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| Schistura sonarengaensis Mukhim, Sarma, Choudhury, Chandran, Das, Singh, Warbah, Sarkar & Sarma, 2024. |
Abstract
A new species of nemacheilid loach, Schistura sonarengaensis sp. nov., is described from three cave-dwelling populations (Barak–Surma–Meghna drainage) in the South Garo Hills district of Meghalaya, India. The new species possesses prominent eyes but is easily distinguished from all the congeners of the genus Schistura from Barak–Surma–Meghna and adjacent rivers drainages of northeast Indian (except S. syngkai) in having 13–26 vertically elongated to circular mid-lateral black blotches (brownish in life) overlayered on a grayish-black mid-lateral stripe on a dull white or pale-beige (golden brown in life) body. However, it can be easily distinguished from S. syngkai in having a complete (vs. incomplete) lateral line with more 72–89 (vs. 19–42) lateral-line pored scales, greater pre-dorsal length (48.5–53.1 vs. 41.9–44.1 %SL), a wider body at dorsal-fin origin (11.3–16.7 vs. 9.4–10.3 %SL), greater dorsal (18.1–21.1 vs. 15.1–17.0 %SL) and lateral (20.9–24.1 vs. 17.4–18.9 %SL) head length, a wider head (14.5–18.5 vs. 11.6–13.3 %SL), and moderately forked (vs. emarginated) caudal fin. Further, molecular analysis confirms the distinctiveness of S. sonarengaensis sp. nov. from its congeners found in northeast India by significant divergences with uncorrected genetic distance ranging from 3.7% to 17.3% in the mitochondrial cytochrome c oxidase subunit I (COI) gene dataset. The phylogenetic position of the new species with its sister species was evaluated using maximum likelihood and Bayesian analysis. The species delimitation approaches assemble species by automatic partitioning (ASAP) and Poisson tree processes (PTP) utilized for testing species assignments consistently identified our test group as a distinct species from its sister species. Although the new species lacks typical morphological adaptations usually associated with a subterranean life, such as complete absence (or vestigial presence) of eyes and pigmentation, it exhibits a reduction of pigmentation when compared to the epigean congeners.
Keywords: Barak–Surma–Meghna drainage, biodiversity hotspot, limestone cave, Meghalaya, new loach, subterranean life, taxonomy
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| Holotype of Schistura sonarengaensis sp. nov. (GUMF 1001, 72.8 mm SL), India: Meghalaya: Krem Sonarenga; dorsal (a), lateral (b), and ventral (c) views. |
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| Live coloration of Schistura sonarengaensis sp. nov. GUMF uncatalogued, , about 63 mm SL; India: Meghlaya: Krem Chiabole. |
Schistura sonarengaensis sp. nov.
Dran Khlur B. Mukhim, Kangkan Sarma, Hrishikesh Choudhury, Rejani Chandran, Rajdeep Das, Rajeev K. Singh, Deisakee P. Warbah, Uttam Kumar Sarkar and Dandadhar Sarma. 2024. Schistura sonarengaensis, A New Species of Cave-dwelling Loach (Teleostei: Nemacheilidae) from Meghalaya, northeast India. Journal of Fish Biology. DOI: doi.org/10.1111/jfb.15856
