by Ashvita Anand
-Genetic testing shows likelihood of more than one species of the banded krait. -There are at least three different species that were previously categorised as the banded krait; the populations in eastern and north-eastern India are of the same species. -It is necessary to accurately identify and delineate snake species, especially those that are venomous, because of the implications of the composition of snake venom and what this means for developing efficient anti-venom.
A recent study finds that the highly venomous banded krait (Bungarus fasciatus) is likely to be an assemblage of different species across Asia.
In recent years, genetic analysis methods have been increasingly used to identify cryptic species (species that may look identical but are evolutionarily distinct lineages) in vertebrates. These methods have been employed to identify genetically different species in reptiles and snakes.
The banded krait is a nocturnal, easily identifiable snake that inhabits different landscapes like agricultural lands, forests, and home gardens up to specific elevations. It has yellow (or cream) and black bands on its body. The range of this venomous snake is widespread, from eastern India, across Nepal, Bhutan, Myanmar, and Bangladesh, further east into Laos, Vietnam, and China, and south into Thailand, Malaysia, and Singapore.
The IUCN Red List currently classifies this species as a species of least concern. The focus of research on this species has been on its medical importance, properties of its venom, and ecological significance.
While some studies have noted the possibility of differences within species using methods such as genetic barcoding, there has been no systematic study on its taxonomy until now.
Studies, such as this one, are necessary to accurately identify and delineate snake species, especially those that are venomous, because of the implications of the composition of snake venom and what this means for developing efficient anti-venom.
Is one species really three?
The study, carried out by Lal Biakzuala of Mizoram University and a team, sheds light on the genetic diversity and evolutionary relationships within the banded krait species. The team included researchers from Society for Nature Conservation, Research and Community Engagement, West Bengal, Universitas Indonesia and Bangor University.
Using a combination of genetic and physical structure analyses, they identified three distinct evolutionary groups of the banded krait occupying non-overlapping regions – Indo-Myanmar (east and north-east India and Myanmar), Sundaic (Greater Sunda islands), and east Asian (mainland Sundaland including southern China).
Data of the physical structure of the snakes for this study was collected from 15 specimens captured and euthanised in north-eastern India between 2007 and 2022.
Blood samples were also taken from captured individuals in West Bengal and their physical characteristics noted down, after which they were released. The subsequent results were then compared to both unpublished and available data.
An interesting finding from the analyses of one common gene across the three groups revealed that the Indo-Myanmar and Sundaic lineages had negligible genetic differences within themselves whereas the east Asian lineage contained a wider range of genetic differences.
The authors speculate that the east Asian lineage could contain more diversity that is not obvious based on appearance and should be studied further in order to distinguish them.
The physical markings of the specimens showed differences between the Indo-Myanmar and Sundaic populations, further supporting the team’s findings.
According to the authors, “We postulate the existence of at least three different taxonomic entities within the nomen B. fasciatus, and also confirm that populations in eastern India and north-eastern India are conspecific (belonging to the same species).”
In other words, there are at least three different species that were previously categorised as the banded krait, and that the populations in eastern and north-eastern India are of the same species.
The study goes on to state that if these three different groups are accepted as independent species, that the Indo-Myanmar group is the original banded krait species that was first described in 1794; however, more generally, the east Asian and Sundaic groups may be referred to as banded kraits as well.
This definition of the original banded krait species is based on the first descriptions of it, by Patrick Russell in his book An account of Indian serpents, collected on the coast of Coromandel containing descriptions and drawings of each species, together with experiments and remarks on their several poisons.
When asked about future plans for the team, Hmar T. Lalremsanga, at Developmental Biology and Herpetology Laboratory, Department of Zoology, Mizoram University, a member of the research team said, “At present, new species description is under process, out of the three clades, the East Asian lineage and Sundaic clades are supposed to be new species.” Clades are a group of organisms composed of a common ancestor and all its lineal descendants.
What does this mean for the banded krait and anti-venom?
The finding that the banded krait may actually be three distinct species does not seem to have implications for its conservation status. According to Lalremsanga, “I do not think the delineation into three clades would have an effect on the conservation status of this species since they are quite common in their distributional range.”
Kartik Sunagar from the Evolutionary Venomics Lab at the Indian Institute of Science, Bangalore, who was not associated with the study, adds, “Taxonomy is amongst the oldest streams of science that still holds a lot of value today.
Identifying hidden diversity of life is important to design better conservation strategies. If you know that a particular population/species has limited geographic distribution or is restricted in terms of the habitat it is found in, then special efforts are needed to conserve such species.”
This identification of three distinct groups of the banded krait could have implications for anti-venom preparation. On this note, Lalremsanga says, “Previous research by the team has shown variation in venom among closely related species, and among banded. Krait individuals in India. With the help of taxonomy, further investigation and development of antivenom from different regions is needed.”
Sunagar adds, “Regional antivenoms should be manufactured for treating snakebites in India. We are taking this step by working with industry partners and producing India’s first regional antivenom products. These changes represent probably the first major change to our antivenoms in over 100 years.”
Moreover, “Phylogenetics is important for designing a better snakebite therapy, but in this context, it probably has limited implications. This is because the banded krait isn’t a medical threat in places where it is found.
It rarely bites people. Our previous work has shown that because it is a snake specialist (or exclusively/mainly feeds on other snakes), its venom has relatively less potency against mammals while being very toxic to other snakes.
This article first appeared on Mongabay here
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