From the side and hellish from below, the lamprey is the lane of the Great Lakes fishing industry. The lamprey is a cockless, blood-sucking fish and is often considered an early vertebrate because of its rudimentary morphology and the life stage of larvae. Now a team of researchers has written a new study on petrified lamprey larvae from the Devonian period, which they say shows that lamprey evolution took place differently from what was previously thought. That would mean we would have to change our story of vertebrate origin.
The researchers’ paper was published Wednesday in the journal Nature. Their argument depends on the life cycle of lamprey. Modern lampreyl larvae, called ammocoetes, are blind filter feeders, which later turn into their distressed, predatory adults. Biologists and paleontologists have seen the larval stage of the ammo cot as a remnant of the early evolution of vertebrates, and a sign that lamprey can be relied upon as a living fossil that helps explain where all animals with backpacks come from. But the recent team describes baby lamprey fossils that are not ammo cots – these fossils look just like smaller versions of adult lamp trips – suggest that the larval stage was a later evolutionary adaptation, unique to lamp trips.
“Now, it seems like the lamp journeys are the strange ones,” Tetsuto Miyashita, a paleontologist at the Canadian Museum of Nature and lead author of the article, said in a video call. ‘[The lamprey] looks primitive, more primitive than these extinct cockless fish. But it was the other way around. ”
Miyashita’s team describes four different types of antique lamprey from Africa and North America, ranging from 360 to 310 million years old. At the time, the areas in Montana, Illinois and South Africa (where the eel-like lamps were excavated) were shallow seas; a different habitat than the freshwater that most lamprey wraps today.
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The non-ammocoete fossil lamprey was not a smaller group of adult lampreys, the team says, as some of the fossilized fish even have yolk sacs that are still attached to their bodies. If it was just in one place, ‘we would have thought we were looking at this strange, specialized, extinct lamprey lineage that did its own thing and perhaps lost the filter-feeding larval phase,’ Miyashita said. “But species after species after species, in four different generations of fossil lamps, they show the same thing.”
The authors suggest that the ammocoete larval stage was an adaptation that the lamprey developed to move into the freshwater environments in which they now thrive all too well. During the 20th century, numerous attempts were made to invasive lamprey population in the Great Lakes. The lampreys, first observed in Lake Ontario in 1835, spread to the other large lakes in the mid-20th century. Now the established population is wreaking havoc on the trout, whitefish, cookies and other fish species of the lakes, holding them with their suckers and eventually killing them. By the 1960s, the annual catch of the Great Lakes was 2% of the previous average; a dramatic nose dive attributed to the lampreys.
“These species, such as lamprey, which we consider ‘old fish’, develop as long as we have and are not frozen in time,” said Jera.miah Smith, a biologist at the University of Kentucky who was not affiliated with the recent paper, in an email. “More broadly, the study clearly shows that it is important to consider alternatives to generally accepted evolutionary scenarios, and how new datasets continue our understanding of the deep evolutionary history of the vertebrate generation.”
For an alternative candidate for a vertebrate ancestor, the researchers suggest that the armored Devonian fish, called ostracoderms, look a lot like frogfish going to war.
“Lampreys are not quite the swimming time capsules we ever thought of,” co-author Michael Coates, a biologist at the University of Chicago, told a Canadian Natural History Museum. Press release. “They remain important and essential for understanding the deep history of vertebrate diversity, but we must also realize that they too have developed and specialized in their own right.”
This story has been updated to include comments from Jeramiah Smith.