How to beat the sea lamprey with its own pheromones, bile salts
Researchers are now closer to using the invasive species's predilection for bile salts against it.
What could be more seductive than bile salts? Well, for a sea lamprey, bile salts are about as good a come-on as come-ons come.Skip to next paragraph
In Pictures The most bizarre creatures of the deep
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The sea lamprey, an invasive and destructive species in the Great Lakes, has evolved to use bile salts, acids brewed in their livers to assist in digestion, as pheromones. That's right: female sea lampreys are so enthusiastic about digestive aids that they'll squiggle upstream in pursuit of the enticing males producing them.
It’s an unusual preference — so unusual, new research shows, that not even the silver lamprey, a cousin to the sea lamprey but a native to the lakes, shares the sea lamprey's predilection. That’s a find that could help researchers develop traps that use the sea lamprey’s affinity for bile salts against it, while sparing the native lamprey species.
Understanding how the two species respond to bile salts is “very interesting when developing a pheromone program for sea lamprey control,” said Tyler Buchinger, a graduate student at the Michigan State University and an author on the paper, in an email to the Monitor.
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“This research provides necessary data on the effect of sea lamprey pheromones on closely related non-target species,” he says. The findings are published in Proceedings of the Royal Society B.
Sea lampreys belong to an ancient order of eel-like fish, most of which, including the sea lamprey, are parasites on other fish. Sea lampreys’ gory lives begin as larvae hatched from fertilized eggs. Three to six years later, these larvae swim downstream toward the Great Lakes, smooching their mouths on unfortunate fish and sinking their rows of teeth into their flesh (skip the $13 admission price to a horror movie and pull up a photo of a sea lamprey’s jawless, circular mouth instead – you won’t be disappointed). Once attached, the parasites will then suck out the unfortunate fish’s bodily fluids.
If the fish is large, it will survive the encounter, with a bullseye scar to boot. If it is small, it will die, and the sea lamprey will snuggle up to another victim with its toothy kiss. After about a year of feeding, sea lampreys detach themselves to swim upstream, breed, and die.
There are five native lamprey species in the Great Lakes, but sea lampreys are not among them. Instead, these interlopers are believed to have arrived from the Atlantic via the new canals connecting North America’s water bodies in the early 1900s. The first invading sea lamprey was fished from Lake Erie in 1921. Over the next decade, the invader was spotted in each of the other four Great Lakes, ending its conquest with Lake Superior in 1938.
The sea lamprey's arrival was not welcome. Profiting from the invader’s advantage in an ecosystem unprepared to deal with it, the sea lamprey fed with abandon, bleeding out rainbow trout, lake trout, salmon, whitefish, and catfish, among others. As it fed, local fisheries – an industry now valued at about $7 billion – began to buckle.