A multi-component migratory pheromone in the sea lamprey

Stream finding by the anadromous sea lamprey is mediated by a pheromone released by stream-resident larvae which functions as an instinctively recognized indicator of habitat suitability. This cue is comprised of multiple components including the bile acid, petromyzonol sulfate, and at least one other as yet unidentified compound with a molecular weight of 704 daltons. These compounds are detected at picomolar concentrations and are released in large quantities; laboratory experiments demonstrate that each stream-resident larva activates at least 400L of water an hour. The actions of this pheromone are synergized by other compounds found in natural stream waters. Field studies demonstrate that the migratory pheromone plays a key role determining adult lamprey distribution in the Great Lakes. The cue does not appear to be species-specific or specialized, but rather a composite of biologically-relevant compounds that migratory adults have evolved the ability to recognize.