Long ago in a cozy cave stretching through Indiana and Kentucky, a fish population took refuge in the sheltered waters the cave provided from glaciers.
Sometime after that, the fish population separated as the infrastructure of the cave shifted and cut off interaction between the two fish populations.
The differences that developed between the two populations are subtle but led to a new species of cavefish named recently through the work of LSU and University of Kentucky researchers.
The newly discovered species in Indiana, dubbed Amblyopsis hoosieri or the Hoosier cavefish, has no eyes. It has short fins and a relatively chunky appearance compared to the slimmer close relatives found south of the Ohio River in Kentucky caves. Both fish grow up to 4 inches long, considered very large for cave-dwelling fish.
Although neither of the fish have eyes, the newly discovered species still retains the gene rhodopsin, which is important to vision, said Prosanta Chakrabarty, assistant professor and curator of fishes at the LSU Museum of Natural Sciences and one of the researchers who published the findings in the journal ZooKeys.
The southern cousins of the new species lost that vision gene some time in the past.
“The DNA gave us the hint that these fish are distinct species,” Chakrabarty said. “I just thought it was cool that they’ve had a functional one (rhodopsin gene) for all this time.”
The discovery of the Hoosier cavefish came through work being done by Matthew Niemiller, a post-doctorate researcher at the University of Kentucky and affiliated with research at the LSU Museum of Natural Science.
That work started with his dissertation on genetics in cave systems with the overriding question being whether the Ohio River acted as a barrier for fish species to the north and south.
He concluded the river did act as a barrier to fish species. However, the fact that fish on either side of the river have different genes doesn’t automatically mean they are different species.
The researchers also looked at the physical characteristics of the fish, and that’s when they determined the Hoosier fish was something different.
“It’d be nice if the differences were as different as those between tigers and lions,” he said. “But it’s not that easy.”
Although Chakrabarty has gotten to name a new species before, this was Niemiller’s first. Hoosier cavefish honors Indiana University, the birthplace of North American fish research where scientists like Carl and Rosa Eigenmann and David Starr Jordan worked in the late 1800s and early 1900s to describe fish species.
“Indiana was the mecca for North American ichthyology,” Niemiller said.
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