Abstract
1. Sub-adult guppies were given one or other of three diets (Basal, Chol. I, and Chol. II) that differed in choline contents for a month in freshwater and seawater. 2. The growth of fish fed on the Chol. II diet (Choline 4g/100g) was greater than that of fish fed on the Chol. I diet (Choline 0.5g/100g), and the growth of fish fed on the Basal diet (Choline free) was the lowest. 3. Trimethylamine (TMA) and Trimethylamine Oxide (TMO) concentrations in the muscle or whole body of the fish were determined. The concentrations of TMA and TMO were influenced by the dietary choline level and environmental seawater. Especialy TMO concentrations were markedly higher when fish were fed on Chol. II than Chol. I, and reared in the seawater than in the freshwater. 4. These results suggest that the following conversion system functions in bodies of the guppy: Choline→TMA→TMO
