Researchers have revealed surprising diversity in the genetic mechanisms that determine the sex of the African clawed frog, marking an important finding regarding one of the most extensively examined amphibians globally.
McMaster researchers have revealed surprising diversity in the genetic mechanisms that govern the sex of the African clawed frog, marking a significant finding regarding one of the most extensively studied amphibians globally.
A genomic study has identified eight distinct sex chromosomes among just 11 species of this frog, many or all of which could harbor unique and newly emerged genes responsible for male or female sexual development.
Previously, only three sex chromosomes were known to exist in these frogs.
“We have observed remarkable variation in these frogs, even among closely related species, enabling us to investigate how crucial elements like sex determination can evolve swiftly,” says Ben Evans, a professor in the Biology department and the lead author of a new study published in the journal Molecular Biology and Evolution. Evans collaborated with colleagues from the Czech Republic, France, the U.S., and South Africa for this research.
The African clawed frog is utilized as a model organism for scientific research due to its close evolutionary kinship with humans, in addition to its external early development, which allows for the easy observation and manipulation of fundamental processes.
These frogs inhabit sub-Saharan Africa and are typically found in slow-moving or stagnant waters. They are characterized by their flat physique, vocal structures capable of producing sounds underwater, and claws on the first three toes of their hind feet, which they use for tearing their food apart.
In this research study, scientists outlined the locations of the newly discovered sex chromosomes, further adding to their astonishment.
Traditional theories suggested that genes responsible for sex determination generally emerge in genomic areas with a low rate of recombination — the process that mixes genetic material from parents, creating new combinations of traits in offspring.
However, in this study, the researchers found that these newly evolved genes were predominantly located in regions characterized by high genetic recombination, prompting inquiries into how and why the genetic foundations of significant biological traits — like sexual differentiation — might evolve so rapidly, as well as how new genes and genetic functions are developed.
“If similar studies were conducted on older species like most mammals or all birds, you would see that their sex chromosomes remain consistent,” explains Evans. “In stark contrast, this group of frogs showcases incredible diversity.”
“It’s very likely that new genes have emerged multiple times in these frogs to manage sexual differentiation, acting as a type of ‘on-off switch’ or a ‘male-female switch’ at the beginning of developmental processes,” he adds.
In 2015, Evans — who has been studying the African clawed frog for over 20 years — led a team that discovered six new species and reintroduced another to the known species list, laying the groundwork for further research, including the latest study.
