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| Neolissochilus pnar Dahanukar, Sundar, Rangad, Proudlove & Raghavan, 2023 |
Abstract
The world’s largest subterranean fish was discovered in 2019, and was tentatively identified as a troglomorphic form of the golden mahseer, Tor putitora. Detailed analyses of its morphometric and meristic data, and results from molecular analyses now reveal that it is a new species of the genus Neolissochilus, the sister taxon of Tor. We formally describe the new species as Neolissochilus pnar, honouring the tribal communities of East Jaintia hills in Meghalaya, Northeast India, from where it was discovered. Neolissochilus pnar possesses a number of characters unique among species of Neolissochilus, with the exception of the similarly subterranean N. subterraneus from Thailand. The unique characters that diagnose N. pnar from all epigean congeners comprise highly reduced eye size to complete absence of externally visible eyes, complete lack of pigmentation, long maxillary barbels, long pectoral-fin rays, and scalation pattern. Neolissochilus pnar is distinguished from the hypogean N. subterraneus, the type locality of which is a limestone cave ~2000 kms away in Central Thailand, by a lesser pre-pelvic length (47.8–49.4 vs. 50.5–55.3 %SL), a shorter caudal peduncle (16.1–16.8 vs. 17.8–23.7 %SL), and shorter dorsal fin (17.4–20.8 vs. 21.5–26.3 %SL). In addition, Neolissochilus pnar is also genetically and morphologically distinct from its close congeners with a raw genetic divergence of 1.1–2.7% in the COI gene with putative topotype of N. hexastichus and 2.1–2.6% with putative topotype of N. hexagonolepis.
Keywords: Eastern Himalaya, limestone cave, mahseer, new species, subterranean fishes
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| Live images of Neolissochilus pnar in their habitat from Krem Um Ladaw (Photos A, B, C: Uros Aksamovic, D: Dan Harries). |
Neolissochilus pnar sp. nov.
Diagnosis: Neolissochilus pnar is distinguished from all its congeners by mandibular barbel long, reaching anterior margin of opercle (vs. short, not reaching margin of opercle). It is further distinguished from all epigean congeners by atrophied eyes, highly reduced in size in juveniles and small-adults and absence of externally visible eyes in adults (vs. presence of well-developed eyes in all life-stages); complete absence of pigmentation (vs. presence); long pectoral-fin reaching anterior base of pelvic fin (vs. short, not reaching anterior base of pelvic fin); and distinct scalation pattern with 28+2 (2) or 31+1 (1) lateral line scales, 8 scales in transverse series with 4 above the lateral line and 3 below the lateral line. Neolissochilus pnar is distinguished from the only other subterranean congener, N. subterraneus by shorter pre-pelvic length (47.8–49.4 vs. 50.5–55.3 %SL), shorter caudal-peduncle length (16.1–16.8 vs. 17.8–23.7 %SL) and shorter dorsal-fin length (17.4–20.8 vs. 21.5–26.3 %SL).
Etymology: The species name pnar, honours the ‘pnar’, the sub-tribal group of the Khasi people in the state of Meghalaya, India.
Neelesh Dahanukar, Remya L. Sundar, Duwaki Rangad, Graham Proudlove and Rajeev Raghavan. 2023. The World’s Largest Cave Fish from Meghalaya, Northeast India, is A New Species, Neolissochilus pnar (Cyprinidae, Torinae). Vertebrate Zoology. 73: 141-152. DOI: 10.3897/vz.73.e101011
