A new species of  glyptosternine catfish,  Exostoma sentiyonoae, has been identified from the Dzuleke River, a tributary of the Barak River in Nagaland. The discovery was detailed in the scientific journal Zootaxa (Vol. 5447), in an article authored by Bungdon Shangningam from the Zoological Survey of India, Kolkata, and Professor and Dean of Sciences, Kohima Science College,  Limatemjen.

Exostoma sentiyonoae, holotype ZSI FF 9871, 75.8mm SL. Dorsal, lateral, and ventral views (Image Credit: Shangningam, B. & Limatemjen (2024). “Exostoma sentiyonoae, a new catfish (Teleostei: Sisoridae) from Nagaland, Northeastern India,” Zootaxa, 5447 (3), pp. 424-432.)

This marks the fourth species of Exostoma described from the Barak drainage, highlighting the region’s rich biodiversity. According to the research paper, the species can be distinguished by several unique characteristics, including an adipose fin attached to the upper procurrent caudal-fin rays, tubercles on the dorsal-fin spine, a slender head, a long distance between the dorsal and adipose fins, small eyes, and 41 vertebrae.

In their research, the authors proposed two distinct species groups within the genus Exostoma based on the attachment of the adipose fin to the caudal-fin rays.

The researchers distinguished Exostoma sentiyonoae from its congeners in the Salween drainage of Myanmar and Thailand, specifically E. berdmorei and E. gaoligongense.

Notably, E. sentiyonoae differs from E. berdmorei in having a shorter dorsal-fin base, a longer dorsal-adipose distance, and a smaller eye. Compared to E. gaoligongense, the new species has a shorter pectoral-pelvic distance and a smaller eye.

Additionally, E. sentiyonoae can be differentiated from two species found in the Chao Phraya drainage in Thailand. For instance, it is distinct from E. effreni due to its adipose fin being confluent with the upper procurrent caudal-fin rays (versus separate in E. effreni), a wider head, and deeper caudal peduncle. It also differs from E. peregrinator in having a longer dorsal-adipose distance and a shorter anal-fin base.

Exostoma sentiyonode is the first known member of this genus discovered from the Dzuleke River in Nagaland. According to the authors, the hilly terrain and inaccessibility of the region have resulted in relatively few ichthyological explorations. However, the region’s unique landscape, physiography, and diverse aquatic habitats make it a promising hotspot for future ichthyological discoveries, particularly for hillstream fish species. Comprehensive inventories and scientific surveys including those that use genetic tools will provide valuable insights into the fish fauna of Nagaland.

Additionally, studying the distribution patterns, ecological interactions, and conservation status of these newly discovered fish species will help inform long-term conservation and management. Focusing research efforts on the remote streams and less-explored regions of Nagaland can help contribute significantly to our understanding of the fish diversity in the state, and in the larger Eastern Himalaya and Indo-Burma Biodiversity Hotspots.

The authors acknowledged support from the Zoological Survey of India and the Zoology department of Kohima Science College. This study emphasizes the need for more focused research on Nagaland’s remote streams to better understand the region’s rich fish diversity.

MT

One thought on “New species of catfish discovered in Dzuleke River, Nagaland”
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