- New research has found that the scorpion species Charmus indicus from Tamil Nadu is the same as Charmus laneus from Sri Lanka.
- The study also described Charmus dakshini, a new scorpion species from Sirumalai in Tamil Nadu.
- The findings could aid scorpion conservation and biogeographic and medical research.
In 1915, when India was under British colonial rule, English arachnologist Stanley Hirst described a new scorpion species from Coimbatore — Charmus indicus. It was based on a single immature specimen he had found. The yellowing pages of a report by the British Museum in 1916 also include a notable mention of this species under the section Arachnida, which was presented to the museum, alongside parasitic mites from Calcutta and Colombo.
For over a century, scientists assumed C. indicus is widespread across peninsular India, said Shauri Sulakhe, a naturalist who heads the Scorpion Systematics Laboratory (SSL) at InSearch Environmental Society in Pune. But through fieldwork and DNA analysis, Indian researchers have now revealed that C. indicus was a case of mistaken identity — it is actually the same species as Charmus laneus, first described from Sri Lanka in 1879 by German arachnologist Ferdinand Karsch. The researchers were able to establish this based on the lack of physical differences in the appearances and low genetic divergence between the two species.
This finding is part of a research paper published in the journal Diversity in May 2025. The researchers include Shauri Sulakhe, Deshabushan Bastawade, a senior retired scientist from Zoological Survey of India (ZSI), Shubhankar Deshpande and eight others. The research was a result of collaboration between SSL, the Natural History Museum of Geneva in Switzerland and Charles University in the Czech Republic.
Both India and Sri Lanka are major biodiversity hotspots but many of their endemic species are poorly studied. The scorpions from the Charmus genus are endemic to both the countries. Not only are they difficult to identify, they are rarely encountered in the field, with very few specimens available in museum collections. But why is it important to differentiate one species of scorpions from another? “Until you don’t understand species diversity, it’s very difficult to talk about protection and conservation. You need to understand the complexities and abundance of the species, the type of habitats they occupy and whether those habitats need protection,” explained Sulakhe.
In the same paper, the researchers also described a new species, Charmus dakshini, from Sirumalai in Tamil Nadu. They also found a replacement for a neotype (a specimen that acts as a reference) for another species, C. sinhagadensis, another scorpion species, whose holotype (original specimen) had been lost from ZSI collections.
This is also the first time ultraconserved elements (UCEs) data has been used for understanding species relationships of scorpions from India. UCEs are small sections of DNA, shared among evolutionary distant organisms (for example, birds and humans) that have stayed the same during millions of years of evolution.
Searching for scorpions in the dark
The study involved fieldwork spanning four to five years across Tamil Nadu, Kerala, Karnataka and Maharashtra. Charmus is a very elusive species, Sulakhe told Mongabay-India. “Finding Charmus in the field is a challenge. There are a lot of parameters related to environmental conditions such as rain and temperature, which impact its activity.” In Coimbatore, the breakthrough came on the fourth night of fieldwork after nearly giving up. The team had been searching the foothills of Anaikatti, the western mountainous side of the city but found specimens only after searching the grasslands on its eastern side. The collection was done from late evening until early morning because of the largely nocturnal nature of scorpions but it also involved dangers such as the risk of running into elephants in the forests.
The team scoured the ground for scorpions using ultraviolet torches and picked them up with forceps. The scorpions were then euthanised and their specimens preserved in ethanol. The team collected six to 10 specimens of other Charmus species where possible and could find only two to three specimens for C. indicus. Next, during the morphological analysis, they took several different measurements of the specimens. This was followed by molecular analysis in which the researchers extracted DNA from the tissues, which further underwent two types of sequencing — traditional Sanger sequencing and Next-Generation sequencing.
The team had to navigate India’s strict biodiversity norms and a permit process that took almost a year to transport samples to Geneva for further analysis, which required a formal agreement between the Indian and Swiss governments.
And then came the aha moment when the sequences from C. indicus collected in Coimbatore came back. They matched Sri Lankan C. laneus. “I jumped in my chair because I thought that there was a sequencing error,” Sulakhe recounted. To be entirely sure if it was really C. laneus, he checked the data all over again and put a couple more tissues for amplification.
Zeeshan A. Mirza, a biologist who has described several arachnid and reptile species across India, supported the conclusions of the study. “Scorpions are very similar in overall appearance, making it difficult to identify a species in the field, and even a close inspection can often deceive the researcher. The researchers did not leave any stone unturned,” he said in an email interview. He added that most studies on invertebrates, especially arachnids in India, are largely based on morphology, which is concerning and that this study adopts a balanced approach.
Aiding conservation, biogeography and venomics research
The study has wide ranging implications, right from understanding the biogeographical connection between India and Sri Lanka and evolutionary adaptations to aiding conservation and medical research. The Western Ghats in India and Sri Lanka are considered, for research purposes, as one biogeographic region, where mixing and movement of species occurred during periods of lowered sea levels over the last few million years, Sulakhe told Mongabay-India. Finding C. laneus in both locations supports the theory of species movement between these landmasses and the study provides a foundation for testing such a hypothesis in the future, he added.
The study also aids taxonomic clarity for identifying scorpion species in India, which is important for conservation work. The International Union for Conservation of Nature (IUCN) is yet to conduct a global assessment of the status of scorpions because their taxonomic studies are incomplete, explained Sulakhe, who is also a member of IUCN’s Species Survival Commission Spider and Scorpion Specialist Group in South Asia. “Once you have an entire taxonomic index in your hand, then you can start looking at each species, population, number, habitat, habitat type, and habitat conservation requirements.” The team has also deposited the molecular data of Charmus species in the GenBank, a genetic sequence database run by the U.S. government and given the specimens to Bombay Natural History Society so that future researchers can access them.
Scorpions are venomous animals and often feared by people but they play an important role in medical research. There is ongoing research on the use of scorpion venom to treat cancer and autoimmune diseases. Accurate species identification is essential for labelling venom and developing medicines, said Sulkahe.
The study can also be used as a benchmark for setting research standards for studying species in India. “Most studies from India lack molecular data and this paper presents data that aligns with the global standard, helping to fill a significant gap in worldwide scorpion phylogenies,” said Mirza. Phylogeny is the history of the evolution of a species or group. “These phylogenies will help trace the evolutionary history of scorpions of India and Asia.”
Bridging gaps and future research
The study also has gaps, according to Sulkahe. Firstly, not all Charmus species have been included in the ultraconserved elements or UCE dataset as some specimens were collected after the samples were sent for sequencing. The team was not able to collect fresh samples of C. laneus from Sri Lanka due to biodiversity norms and relied on GenBank for data on this species. Additionally, the different populations of C. Sinhagadensis species from Northern Western Ghats need further study to conclude whether they are all the same. Mirza said that he would have preferred to see a dated phylogeny in the study — a time tree that would show when Charmus split from its closest relative and when each Charmus species split from each other, which would allow one to study past geological and climatic events that caused the split. However, it would not significantly alter the results, he added.
To continue this line of work, the researchers plan to do the whole genomic sequencing of Charmus in the near future. They may use this to test a biogeographic hypothesis by dating speciation events and correlating them with geological activity. The team is also planning to conduct UCE-based studies covering various scorpion families and genera, said Sulakhe. Mirza hopes to see similar studies on other scorpion groups of India but noted that UCE sequencing is expensive and not easily accessible. “It may be possible that whole genome sequencing costs drop further, allowing us to use whole genome data to infer species and their distributions,” he said. Sulakhe feels this study has paved the way for future scorpiologists to discover new species easily in India because they can now access the data his team has contributed to the GenBank.
When it comes to scorpions, looks can be deceiving. For now, this new study has managed to solve a 110-year old mystery of a scorpion doppelgänger.
Read more: Scorpion species from Western Ghats highlight need for more research and conservation
Banner image: A specimen of Charmus laneus from Coimbatore, which is the type locality of Charmus indicus. C. indicus has now been synonymised with C. laneus. Image by Shauri Sulakhe.
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