Mixture of new sulfated steroids functions as a migratory pheromone in the sea lamprey.

The sea lamprey is an ancient, parasitic fish that invaded the Great Lakes a century ago, where it triggered the collapse of many fisheries. Like many fishes, this species relies on chemical cues to mediate key aspects of its life, including migration and reproduction. Here we report the discovery of a multicomponent steroidal pheromone that is released by stream-dwelling larval lamprey and guides adults to spawning streams. We isolated three compounds with pheromonal activity (in submilligram quantities from 8,000 l of larval holding water) and deduced their structures. The most important compound contains an unprecedented 1-(3-aminopropyl)pyrrolidin-2-one subunit and is related to squalamine, an antibiotic produced by sharks. We verified its structure by chemical synthesis; it attracts adult lamprey at very low (subpicomolar) concentrations. The second component is another new sulfated steroid and the third is petromyzonol sulfate, a known lamprey-specific bile acid derivative. This mixture is the first migratory pheromone identified in a vertebrate and is being investigated for use in lamprey control.

Evidence that petromyzontid lampreys employ a common migratory pheromone that is partially comprised of bile acids.

This study examined whether the larval pheromone employed by adult sea lamprey (Petromyzon marinus) to locate spawning streams and known to be at least partially comprised of bile acids is also employed by other lamprey species. Both production and release of lamprey-specific bile acids, and sensitivity to them were examined in a wide variety of species. High pressure liquid chromatography and electrospray ionization/mass spectrometry (ESI-MS) found gallbladders from 10 species of European and North American lamprey to contain large quantities of petromyzonol sulfate (PS) together with much smaller quantities of allocholic acid (ACA) and petromyzonol (P). Evaluation of holding waters from three of these species using ESI-MS found all to contain large quantities of PS and lesser quantities of ACA in similar ratios. Electro-olfactogram recording from the olfactory systems of three parasitic lamprey species found all to detect PS and ACA with high sensitivity. Behavioral studies using migratory adult sea lamprey found them to be attracted to the odors of heterospecific larvae as well as conspecific larvae, both of which contained similar amounts of PS and ACA. Finally, adult silver lampreys (Ichthyomyzon unicuspis) were also found to be attracted to the odor of larval sea lamprey. Together, these results demonstrate that PS and ACA are commonly produced and released by larval petromyzontid lampreys and likely used as part of a common evolutionarily conserved pheromone. This scenario is reasonable because lampreys share similar larval and spawning habitat requirements, and their larvae derive no apparent benefit from producing compounds that serve as an attractant for adults.