Sturgeon are Some of the Fastest-Evolving Fish on Earth: 'Living Fossils' a Myth

Sturgeon look prehistoric with their ridged backs and long "noses." While the species may look like "living fossils," though, the reality is that they've evolved quite a bit over the years. Now, researchers have revealed that sturgeon may just be one of the fastest-evolving fish on the planet.

The new study didn't set out to specifically look at sturgeon. In fact, the new information about the creature is just part of a wide-ranging study of the rates of species formation and anatomical change in fish. The work actually involved one of the largest evolutionary trees ever created for any group of animals, and the evolutionary relationships between nearly 8,000 different species of fish were charted. This allowed researchers to better understand the relationships between about 30,000 species of ray-finned fish.

While this study tells researchers quite a bit about the overall evolutionary picture, it also tells them quite a lot about the sturgeon. The evolutionary tree showed the scientists how quickly new species formed and how rapidly they evolved new body sizes. More specifically, they found a strong correlation between the rates of species diversification and the body size evolution across more than 30,000 living species of ray-finned fish, which comprise the majority of vertebrate biological diversity.

"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," said Daniel Rabosky, assistant professor in the U-M Department of Ecology and Evolutionary Biology, in a news release.

Most of the fish examined fell into one of two categories. There were fish like gar, which form very slowly and show little range in body size. And then there were fish like salmon that form species quickly and vary greatly in body size. Yet there was a third, smaller category which included the sturgeon. The researchers found that these fish, which have been around for more than 100 million years, only consist of a few species but vary greatly in body size.

"Our study shows that sturgeon are evolving very quickly in some ways," said Rabosky. "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."

In fact, the findings seem to hint that in terms of body size, sturgeon evolve extremely rapidly. The new study could show that sturgeon are not "living fossils." Instead, these fish are highly adapted to their environments and evolve rapidly in order to fit their surroundings.

The findings are published in the journal Nature Communications.