BHUBANESWAR: A century-old confusion on existence of a snake which is sexually dichromatic __ colours of male and female are different __ have been resolved by a group of biologists who have also validated it as a different species for the first time.
The reptile has been renamed as Variable Coloured Vine Snake, the species name being Ahaetulla anomala. This is also for the first time that sexually dichromatism among snakes has been discovered in Indian subcontinent, which is considered a significant feat.
The snake’s presence is limited to Odisha, West Bengal, Jharkhand, Bihar and Bangladesh. For more than 100 years, its separate colour scheme used to get the females clubbed with Brown Vine Snake and the males with Common Vine Snake. The females of the Variable Coloured Vine Snake are brown while the males are an attractive green.
The team of biologists, comprising Pratyush Mohapatra, Prof S K Dutta, Abhijit Das, Niladri Kar, BHCK Murthy and V Deepak conducted molecular and morphological study of the snake to separate it from the Common Vine Snakes. The snake was first spotted near North Orissa University campus in Baripada by Mohapatra and Dutta in 2007, who initiated the study to find out more about the species. “We encountered both green and brown morphs of this subspecies in the repository of ZSI, Kolkata collected from West Bengal, Jharkhand and Bihar, some of which were catalogued as Ahaetulla pulverulenta,” revealed a peer reviewed paper by the six biologists in Zootaxa, an international journal of repute on taxonomy.
The snake was first described by Thomas Nelson Annandale, the first Director General of Zoological Society of India, in 1906. “Apart from several individuals of the species, we also studied the original specimen by Annadale before delving into the molecular and morphology analysis.
We found out that the colour difference between the male and female was the major reason for which this species was confused as a different species,” said Mohapatra, who is a scientist with ZSI at its Central Zone Regional Centre at Jabalpur in Madhya Pradesh.
During the research study that lasted for a decade, the team found that Brown Vine Snake, with which this species was mixed up, is seen in Western Ghats and Sri Lanka while two scientists in 2010 had found the species in Bangladesh. This led to confusion as to how the snake was seen at all these places and the team went into deeper DNA analysis which validated that the Variable Coloured Vine Snake is a valid species and its dichromatic nature came to fore, said Prof Dutta, a pioneer herpetologist and co-author of the paper.
“Sexual dichromatism is rare among snakes and until now documented in some groups such as vipers, Comoran snake and Malagasy leaf-nosed snakes Langaha madagascariensis. Ahaetulla anomala is therefore the first reported sexually dichromatic snake from the Indian subcontinent,” the research paper said.