Tuesday, August 22, 2017

[Ichthyology • 2017] Schistura thavonei • A New Species of Loach (Teleostei: Nemacheilidae) from northwestern Laos


 Schistura thavonei  Kottelat, 2017

RAFFLES BULLETIN OF ZOOLOGY. 65


  Abstract
 Schistura thavonei, new species, is described from the Nam Ma, Mekong drainage, in Louang Namtha Province, northwestern Laos. It is distinguished from all other Nemacheilidae by its unique colour pattern made of two broad dark brown stripes (one middorsal, one midlateral) and between them a pale yellowish-brown stripe (iridescent in life); a row of 12–24 short black bars are located increasingly lower on the flank from head to tail, posterior-most ones restricted to the lower half of the body or forming blotches along the ventral midline of the caudal peduncle. Besides, it has an elongate body with a hump immediately behind the head, 8+7 branched caudalfin rays; and 9–10 total pectoral-fin rays. It was found in riffles, over gravel to stone bottom. 

Key words. Cobitoidei, Schistura, Laos, Mekong basin, stone loach



Diagnosis. Schistura thavonei is distinguished from the other species of the genus by its unique colour pattern made of two broad dark brown stripes (one middorsal, one midlateral) and between them a pale yellowish-brown stripe (iridescent copper to orange in life) from the upper extremity of the gill opening to the upper half of the base of the caudal fin; overimposed to the midlateral stripe, a row of 12–24 short black bars, located increasingly lower on the flank from head to tail, posterior-most ones restricted to the lower half of the body or forming blotches along the ventral midline of the caudal peduncle. Additional characters useful for identification but not unique to the species are: body very elongate (depth 6.2–7.2 times in SL), with a marked hump behind the head; male without suborbital flap; 8+7 branched caudal-fin rays; 7½ branched dorsal fin rays; 9–10 pectoral-fin rays.



Notes on biology. A dissected female (CMK 25066, 46.6 mm SL) had unripe ovaries with white, irregular, not mature, ova about 1.0 mm diameter. The stomach of a 42.4 mm SL specimen was filled with insect larvae about 2–5 mm long. Schistura thavonei was observed in clear water [as expected for a benthic fish with bright coloration and contrasted pattern]. At all sites, S. thavonei has been collected in stretches of streams with riffles (in the sheltered parts with somewhat quieter current), over gravel to stone bottom (Fig. 7).

Distribution. Schistura thavonei is presently known only from the watershed of the Nam Ma in Louang Namtha Province, a tributary of the Mekong, in northeastern Laos (not to be confused with the Nam Ma in Houa Phan Province, which flows to Vietnam and enters the Gulf of Tonkin).

Etymology. The species is named for Mr. Thavone Phommavong, in appreciation for his help and companionship during several, and sometimes difficult, fish surveys in Laos. A noun in genitive.



Maurice Kottelat. 2017. Schistura thavonei, A New Species of Loach from northwestern Laos (Teleostei: Nemacheilidae). RAFFLES BULLETIN OF ZOOLOGY. 65: 395–403

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