India and China may be ‘bhai-bhai,’ but the mud-snakes (‘Cheli kutta’) from Kerala and China are definitely ‘bahin-bahin,’ say a group of scientists who studied the genetic linkages of the Kerala mud snake, an aquatic snake seen across the water bodies in the coastal areas of the state.
Not only have they found the two mud snakes to be similar, but found that their original classification was wrong. The DNA studies have found that the Kerala mud snake, Enhydris dussumierii and the Chinese mud snake Enhydris chinensis are very different from other water snakes in the genus Enhydris that they have come up with new scientific names for both the mud snakes.
So, now the Kerala mud snake is now known in the name, Dieurostus dussumierii, genetically distinct from other mud snake species in India while the Chinese mud snake has been renamed as Myrrophis chinensis.
The study was carried out by a team of scientists including A Biju Kumar of the Kerala University Department of Aquatic Biology and Fisheries; Kate L Sanders, University of Adelaide; Sanil George of the Chemical Biology Group at Rajiv Gandhi Centre for Biotechnology, here and John C Murphy, Field Museum of Natural History, USA.
The results of the study appeared in the current issue of the international journal Systematics and Biodiversity. Not only did the team study the genetics of the mud snake, but they also studied the skull and the salt tolerance pattern, which were similar, suggesting a close relationship between the two.
‘’Though they are related and believed to have originated from the Sunderbans area, we believe that the two would have developed salt-tolerance independently. And among the snakes that now live in freshwater, the salt tolerance gene would have become dysfunctional. This is just a hypothesis, someone would really have to study the salt tolerant genes in these animals,’’ said Bijukumar.
The Indochinese Peninsula and Sunda Shelf contain the greatest species diversity, and the history of these snakes is closely tied to the changing landscape of Southeast Asia. The research paper says that Miocene was a period of greatly fluctuating sea levels.
These dynamic changes in sea-level exerted strong selection pressures on coastal and marine snakes. Coastal snakes that were not salt tolerant or only slightly salt tolerant were forced further inland where fresh water was more readily available. Warming and cooling of the sea surface is also thought to be the major factors that ultimately led to the evolution of many aquatic snakes.
The study is expected to trigger further studies on the genetic linkages of Indian mud snakes and other aquatic snakes. ‘’John C Murphy, who is an expert in this area, suggested that we should study all the water snakes as there is a high probability of mistakes in the identification. In fact, a new research proposal has been mooted by the Department of Aquatic Biology and Department of Computational Biology and Bioinformatics to further the research on this topic,’’ said Bijukumar.