extends beyond its value as live feed.
Aquaculture ponds naturally accumulate uneaten feed, shrimp feces, and other organic wastes. As these materials settle, they can reduce oxygen levels in the sediment, contribute to unstable water quality, and increase ammonia concentrations.
Dr. Mandario found that M. iloiloensis helps address these problems through bioturbation. As the worms burrow through the pond bottom, they consume organic detritus, loosen compacted soil, redistribute nutrients, and improve oxygen movement. Their activity accelerates decomposition and reduces the buildup of organic matter.
Experimental systems containing M. iloiloensis showed cleaner sediments and lower organic loading, suggesting that the species could improve pond health while also serving as a nutritious live feed.
From discovery to innovation
The discovery of M. iloiloensis eventually led beyond species identification.
In March 2020, SEAFDEC/AQD filed a patent application with the Intellectual Property Office of the Philippines for a larval rearing method developed for the species. Granted in 2023, the patent describes a culture system that uses fresh bioflocs as both food and settlement substrate, allowing high larval survival under controlled conditions. SEAFDEC/AQD holds the patent, with Dr. Mandario named as the sole inventor.
Researchers continue refining large-scale production methods while evaluating the worm’s broader use in commercial hatcheries. Standardized culture protocols, disease management strategies, and distribution systems remain necessary before the species can be widely adopted by the aquaculture industry.
What began as an unexpected increase in worms inside a culture tank has since become a promising line of research. From improving shrimp broodstock nutrition to enhancing pond sediment quality, Marphysa iloiloensis demonstrates how careful observation can transform an overlooked organism into a practical solution for aquaculture.
