Nitrogen budget of polychaete Perinereis nuntia vallata fed on the feces of Japanese flounder

The nitrogen budget of polychaete Perinereis nuntia vallata fed on Japanese flounder feces was estimated at 20°C. Worms of 0.2-0.6 g body weight ingested 4.9-25.7mg/individual per day of flounder feces and excreted 1.2-5.5 mg/individual per day (dry weight) of fecal pellets corresponding to 12.2-44.1% (mean 22.4%) of fed flounder feces. Mean ammonia excretion rate of the worms fed the feces was 0.1 mg/individual per day. Based on the ingestion and excretion data and nitrogen content of flounder feces, worm fecal pellets and worm bodies, it was estimated that the worms assimilate 62.8% of nitrogen intake. In 3 weeks rearing with the flounder feces, commercial diets for flounder and polychaetes, and nitrogen assimilation rates for the worms were 46.3%, 47.4% and 53.7%, respectively. From these results, about half of the nitrogen ingested by the worms is converted into worm body tissue.