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Structure and function of sea lamprey pheromone components (Phase II)

Pheromones are essential for a sea lamprey to complete its life cycle, and thus are potential targets for sea lamprey control. It is well established that larval sea lamprey release a migratory pheromone that guides migratory adults to a suitable spawning ground where mature males release a mating pheromone that attracts mature females to their nests. We recently found nesting mature males also likely release a novel territorial pheromone that repels other mature males from entering nest boundaries. These pheromones comprise multiple components and induce highly predictable behaviors. The main component of the male mating pheromone has been identified, whereas identities of other suspected pheromone components have remained elusive. In our field studies, complete pheromones containing all pheromone components (such as washings of larvae or mature males) are shown to be more effective in modifying lamprey behaviors than individual components. Over the last three years (Phase I of this proposed study), we have identified several novel steroid sulfates from the washings of mature males as well as numerous stereoisomers of novel tetrahydrofuran-diol lipids from the washings of larvae. All of these compounds showed acute olfactory potency and several influenced the locomotion and distribution of adult sea lamprey in manners consistent with the function of migratory, mating, or territorial pheromones. Furthermore, chemical, electro-physiological and behavioral analyses indicate that numerous compounds of similar structures from the olfactory and behaviorally active fractions remain to be identified. These data support a hypothesis that tetrahydrofuran-diol lipids compose the larval migratory pheromone, whereas sulfated steroids compose male mating and territorial pheromones. Our overarching objective is to characterize the structures and functions of all these candidate pheromone components. We expect to identify numerous novel pheromone compounds from sea lamprey, to define behavioral mechanisms of the larval migratory, the male mating and the male territorial pheromones, and to establish a pipeline of candidate compounds for field studies of pheromone application in the integrated lamprey management. 

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