The Scent of Lamprey Love

November 3, 2022
By Science and the Sea staff

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Female lampreys use odor receptors in their nose to detect the pheromone spermine contained in the semen of male lampreys. Credit: Dave Herasimtschuk, US Fish & Wildlife Service.

A key aspect of sexual attraction for many animals is the involvement
of pheromones—chemicals secreted by an animal that other members
of that species respond to. It’s no different for lampreys, an eel-shaped
parasitic fish with a formidable suction-cup mouth. For these creatures,
what attracts female lampreys to potential mates is the enticing smell of
sperm. A compound called spermine is present in the semen of a wide
range of animals, including humans, but scientists have only recently
discovered that spermine is a strong aphrodisiac for female lampreys
that are ready to mate.

Scientists have already been replicating pheromone odors that attract
lampreys and using it to improve their population-control methods, and
now spermine can become another tool in their toolbox. The research
required testing nearly 12,000 pairs of chemicals against lamprey odor
receptors to discover the pair that matched. Researchers learned that
female lampreys use spermine to pick the best mates living near the
gravel beds in streams, where they can spawn several times an hour.

The discovery has led to new strategies for controlling sea lampreys
in the Great Lakes, where they’ve become a particularly destructive
invasive species over the past century and a half. Though native to the
Atlantic Ocean, sea lampreys made their way to the Great Lakes in the
1830s and have been tearing away the flesh of lake fish and sucking
out their insides ever since. Each lamprey consumes an estimated 40
pounds of fish every year. U.S. and Canadian regulatory agencies have
worked together to reduce the impact of lampreys in the region using
barriers, traps, and lampricides—chemicals that are deadly to lamprey
larvae but harmless to other animals—in streams that flow into the
lakes.