Sea lampreys sniff out sexy pheromones

Male sea lampreys release a chemical to attract their mates, scientists have found. The discovery could help control populations of the parasitic animal that can kill up to 85 per cent of the fish they attack.

Sea lampreys wear two hats. The aquatic vertebrates are destroying sport fish populations in some areas, but in other places, the animals are considered a delicacy and scientists want to boost their populations.

Sea lampreys are native to the Atlantic Ocean and it's thought they made their into the Great Lakes through shipping channels, where they can latch on to popular fish such as salmon and trout. The animals use their sucking disk and sharp teeth to suck the body fluids out of fish.

Scientists didn't know much about whether fish used pheromones to communicate over long distances. It was presumed that females were mostly the ones releasing the chemical come-on.

In the April 5 issue of the journal Science, Michigan State University Fisheries Prof. Weiming Li and his colleagues report a new way of isolating the chemical male sea lampreys produce to lure females.

To find out, the researchers spent two years condensing a ton of water into about 30 milligrams of purified sea lamprey cologne.

After finding the key chemicals, lampreys sniffed the compounds and the researchers tracked the animals' neurological and behavioural responses.

Li's team found the males make the pheromone in their liver and deliver it through their gills to court females. He said females could also be sending out chemicals to signal their fertility and to keep the males closer to home.

The researchers know lamprey can send the pheromone signal far downstream. Their next step will be to find out more about the chemical's potency and effective distance.