Masters of Perfumery: Synthesis and Release of Pheromones in Sea Lamprey

The sea lamprey (Petromyzon marinus L.), a jawless parasitic fish that represents the most basal lineage of vertebrates, has evolved a dependency upon sex pheromones to synchronize a single reproductive season and successfully spawn. The potent odors (mainly bile salts) are released by mature males, serve as an attractive signal to ovulated females, and indicate that the male sender is ready for courtship. We hypothesize that an animal with such reliance upon pheromonal bile salts for reproduction must have evolved an equally reliant mechanism of synthesis and release of these cholesterol-derived compounds. Here, we show that specific genes associated with synthesis and releases of a sex pheromone are dramatically upregulated upon sexual maturation. We elucidate key aspects of the synthetic pathway of pheromonal bile salts across tissues, and examine environmental and physical factors that influence the release rates of these compounds. Sea lamprey provide a well characterized example of bile salt synthesis and excretion that appears to have evolved for an additional function of bile salts as a sex pheromone.