Sturgeons have often been called "living fossils," but recent research has shown that the prehistoric fish have actually been evolving fairly rapidly, according to the University of Michigan.
Researchers at the University of Michigan found sturgeons are actually one of the fastest-evolving fish that have been studied in regards to their body size.
Charles Darwin came up with the term "living fossil," it's meant to describe a species that's been around for millions of years, but has experienced very little evolutionary change.
"Sturgeon are thought of as a living fossil group that has undergone relatively slow rates of anatomical change over time. But that's simply not true. Our study shows that sturgeon are evolving very quickly in some ways," said Daniel Rabosky, assistant professor in the U-M Department of Ecology and Evolutionary Biology and a curator of herpetology at the Museum of Zoology. "They have evolved a huge range of body sizes. There are dwarf sturgeon the size of a bass and several other species that are nearly as big as a Volkswagen."
The study looked at anatomical changes in fish. It compiled one of the largest evolutionary trees ever created, connecting about 8,000 species of fish.
"The main goal of the project was to test a longstanding idea in evolutionary biology that has anecdotal support but which had never been rigorously evaluated," Rabosky said.
The data set for the evolutionary tree was so large that the researchers had to create an entirely new computer program in order to compile the data.
The program allowed the scientists to study in-depth how the amount of variety within the organism group affects the evolution of body size in fish.
Paleontologists have observed that organism groups that contain a larger variety of species also tend to have a greater anatomical variety. Groups with less species are more likely to be classified as living fossils.
"We're basically validating a lot of ideas that have been out there since Darwin, but which had never been tested at this scale due to lack of data and the limits of existing technologies," Rabosky said.
Most of the fish that were studied either had less species and less development, or many species and a variety of body sizes. Sturgeons were found to be an exception; there are only 29 species of sturgeons, but a vast variety of body sizes.
"In that sense, they're kind of an outlier," Rabosky said.
