Lookalike snakes but with self-styled venoms

Number one: The Sind krait (seen in the picture) has been identified as the snake with the most potent venom in India.   | Photo Credit: Shubham N. Kurundwadkar

A study of snakes in southern and western India has identified a new species of snake. Named the Romulus’ krait (Bungarus romulusi) after the ‘snake man of India’, Romulus Whittaker, the species has so far remained undetected because of its similarity in appearance to the common krait (B. caeruleus) and only a careful genetic analysis revealed that the two were distinct species. The study also showed that some kraits in Maharashtra that were misidentified as the Wall’s Sind krait were actually the same as the Sind krait which is also found in parts of Pakistan and Rajasthan and has been identified as the snake with the most potent venom in India. This study, published in Toxins, was conducted by scientists from the Indian Institute of Science, Bengaluru (IISc), in collaboration with members of the Liana Trust and the Indian Herpetological Society, based in Pune.

Surface likeness

Though the Sind krait and the common krait may look identical to a wayside observer, morphological differences do exist between the two. “The former has 17 dorsal scales at the mid-body, while the latter has 15,” says Kartik Sunagar, who heads the Evolutionary Venomics Lab at IISc and is the lead author of the paper, in an email to The Hindu. “The Romulus’ krait and common krait are so hard to distinguish that even herpetologists with years of experience couldn’t tell that it could be a distinct species through casual observation. Only after the genetic examination, we were surprised to discover a new species,” he adds.

The Wall’s Sind krait was originally described in the Oudh state by a British herpetologist as a distinct subspecies. “Our comparisons between the Wall’s Sind krait in Maharashtra and the Sind krait in Pakistan clearly revealed that there are only minor variations in their genes, suggesting that there is no evidence to support the identity of this subspecies,” explains Dr. Sunagar.

When the researchers compared certain gene sequences of the common krait (Maharashtra), the Romulus’ krait (Karnataka) and the Sind krait (Pakistan), they found that there were significant differences. Similar comparisons between the Wall’s Sind krait population in Maharashtra with the Sind krait population in Pakistan showed only 0.3% to 3% difference.

“This doesn’t mean that the Wall’s Sind Krait doesn’t exist – it may still do in certain regions of North India where it was originally described. Our results show that, at least, the 17 mid-body scale kraits in Pune, Maharashtra that we examined are not distinct from their counterparts in Pakistan,” says Dr. Sunagar.

Venom analysis

The group also found that the venoms of the snakes were very different compositionally from each other and this reflects in their toxicity. The venom of the Sind krait was 12–13 times as potent as that of the common krait, whereas the venom of the Romulus’ krait was about six times as potent. When the Indian antivenoms were tested for their ability to neutralise the venoms of these cryptic kraits, they were found to be ineffective. This is because these antivenoms are made to protect against the bites of the ‘big four’ Indian snakes – the spectacled cobra (Naja naja), common krait (Bungarus caeruleus), Russell’s viper (Daboia russelii) and saw-scaled viper (Echis carinatus). In a situation where about 58,000 people die in India every year due to snake bites and three times this number suffer permanent disabilities, it is necessary to take cognisance of the difference between the venoms of the different species and their distribution across the country, according to the researchers.

Sequencing the venom glands, the group found that while the abundance of RNA that codes for the toxin proteins was similar, each krait species was producing distinct compositions of proteins (toxins) using the same set of RNA. “There are molecular mechanisms that have been described that can contribute to this. However, more work is needed to fully understand this,” he says.

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Printable version | Mar 1, 2021 4:20:20 AM |

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