A team of scientists from MSU and their foreign colleagues discovered a previously unknown species and genus of batrachians Siamophryne troglodytes. These frogs live in the only one place on Earth -- a limestone cave in Thailand. The location of the cave is not disclosed to protect the animals. The results of the study will lead to the reconsideration of evolutionary history of the relevant group of Amphibia and are valuable for systematics and conservation. The work was undertaken within the Animals branch of the Noah's Ark project (with the support of the Russian Science Foundation), and its results have been published in the Open access PeerJ journal.
The studies of recent 20 years revolutionized the understanding of how diverse the world of frogs, snakes, and lizards is, and in particular how rich is the herpetofauna in South and Southeast Asia. Many species of these animals are difficult to find and some of them are often almost impossible to differentiate from each other. The recent progress in molecular and genetic methods in taxonomy allows the scientists to discover new species every year -- this has become a sort of routine. However, the discovery of a new genus is a fortunate event -- especially when it happens unexpectedly.
The wonderful story of discovery of Siamophryne troglodytes began in 2016 when a Thai researcher Jitthep Tunprasert was working in a karstic region of Sai Yok District in western Thailand. In one of the caves he found a strange small frog with big eyes and finger tips enlarged to wide disks. He took a picture of the animal and shared it with his colleagues. It became clear that this species of Amphibia was absolutely new and unknown to the scientific world. Judging by many morphological characters, the frog was included into a large and diverse family of Microhylidae. However, it was unclear what group within the family it fell into.
"Thai colleagues contacted me because I'm interested in this family of Amphibia. Together, we conducted extensive work, collected specimens, analyzed the DNA and morphology of both adult animals and tadpoles," explains Nikolay Poyarkov, assistant professor and senior research associate of the laboratory for the ecology of terrestrial vertebrates, department of zoology of vertebrates, Faculty of Biology, MSU.
An international team of scientists including herpetologists from MSU took several trips to the cave. Phylogenetic analysis showed that the frogs belong to the subfamily Asterophryinae, the representatives of which live mainly on Northern Australia and Papua New Guinea. These results allowed the scientists to reconsider the story of origin of this group. The fact that the close relatives of Australian and Papua New Guinean frogs were found deep on the Asian continent confirms that their ancestors moved to Asia from the ancient continent of Gondwana and then subsequently moved further east to New Guinea and Australia. Therefore, they did not come to Australia via Antarctica, as it was previously believed. Several other species of amphibians and reptiles took the same way.
Based on the results of phylogenetic analysis, the scientists described a new species and genus of frogs. The specific name "troglodytes" is of Greek origin and is translated as "cave-dweller". The genus name "Siamophryne" can be translated as "Siamese toad" reflecting biological, taxonomic, and geographical peculiarities of this animal. Skeleton structures of the species were studied using the method of X-ray computer microtomography.
Another interesting discovery was the tadpoles of the new species. All members of the subfamily Asterophryinae known to date develop directly from the egg without the larval stage (so called "direct development"). Young Siamophryne troglodytes have flat white guitar-shaped bodies and were found in limestone crevices filled with water. This fact confirms that the frogs did not get into the caves by chance, but live and procreate there permanently.
"The importance of our discovery is manifold. First of all, we've found an animal so different from all others that it is considered to be a separate genius. Things like that do not happen every day. Secondly, phylogenetic position of the new genus sheds light on the evolutionary history of a respective subfamily of microhylids. Finally, this discovery is important in scope of protection and conservation of Southeast Asian herpetofauna. Today we know about only one population of these frogs, and all our search attempts, however intensive, were not successful. Therefore, to protect the animals, we do not disclose the location of the cave," concludes Nikolay Poyarkov.