Sexually mature male goldfish release large quantities of androstenedione into the water where it functions as a pheromone

Previous studies have demonstrated that ovulatory female goldfish release a variety of sex steroids into the water where they function as a pheromonal blend dominated by C₂₁ steroids that stimulates male hormone release, sperm production and behavior. This study investigated whether male goldfish might also release sex steroids with pheromonal activity. It found that spermiated male goldfish release substantial quantities of androstenedione (AD; about 50 ng/h) together with smaller (10-20 ng/h) quantities of several other related C₁₉ steroids but only very small quantities (<5 ng/h) of C₂₁ steroids. Further, when sexually aroused by females and/or their pheromones, males released even greater quantities of AD (up to 1 μg/h) while C₂₁ steroid release rate changed little. This created a ratio of C₁₉ to C₂₁ steroids of about 50:1 that was dramatically different from that emitted by females (1:7). The male olfactory system was also found to be extremely sensitive to AD, detecting it to near picomolar concentrations. Together with previous studies that have shown water-borne AD to increase male aggressive behavior while suppressing responsiveness to female pheromones, this study establishes AD as a male pheromone in the goldfish. Because ovulating females also release AD but in the presence of C₂₁ steroids, recognition of the male-derived steroid pheromone is presumably mixture dependent. Crown copyright