Study unveils new fish species in Western Ghats, solves evolutionary riddle

A team of scientists has discovered a new fish species and successfully resolved a decades-old evolutionary mystery surrounding one of the most elusive aquatic lineages in the Western Ghats.

Published in the journal Systematics and Biodiversity, the study details the unexpected discovery of Eechathalakenda incognita, a new species of cyprinid fish (Torinae), described from various streams inside the Periyar Tiger Reserve. This newly described species had been confused with Eechathalakenda ophicephala for the last 70 years. Both species have restricted distribution and face habitat threats, suggesting a high risk of extinction and that they are an urgent priority for conservation efforts.

Eechathalakenda incognita is the ninth point-endemic fish species (restricted to a single location in the world) to be identified within the Periyar Tiger Reserve. This discovery also marks the reserve as one of the most critical sanctuaries for freshwater fish conservation, not just in India, but across the entire Asian continent.

The genus Eechathalakenda was originally established in 1999 for a solitary, enigmatic fish species first described in 1941 from the Pamba River in Kerala. For over eighty years, the fish remained largely invisible to science, with its existence noted only in brief regional checklists that lacked proper taxonomic verification, photographs, or preserved specimens.

Driven by a quest to locate this elusive creature, a team of researchers—Swetha Chandra, Rajeev Raghavan, Ravimohanan Abhilash, Ralf Britz, Ryan Babu and Neelesh Dahanukar—from St. Stephens College, Pathanapuram; Christian College, Chengannur; KUFOS, Kochi; and Shiv Nadar Institution of Eminence, Delhi NCR conducted extensive fieldwork in the remote, high-altitude headwaters of the Pamba and Periyar rivers. Upon analysing the physical characteristics and DNA of the newly collected specimens, they realised they were looking at two completely distinct species that had been confused as one for the last 70 years.

Distinctive characteristics

Using advanced mitochondrial DNA sequencing, the team mapped the complete mitogenome of the hidden species, officially naming it Eechathalakenda incognita in reference to its long-running scientific anonymity. The newly identified Periyar Channa Barb is visually and genetically distinct from its sister species, E. ophicephala. While E. ophicephala sports rhomboid-shaped scales, the new species features circular scales near its upper body, alongside a unique dark lateral stripe, a different count of fin rays, and a substantial 4.9%-5.3% genetic variation. Crucially, the genetic data also allowed researchers to firmly place the entire genus within the cyprinid subfamily Torinae, finally providing a definitive evolutionary home for this ancient lineage.

Despite the excitement of the discovery, scientists are sounding an urgent alarm regarding the survival of both species. Their geographic distributions are exceptionally narrow; E. ophicephala is strictly confined to Pamba river headwaters over 1,000 metres above sea level, while E. incognita is isolated to specific fast-flowing, rocky streams inside the Periyar Tiger Reserve. Because they are confined to such restricted habitats, localised threats like climate shifts and habitat degradation put both fish at an extreme risk of extinction.