When you see a horseshoe crab or a coelacanth, it's like taking a journey back in time millions of years. These creatures, along with the duck-billed platypus, are often referred to as "living fossils" because they closely resemble their ancient ancestors found in the fossil record.
Now, researchers have uncovered a new contender for the title of ultimate living fossil: the gar, an ancient group of ray-finned fishes. A recent study published in the journal Evolution reveals that gars have the slowest rate of molecular evolution among all jawed vertebrates, making them remarkable survivors from prehistoric times.
So, what exactly are gars? There are seven known species of gar found in North America, inhabiting various aquatic environments from freshwater to saltwater. These fish have sleek bodies resembling darts and elongated snouts resembling forceps. Interestingly, they lay green-colored eggs that are highly toxic to predators.
What sets gars apart is their remarkable resemblance to their ancient ancestors. All seven living species of gars closely resemble fossils dating back about 150 million years to the Jurassic period. Even after millions of years, gars have retained their distinctive features, showcasing their remarkable evolutionary stability.
In the recent study, researchers analyzed the DNA of gars and found that their genetic makeup evolves at an exceptionally slow rate compared to other vertebrates. This slow rate of evolution has allowed gars to remain genetically similar to their ancient ancestors over millions of years.
Furthermore, the study examined hybridization among different gar species, where two species produce viable offspring capable of reproduction. Remarkably, despite diverging from a common ancestor over 100 million years ago, some gar species can still interbreed and produce fertile offspring. This successful reproduction is attributed to the slow rate of genetic change in gars, which has kept their species count low.
The researchers speculate that gars possess a robust DNA repair mechanism that efficiently corrects genetic mutations. This unique ability may have implications for human health, particularly in understanding and potentially treating diseases related to DNA mutations.
The study sheds light on the remarkable resilience of gars as "living fossils" and provides insights into the mechanisms of evolution. By studying these ancient fish, researchers not only gain a better understanding of Earth's biodiversity but also uncover potential applications for medical research to improve human health.