Abstract
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.
