The present investigation was conducted to identify the feeding stimulants for juvenile ell Anguila japonica using a synthetic extract, based on the composition of the marine worm Perinereis brevicirrus. Juvenile eel showed a marked preference for a diet flavoured with the synthetic extract over an unflavoured diet.
Feeding preference tests for the diet flavoured with one of the three major fractions (amino acids, uncleotides and other compounds) in the extract showed that the amino acids fraction was most stimulatory, followed by the “other compounds” fraction including glycine betaine and maltose, while the uncleotides fraction including adenosine-5'-monophosphate was inactive or repellent. The active constitunet in the amino acids fraction was identified as the fraction glycine, alanine, proline plus histidine whose activity fraction was mixed with uridine-5'-monophosphate, the resulting mixture was found to be more stimulatory than the amino acids fraction or the complete synthetic extract.