The Nose Knows: Odor Response of Pacific Lamprey (Entosphenus tridentatus)

Methods to recover imperiled lamprey populations could include using odors to attract or repel migrating or spawning adults. Using Pacific lamprey (Entosphenus tridentatus) in a two-choice maze, we conducted  preliminary experiments to evaluate the response of adult females to introduced odors. First, we evaluated the reaction of pre-ovulatory females to odor from tanks containing pre-spawning conspecifics (males and females). We also tested whether ovulatory females were attracted to a synthesized, male sex pheromone (3kPZS) that was based on a natural sea Lamprey (Petromyzon marinus) template. In all tests, the pre-ovulatory lamprey showed consistent nocturnal activity patterns, typically moving from sunset until sunrise and remaining inactive during daylight hours. The number of entries and the amount of time pre-ovulatory females spent in treatment and control arms of the maze was not significantly different (P>0.89). Ovulatory females also showed no difference in the number of entries into the arm receiving synthesized 3kPZS (P=0.19). Unexpectedly, they spent significantly less time in the arm containing the synthesized sex pheromone (P=0.04) than in the adjacent control arm. These data hint that odor recognition is species-specific. Further testing is needed to confirm that adult females are not attracted to odors produced by conspecifics throughout reproductive development.