Hiding in plain sight: New fish species found in Kerala after years of mistaken identity
Researchers said the fish is among several native species threatened by at least four invasive alien species in the Periyar Tiger Reserve.
The discovery of the fish was also unique in the context of the adjacent river systems within the forest, the Periyar and Pamba. (Express Photo/Special Arrangement) A fish that scientists believed they already knew has turned out to be an entirely new species.
Researchers have identified a new species of barb fish in the waterways of Kerala’s Periyar Tiger Reserve, revealing that a population long thought to belong to a known species was in fact distinct. Named Eechathalakenda incognita, the fish had effectively been hiding in plain sight for decades, mistaken for a closely related species found in the neighbouring Pamba river system.
The discovery of the fish was also unique in the context of the adjacent river systems within the forest, the Periyar and Pamba. The previously known species, which is around 20 cm long at most, had already been found in the Pamba, while the new species, E incognita, was discovered in the Periyar River. Until the recent study, it had been thought that the populations in both rivers, which were infrequently studied, were the same species.
Announced in a scientific paper published on June 5 by Swetha Chandra, Rajeev Raghavan, Ravimohanan Abhilash, Ralf Britz, Ryan Babu, and Neelesh Dahanukar, the discovery comes just weeks after researchers described the “crow fish”, Labeo kaage, from Karnataka’s Cauvery basin. It also highlights how much remains unknown about India’s freshwater biodiversity, even within some of the country’s best-studied protected landscapes.
The Indian Express had reported on the discovery of the Labeo kaage in Karnataka.
A DNA test
Scientists found that while E incognita closely resembles Eechathalakenda ophicephalus, detailed examination of its physical features and DNA revealed clear differences between the two. The findings show that the Periyar and Pamba river systems, despite their proximity, harbour distinct fish species that had previously been assumed to be the same.
Speaking to The Indian Express, Raghavan of the Kerala University of Fisheries and Ocean Studies said this had been part of an ongoing effort to document the aquatic life within the Periyar Reserve, which is already known to host nine different “endemic” species not found anywhere else in the world.
“We got this specimen, which superficially resembled Eechathalakenda ophicephalus. When we looked at the specimen in detail, we found that there were several characters which could be used to differentiate it, and found that it is a species new to science,” he added.
Over 18 months of study, the researchers found that E. incognita differed from the known species in several physical traits, including the appearance of its scales. Genetic analysis also revealed a DNA divergence of 4.9-5.3 per cent between the two species — a significant difference, given that humans and gorillas differ by less than 2 per cent.
The endemic nature of this species also exposes it to certain risks. Raghavan said there were at least four alien species competing with and threatening the native fish of the Periyar Reserve, including African catfish, tilapia, common carp and guppies. “Otherwise, the tiger reserve is protected, so these invasive species are the ones posing the threat,” he added.
The study also established that the two species belonged to the subfamily Torinae, which includes carps, barbs, and other species. The most famous members of this group are the huge mahseers, such as the humpback mahseer found in Karnataka, which can weigh nearly 100 kg.
Share
