Canadian scientists discovered six new African clawed frog species under the genus Xenopus, increasing the number of identified species by 30 percent. The discovery provides new opportunities for studies on human diseases.

Frogs are one of the most studied amphibians across the globe. Thus, the discovery of new species will provide more information for studies, particularly on human disease research.

"Because the African clawed frog is used as a model organism for biological research, it would be understandable to think that scientists had already pinned down the number of species and other aspects of their diversity such as where they live and how they are related to one another," lead author Ben Evans, an associate professor for the Department of Biology at McMaster University, said.

"But this isn't the case," he added.

African clawed frog is a unique family of amphibian frogs that do not have a tongue nor any visible ear. The body is flat. The hind legs are large, webbed and the three inside toes have claws, hence its name. Interestingly, the males lack vocal cords.

One of its unique characteristics is that it can change its appearance to match the background. Sometimes, its skin may change to a darker shade, lighter color of even mottled.

These frogs are often found along the African Rift Valley south of the Sahara in east and southern Africa. They live in quiet or stagnant water and contain a lateral line system that is very sensitive to the movement of water.

As a very versatile species, they can withstand wide water pH variations and temperatures from 60 to 80 degrees Fahrenheit.

The researchers analyzed the frogs' evolution through techniques that use DNA, voice recordings, CT scans of their internal anatomy, and chromosome analysis.

Findings show that the newly-identified species are "polyploid". This means that they contain more than two paired sets of chromosomes. This is common among some plants and amphibians.

Polyploids occur when an unusual cell division, either through mitosis or meiosis, happens. Thus, it causes the formation of gametes or sexual reproduction cells that have a complete set of duplicate chromosomes.

The study was published in the journal, PLOS ONE.