Self-cloning salamanders?

NMU student discovers unusual form of amphibian

This is a polyploid blue-spotted salamander. Northern Michigan University ecology student Eli Bieri used a pink visual implant elastomer tag, which involves the injection of dye. The tag is fluorescent, meaning it will show up under a black-light. (Photo courtesy of Eli Bieri)

MARQUETTE — There’s an unusual creature right in our midst, although the vast majority of Marquette residents don’t know it.

Eli Bieri, a Northern Michigan University senior majoring in ecology, has discovered rare forms of the blue-spotted salamander on Presque Isle called polyploids.

He would be the one to make this discovery. Bieri led a 2019 study of salamander fatalities on Peter White Drive at Presque Isle Park. Eventually the city of Marquette Parks and Recreation Department restricted road access in that area during the spring. The Superior Watershed Partnership, located near the salamander crossing, proposed closing Peter White Drive from 6 p.m. to 6 a.m. April 1-May 15 this year, but the COVID-19 pandemic resulted in the road being closed altogether.

The closure seemed to have worked; the SWP reported only three recorded salamander fatalities earlier.

However, Bieri has continued his interest in salamanders, and made a particularly unusual observation in one of his studies in 2019 on Presque Isle.

“I’ve noticed that some of the salamanders looked a little unusual,” Bieri said. “We’re talking, like, twice the size that the normal blue-spotted salamanders are. Then these ones had a lot less pattern. They didn’t really have the blue spots, and they were a faded gray color, which is really unusual and not like any of the salamanders we’re supposed to have in the U.P.”

He also has noticed the polyploid salamanders migrate later in the spring than the regular blue-spotted salamanders; in the case of Presque Isle, it’s across Peter White Drive.

The following spring, he noticed more of these salamanders, which are all females.

Bieri said a diploid animal has two sets of chromosomes — one from each parent. A polyploid animal, on the hand, can have multiple sets.

Wanting to know more, he reached out to Robert Denton, Ph.D., an amphibian geneticist in the Division of Science and Math at the University of Minnesota-Morris, about this polyploid find.

In September, the results came back: The Presque Isle salamanders were indeed of the polyploid kind. Denton also is performing breeding studies with the salamanders Bieri sent.

“Eli’s findings are important because we still don’t know that much about these unique salamanders,” Denton said in an email. “Members of this all-female group don’t really look different than other salamander species, but their DNA tells a completely different story: They’ve been around for millions of years without any males.

“We now know that these animals mostly reproduce clonally but can occasionally ‘steal’ reproductive material from other male salamanders, making them a strange collection of DNA from different species while still maintaining their all-female independence.”

Because they can’t really be differentiated by eye and they are hidden for most of the year, there are likely many places in North America where these salamanders live but go unidentified, Denton said. Bieri’s observations are the first records from the Upper Peninsula.

The polyploid salamanders definitely are unique.

“They can hybridize with others species, but if they don’t want to reproduce sexually, they can clone themselves,” Bieri said.

Of course, there’s a lengthy term for this ability: facultative parthenogenesis. Bieri said they even can reproduce sexually with members of a different species, and can incorporate DNA from other species into their own genome.

“It really throws a wrench in what most biologists consider a species to be,” Bieri noted. “They get the benefits of asexual and sexual reproduction, making them a fascinating model to study different modes of reproduction in vertebrates.”

Bieri said a disadvantage is that these animals lose genetic diversity in any potential mutations that natural selection could act upon.

“You’re literally just copying yourself, so if there’s anything wrong with you, your offspring are going to inherit that too,” Bieri said. “But the great thing for them is that then they have the option and the advantage of sexual reproduction also. It’s a really mind-bending phenomenon.”

As the only known polyploid salamander population in the U.P., the salamanders’ presence at Presque Isle emphasizes the importance of protecting that habitat and mitigating mortality from cars during the spring breeding migration, he said.

One question is: With what species have the Presque Isle polyploids hybridized in the past?

“Now we’re waiting on more genetic tests to actually find out,” Bieri said.

Bieri said he wants to return to the area in the spring and determine the proportion of polyploid salamanders to the regular ones. His current estimate is 10%.

He noted the plan for now is for the city to close off a portion of Peter White Drive in the spring, but there’s also talk of building “ecopasses,” depending on funding. In this method, a drift-net fence and a slope would work together to guide salamanders to a tunnel under the road, keeping them off the road.

“That would be a long-term solution where we don’t have to ever shut the road down,” Bieri said. “No one has to drag a sign.”

Right now, the Presque Isle salamanders probably are starting to overwinter and enter a state of brumation.

“That’s basically the amphibian equivalent of hibernating,” he said. “Their heart rates all slow down, and they’ve been found below 8 feet. They’re so small, people are surprised they can dig at all, but they find little pockets along the tree roots and stuff.”

After graduating from NMU, Bieri is considering entering a master’s program at the University of New South Wales in Sydney, Australia — where amphibians exist.

They’ve been a long-term subject of interest for Bieri.

“Amphibians, in general, I’ve always been drawn to just because they spend half their life in the water, and I’ve always been drawn to the water myself and spent a lot of time in lakes in Michigan as a surfer,” Bieri said.

He also believes they have scientific research value.

“They’re just a great model so we can better understand what asexual reproduction looks like in invertebrates just because it’s so poorly understood,” Bieri said.


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