Bowfin fish (Amia calva) is an evolutionary enigma representing a unique combination of ancient and modern fish. Charles Darwin even described it as a "living fossil," that has evolved slower than most fishes.
The bowfin fish has many names, like freshwater dogfish, grinnel, and mud pike. Scientists have become interested in them because this species is an evolutionary enigma having ancient and modern fish characteristics.
Researchers from Michigan State University wrote in their study titled "Direct Characterization of cis-Regulatory Elements and Functional Dissection of Complex Genetic Associations Using HCR-FlowFISH," published in Nature Genetics, that they have sequenced the genome of bowfin fish, yielding unexpected insights into the diverse aspects of this ancient lineage.
Genome Sequencing on Bowfin Fish
According to Phys.org, bowfin fish is endemic to eastern North America. It is the only living ancient species that caught the interest of scientists for its unique characteristics. Bowfin fish has the features of an ancient fish with its lung-like air breathing, robust fin skeleton, and simplified scales and reduced fins and tail.
Moreover, bowfin fish occupies a special position in the fish family tree, wherein they are placed between teleosts and more ancient branches of fishes, such as sturgeons, paddlefish, and bichirs.
Genome sequencing on bowfin fish will give scientists information to better understand the origins of teleosts that evolved faster than bowfin fish and emerged as a dominant lineage in most fishes.
The team focused on the fin of bowfin fish because it is a part of them that retains the metapterygium, which are limb bones that are homologous to tetrapods, Earth.com reported.
The genome sequencing results found that bowfin pectoral fins do not have some of the most important appendage growth genes, like the fibroblast growth factor 8 gene (Fgf8).
Study co-author M. Brent Hawkins described this discovery as something like a car running without a gas pedal. Finding this unique characteristic could mean unexpected flexibility in the development of the fins of bowfin fish.
On the other hand, the team also noticed that other genes were unexpectedly activated, like HoxD14, which is expressed in more ancient fish like paddlefish. However, this gene can no longer make a protein which makes scientists think that there might be another function for the gene yet to be discovered.
Bowfin Fish Better Human Health Model Than Teleost Fishes
Bowfin fish may have the characteristics of both ancient and modern fish, but this does not mean that they have not evolved. According to Science Daily, bowfin fish evolved at a slower rate compared to teleost fishes, like zebrafish.
These modern fish are notable examples of fish used by scientists in different scientific models, especially when testing theories about human health. A lot of experiments and research on human biology were done on zebrafish, but identifying important genes that are present in both humans and zebrafish can be hard.
Researchers noted that it is easier to find similarities in genomes between bowfin fish and humans than teleost fishes, like zebrafish. Scientists believe that the last common ancestor of humans and bowfin fish had air-filled organs that were evolutionary predators of human lungs. They found this interesting gene in the bowfin's gas bladder, an organ they use to breathe and store air.
Another air-breathing "living fossil" is the gar. Researchers showed that genetic elements in both aquatic animals are linked to gas bladder and lung formation that are not present in modern teleost fishes. These findings will help establish a bridge between modern fish and model organisms for human biology.
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