Direct behavioral evidence that unique bile acids released by larval sea lamprey (Petromyzon marinus) function as a migratory pheromone
Summary
Four behavioral experiments conducted in both the laboratory and the field provide evidence that adult sea lamprey (Petromyzon marinus) select spawning rivers based on the odor of larvae that they contain and that bile acids released by the larvae are part of this pheromonal odor. First, when tested in a recirculating maze, migratory adult lamprey spent more time in water scented with larvae. However, when fully mature, adults lost their responsiveness to larvae and preferred instead the odor of mature individuals. Second, when tested in a flowing stream, migratory adults swam upstream more actively when the water was scented with larvae. Third, when migratory adults were tested in a laboratory maze containing still water, they exhibited [...]
Summary
Four behavioral experiments conducted in both the laboratory and the field provide evidence that adult sea
lamprey (Petromyzon marinus) select spawning rivers based on the odor of larvae that they contain and that bile acids
released by the larvae are part of this pheromonal odor. First, when tested in a recirculating maze, migratory adult lamprey
spent more time in water scented with larvae. However, when fully mature, adults lost their responsiveness to larvae
and preferred instead the odor of mature individuals. Second, when tested in a flowing stream, migratory adults
swam upstream more actively when the water was scented with larvae. Third, when migratory adults were tested in a
laboratory maze containing still water, they exhibited enhanced swimming activity in the presence of a 0.1 nM concentration
of the two unique bile acids released by larvae and detected by adult lamprey. Fourth, when adults were exposed
to this bile acid mixture within flowing waters, they actively swam into it. Taken together, these data suggest
that adult lamprey use a bile acid based larval pheromone to help them locate spawning rivers and that responsiveness
to this cue is influenced by current flow, maturity, and time of day. Although the precise identity and function of the
larval pheromone remain to be fully elucidated, we believe that this cue will ultimately prove useful as an attractant in
sea lamprey control.
