A new genus of freshwater fish from the estern Ghats — ‘Koima’ — has been described by researchers in India. The two species of fish earlier identified under genus Nemacheilus have been reclassified under the newly coined genus.
The finding is especially significant as new species are continuously discovered across the globe but the addition of a new genus in the nomenclature is comparably a rare event.
The fish named Mesonoemacheilus remadevii and Nemacheilus monilis are now renamed as Koima remadevii and Koima monilis — a small, elongated bottom-dwelling freshwater fish used for dietary and ornamental purposes.
Both species are endemic to the Western Ghats and found in the tributaries of the Cauvery river.
Neelesh Dahanukar, assistant professor at Shiv Nadar Institution of Eminence, Delhi and co-author of the study titled Koima, a new genus of nemacheilid loach from the Western Ghats, India (Cypriniformes: Nemacheilidae) told Down To Earth (DTE) that the need to re-examine the study of the fish was attributed to its broad classification under the Nemacheilus genus.
“The species of genus Nemacheilus are found in South East Asia and their geographic distribution was considered to be large. But Anoop, a Phd student at Kerala University of Fisheries and Ocean Studies (KUFOS), Kochi working on hillstream fishes of the Western Ghats, explored the species Nemacheilus monilis further as it was unlikely the genus was so vastly distributed in India and Southeast Asia,” he said.
Dahanukar said the hypotheses led to initiating an integrative approach to re-evaluate the taxonomic status.
Upon close observation, it was found that the morphological characteristics were also different from their counterparts. Further phylogenetic analysis revealed the species to be entirely different. Hence, the scientists named a new genus of nemacheilid loach as Koima, meaning ‘loach fish’ in Malayalam and used as a vernacular name for loaches in the language.
“It is distinguished from all other genera of family Nemacheilidae by its unique colour pattern comprising a yellowish-brown ground colour, single row of black spots on lateral line, all fins hyaline, and absence of a uniform banding pattern on dorsal side,” an article published in Zootaxa observed.
In addition, it can be identified by other morphological characteristics.
The scientists picked specimens from the Kunthi (Bharathapuzha Basin), Bhavani, Moyar, Kabini and Pambar rivers in the Cauvery basin of the Western Ghats range.
Dahanukar said the research highlights that the biodiversity of the Western Ghats is unique and remains largely unexplored, especially with regards to loaches.
“There is potential to discover more species from the region and crucial to protect and conserve the Western Ghats. The unique and micro habitat of the loaches in narrow regions of Kerala underline how vulnerable they are to anthropogenic disturbances and impacts of climate change,” he told DTE.
Specifying the narrow range of habitat, the finding observes that Koima remadevii is mainly found in swift-flowing riparian streams with substrates comprising rocks, boulders, and gravel, with sand and silt patches scattered throughout. These surface materials serve as a range of microhabitats, such as gaps under boulders, and clefts between rocks that provide protection from powerful currents.
“Koima monilis typically inhabits swift-flowing streams with substrates mostly comprising rocks, boulders, gravel, and sand. The species occurs in localities spread across an altitude range between 350 m to 800 m, in microhabitats ranging from large tributaries to several smaller, swift-flowing streams,” the researchers noted.