Looking at them you wouldn’t guess that the unisexual Ambystoma salamanders are different from other members of what was once considered their group.
These intruders were previously grouped with five other species of mole salamanders: the yellow striped tiger salamanders; the blue-spotted salamander, marked as the name suggests; the Brownish Smallmouth Salamander and Jefferson’s Salamander; and the pale riverbank salamander. All five species have flexible, wet bodies, bulbous eyes, and smiling faces.
What defines the mysterious without a name Ambystoma species apart is something that can only be seen by examining their genetics. It’s an all-female lineage and they steal genetic material from the other five species of salamanders in their region, a feat that would seem impossible without the fact that these salamanders have been around for over 5 million years.
âWe are often asked, ‘What is the name of the species for these organisms? “And the answer is we don’t have them because they don’t play by the rules of what we would generally call a species,” said Rob Denton, professor of biology at Marian University. Denton recently received the National Science Foundation Career Fellowship, a five-year award worth $ 1.1 million that will be used to better understand these strange salamanders.
Until the last few decades, no one had realized that unisexual salamanders were anything unusual.
“For a long time, it was thought that these salamanders were typical hybrids, that is, people thought that a blue-spotted salamander and a Jefferson’s salamander could breed and that the result would be newly hybrid offspring. formed. In fact, however, none of the sex species involved in interbreeding in the wild, âsaid Katy Greenwald, professor of biology at Eastern Michigan University, in an email interview.
This perception of these female salamanders being hybrids changed when scientists began to do genetic analyzes. Some descendants of unisexual salamanders are single clones of their mothers. But others had extra chromosome pairs Besides to the mother’s chromosomes – sometimes three chromosomes, or four or even five, all from different male species.
“If you want a human example, it’s like you have to take a sample of my DNA and it has a set of chromosomes from my mom and dad, but then extra sets from an orangutan, of a chimpanzee and a gorilla, âDenton said.
These very different species of monkeys are approximately how distant all species of mole salamanders are from each other.
Scientists are not entirely sure how these salamanders manage to combine so much divergent genetic material without their offspring having adverse effects. The breeding process is a bit simpler. Male salamanders of all of these species will leave packages of semen around wet areas in the spring. Unisexual females seek out semen, absorb it into their own genitals, which stimulates reproduction. Females can continue to search for packages of sperm and incorporate all of that genetic material into their offspring, or they can create simple clones.
As for females belonging to one of the distinct species, whether they are blue-spotted salamanders or Jefferson’s salamanders, they can not mate with males of different species.
Because the process is believed to be totally unique to this unisexual salamander line, it has been given its own name: kleptogenesis, in which females steal genetic material.
Denton and other scientists are now trying to figure out if this unusual strategy has an impact on the survival of the unisexual Ambystoma salamanders. On the one hand, unisexual species are ecologically dominant and sometimes outnumber sexually reproducing salamanders by two to one or three to one. They also regrow their tissue about 1.5 times faster than their sexual parents, which is helpful in cases of tail or limb loss.
But unisexual eggs have a much higher death rate, which means fewer salamanders survive to adulthood. Scientists have also tested the speed and endurance of salamanders by having them walk on small treadmills, and unisexual salamanders don’t have as much physical endurance. This is essential for a creature who must sometimes walk quickly to access the transient wetlands it needs to mate in the spring.
The even more important question is how unisexual salamanders manage to combine so much genetic material without causing defects in their offspring. While most people are used to thinking of DNA as just the combined genetic material of a mother and father, it’s actually a bit more complicated, Denton said. We have DNA in the nucleus of our cells, nuclear DNA, which combines genes from both parents. But inside the mitochondria (other parts of the cell that make energy) there is a form of DNA that comes only from the mother, called mitochondrial DNA.
âThere are many inherited diseases and problems that arise from poor communication between the mitochondrial and nuclear genomes,â Denton said. âEven small things can lead to problems with metabolic diseases and infertility. These animals can sort of navigate this problem. There’s something about the way they deal with genomic material that allows them to do this, and at the moment we have no idea how.
Better understanding how unisexual salamanders manage to incorporate so much disparate genetic material into their offspring could also help us better understand human biology.
But Denton and Greenwald both emphasized that salamanders deserve full study, regardless of what they might tell us about humans. Since they depend on wetlands for their reproduction, environments threatened with destruction by human development, learning more about salamanders can aid conservation efforts around the Great Lakes.
Greenwald added that seeing the pretty salamanders is also a joy in itself.
“There’s a big part of me that still has that childish appreciation for how cute they are and how delicious it is to roll a log and find those perfect little gummy creatures!” she said. âIf people haven’t spent hours gazing at the spring pools of the woods, observing all the incredible diversity of life that comes in something that looks like a glorified puddle, I couldn’t say enough about it. recommend.”
To learn more about Great Lakes Now:
Great Lakes Moment: Endangered Catfish Indicates Improving Health of Detroit and St. Clair Rivers
Sturgeon restoration: riparian hatcheries on the Manistee, Milwaukee and Maumee rivers
Featured Image: Salamander walking on a treadmill (Photo courtesy of Rob Denton)