Sinogastromyzon nantaiensis

Chen, Han & Fang, 2002

Order: Cypriniformes
Family: Balitoridae  
Subfamily: Balitorinae
Genus: Sinogastromyzon

Environment: Freshwater; demersal
Climate: Subtropical

Description. D. iii, 8-9; A. iii, 5; P. xi-xiii, 13-15; V. vi-x, 15-17; l. lat. 50-53; predorsal scales 16-17. Vertebrae 32. Dorsal fin with 3 simple and 8-9 branched rays (mode 8). Anal fin with 2 simple and 5 branched rays. Pectoral fin with 10-13 simple (mode 11) and 13-15 branched rays (mode 14) (total 24-27; usually 25-26). Ventral fin with 6-10 simple (mode 7) and 15-17 branched rays (mode 16) (total 21-25, mode 23). Body and head very strongly dorso-ventrally compressed as anteriorly 2/3 region. Caudal very short, stout and compressed. Ventral profile completely flat. Head strongly dorso-ventrally compressed and rounded in dorsal view. Dorsal half of head densely covered with tiny sharp papillae. Upper lip with a single series of 14-17 small rounded papillae, with no distinct papillae on lower lip. Four rostral barbels and two barbels at both corners of mouth. Origin of dorsal fin slightly behind origin of pelvic fin. Pectoral fin very large, length longer than head length.  Ventral fin base close together and with complete connecting membrane as a suckig disc. Posterior margin of ventral fin extending beyond dorsal-fin origin and beyond anus and even beyond anal-fin origin in some adults. Caudal fin forked, lower lobe slightly longer than upper one. Dorsal part of body with small cycloid scales, ventral region between pectoral and pelvic fins naked. Body uniformly olive brown; predorsal region of dorsum uniform in adults, with irregularly rounded dark brown blotches in smaller sub-adults, dorsal side with irregularly rounded dark brown blotches. Pectoral fin brown without any dark marks. Caudal fin greyish black with two vertically light grey stripes.

Distribution: Asia: Kaoping and Tzengwen River basins (including Chiaryi, Tainan, Kaohsiung and Pingtung counties)  in southern Taiwan.

EcologySinogastromyzon nantaiensis occurs in very swift current of middle and lower reaches of river basins and can tolerate the slightly higher water temperature. Is always found in riffles at altitudes below 500 m. The body shape is well adapted to torrential flow in the riffles and runs among rocky substratum. It feeds mainly on tiny aquatic invertebrates, sedimentary detritus or fragile organic debris and prefers very clear water with low tolerance to the increased sediment load in waters.

Remarks. This endemic species, just described recently (Chen et al., 2002). In Taiwan, Sinogastromyzon nantaiensis is differentiated from the closely related S. puliensis by having fewer lateral-line scales (49-53, vs. 60-65), fewer predorsal scales (16-17, vs. 23-25), and pectoral fin base unmarked (vs. with many brown spots). This species generally distinguished from S. puliensis by their small adult size (mean 35.1-44.2 cm SL).

Material examined: Holotype. NMMBP 00465, 44.7 mm SL; Taiwan: Pingtung County: Liukuei, Darjin, Kaoping basin,  Laonon River; Aug. 1994, I-S. Chen et al.

Paratypes. NMMBP 00466, 3, 36.8-40.3 mm SL, same data as holotype. – NMMBP-00467, 7, 33.4- 44.2 mm SL; Taiwan: Pingtung County: Lukuei, Tsaolan, Kaoping basin, Laonon River; Feb. 1995, I-S. Chen et al. – NMMBP 00468, 2, 29.8-35.6 mm SL; Taiwan: Tainan County: Peiliao, Tzengwen River, Nanhaur River; Oct. 29, 1999, I-S. Chen & R.-S. Wu.