Induction of sexual behavior in male fish (Rhodeus ocellatus ocellatus) by amino acids.

A new function of amino acid in fish behavior was found. Amino acids induced sexual behavior in male rose bitterling (Rhodeus ocellatus ocellatus). Two types of sexual behavior which were pecking and sperm release were observed. Amino acids are known as feeding stimulants in some fish. The pecking behavior of male fish induced by amino acids is similar to the feeding behavior but it was sexual. Only male bitterling showed pecking and sperm release but the female showed no response to the amino acids. 10 out of 20 amino acids induced sexual behavior and both pecking and sperm release were induced by the same amino acids. These two kinds of behavior changed alternately depending on the light conditions. It is of interest that non-specific material such as some amino acids function like sex pheromone.