The latest among the species named after Arunachal Pradesh’s pristine forests is an invertebrate found scuttling on the edge of a small stream in Namdapha Tiger Reserve. The name of Abortelphusa Namdaphaensis, a small freshwater crab species, is a tribute not just to Namdapha, the largest protected area in the Eastern Himalayan Biodiversity Hotspot, but also to the Abor Hills, another rich biodiversity hotspot in Arunachal Pradesh.
“This is our way of honouring both,” said Santanu Mitra, an assistant zoologist at the Crustacea division of the Zoological Survey of India (ZSI), who has consistently explored the area since 2011. “There is so much ground to be covered in these areas, so much work to do – as researchers, it is our duty to honour these places and increase awareness about them,” said Kolkata-based Mitra.
Namdapha (named a National Park in 1983) is known for its rich biodiversity, and believed to be the rare area that harbours four large cats: tigers, snow leopards, clouded leopards and leopards.
The Abor Hills, bordered by the Mishmi Hills and Miri Hills, are historically known for the Abor Expedition — a punitive expedition against the Abors in the North-Eastern Frontier Agency (which corresponds to parts of present-day Assam and Arunachal Pradesh) from October 1911 to April 1912. The expedition had thrown up a plethora of new floral and faunal species, making it a zoological and botanical expedition as well.
“In 2019, we (a group of ZSI researchers) had retraced the expedition route and even then rediscovered a number of species,” said Mitra.
However, the Abortelphusa Namdaphaensis was spotted before that — in 2017, when a ZSI team had visited Namdapha under the program “Long-term monitoring of Himalayan Diversity.” “I had not travelled then but those researchers who did had collected a number of specimens, and subsequently distributed them to experts in Kolkata — this crab was founded by J Saini,” said Mitra.
The discovery was published in the Crustaceana journal — a leading peer-reviewed journal on crustacean research — in September, 2020. While the genus (Abortelphusa) is named after the Abor Hills, the species (Namdaphaensis) is named after Namdapha.
“What amazes me about this species is that it is the first Gecarcinucidae to be found in the Himalayan region,” said Mitra, explaining how freshwater crabs are divided into two families/categories: Potamidae and Gecarcinucidae. Both differ in abdomen shape and size. “Potamidae species have a broad triangular abdomen, whereas in Gecarcinucidae, the abdomen is mostly T-shaped,” said Mitra.
“While the Gecarcinucidae is found in the peninsular region, Western Ghats and Eastern Ghats, Potamidae are found in the Himalayan region,” he said, “So it was very unusual to find them here.”
In 2018, Mitra had discovered the Teretamon ke-mpi, a freshwater crab belonging to the Potamidae family, residing in creeks and semi-dry areas.
The new species, too, was found in a dry area, despite being a “freshwater” crab. “Fresh water crabs use their gills to absorb dissolved oxygen from water, but for food, breeding, and other purposes, they do not need water, and thus roam on the land near water,” Mitra explained, “The only reason it was possible to spot this on land is because the habitat around the water body has been preserved, untouched even. Imagine if it was concrete or built, then we would have never found this. So it is all the more important to preserve such areas.”
The discovery highlights the potential of Arunachal Pradesh as one of the richest biodiversity hotspots in the country. “Of the 125 freshwater crabs in India, the north-east accounts for 37. Arunachal Pradesh has 15 and Assam has 21,” said Mitra.
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