Unraveling the Mystery of Gars: The Slowly Evolving Living Fossils
The Enigmatic Gar
GARS have been classified as one of the oldest living fossils in a newly published study. The study, published in the journal Evolution and conducted by researchers at Yale, looked at gars for their incredibly slow evolution.
“We show that gars’ slow rate of molecular evolution has stymied their rate of speciation,” said Thomas J. Near, professor of Ecology and Evolutionary Biology in Yale’s Faculty of Arts and Sciences and the paper’s senior author, per Phys.Org.
“Fundamentally, this is the first instance where science is showing that a lineage, through an intrinsic aspect of its biology, fits the criteria of living fossils.”
Decoding Gars: The Ancient Ray-Finned Fish
One of the most ancient groups of ray-finned fish, gars belong to the family Lepisosteidae. The fish have elongated bodies and similarly elongated jaws that contain long, sharp teeth. The largest type of gar – the alligator gar – often grows to a length of over 6.5 feet and can weigh over 100 pounds.
The Phenomenon of Living Fossils
All of the jawed vertebrates, which comprise roughly 60,000 species, gars have the slowest rate of molecular evolution. Basically, this means that their genome has changed very little since their ancestors originated around 150 million years ago.
“Gars are notable for their low anatomical variation,” the study reads. “The earliest fossil gars from the Jurassic are nearly identical to living species, and recognizable members of living genera appear in the fossil record as early as the middle Cretaceous.”
This very little change in their physical form, and when compared to extinct ancestors, are two of three characteristics that make gars a “living fossil,” lead author Chase Brownstein told Live Science.
Unveiling Genetic Mysteries
The third characteristic is that the species has diversified into a small number of related species. For the study, researchers used computer analysis to study gene sequences that came from common ancestors. This is known as orthologs and helped to determine the rates of mutation, or gene substitution over time.
“Once a mutation fixes and changes a particular DNA sequence, it becomes a substitution,” Brownstein said. The researcher added that identifying exactly how the genomes of gars have remained so stable is of big interest. “There’s a mechanism behind the low substitution rate as well,” he said. “There’s some sort of apparatus that we think is probably related to DNA repair.”
The team hopes to analyze their findings further as this research could offer insight into the genetic health of humans – and particularly, cancer-related issues.