A releaser pheromone that attracts methyltestosterone-treated immature fish in the urine of ovulated female rainbow trout

Behavioral experiments concerning a releaser pheromone in the urine of fema le rainbow trout were performed using immature fish administered orally wit h 17 alpha -methyltestosterone (MT) during the non-spawning season. The uri ne was collected by catheter. The frequency of entries of test fish was rec orded in each channel scented by test and control solutions in a Y-maze tro ugh. The behavior of both MT-treated and control fish demonstrated that the y could not discriminate the differences between distilled and environmenta l water as control solutions. There was also no difference between MT-treat ed and control fish when distilled and environmental water were introduced. The MT-treated immature fish were attracted to the channel scented by ovul ated female urine. Neither coelomic fluid nor the immature female urine had any effect on the behavioral responses of MT-treated fish, while immature control fish had no preference for the urine of ovulated females. These res ults suggest in rainbow trout that ovulated female urine contains a release r pheromone to attract mature males, and that androgens are involved in the sensory mechanisms detecting the releaser pheromone in fish.