Pseudexostoma brachysoma Chu, 1979

Zhou, Wei, Yang, Ying, Li, Xu & Li, Ming-Hui, 2007, A Review Of The Catfish Genus Pseudexostoma (Siluriformes: Sisoridae) With Description Of A New Species From The Upper Salween (Nujiang) Basin Of China, Raffles Bulletin of Zoology 55 (1), pp. 147-155 : 148-150

Pseudexostoma brachysoma Chu, 1979

( Figs. 1 , 2A , 3A , 4)

Pseudexostoma yunnanensis brachysoma Chu, 1979: 78–79 (Laowo, Yunlong County) ; Chu, Mo & Kuang, 1990: 214–215, Fig. 215 (Laowo, Yunlong County); Chu & Mo, 1999: 179–180, Fig. 118 (Laowo, Yunlong County).

Material examined. – Topotypes: SWFC 9910007, 9910015, 2 ex., 85 mm TL, 72–75 mm SL, Laowo , Lushui County, Yunnan Province ; SWFC 200103328-344, 200103352–367, 33 ex., 60–135 mm TL, 52–119 mm SL, Laowo , Lushui County, Yunnan Province . Other materials: SWFC 200102025–031, 200102041–045, 200102053–054, 200102056, 15 ex., 111-152 mm TL, 95–142 mm SL, Xiangda , Longling County, Yunnan Province ; SWFC 9910074– 080, 7 ex., 97–134 mm TL, 85–115 mm SL, Gudeng , Lushui County, Yunnan Province ; SWFC 9910022–033, 9910035–38, 9910044– 057, 30 ex., 61–153 mm TL, 52-135 mm SL, Muna , Fugong County, Yunnan Province ; SWFC 200106001, 1 ex., 124 mm TL, 103 mm SL, Daxingdi , Lushui County, Yunnan Province ; SWFC 200411001–002, 2 ex., Liuku , Lushui County, Yunnan Province .

Diagnosis. – Pseudexostoma brachysoma is distinguished from P. yunnanensis by the following combination of characteristics: posterior margin of lower lip with three notches, depth of middle notch shallower than lateral ones (vs. as the same depth), length of two smaller median lobes of lower lip longer than lateral lobes ( Fig. 2A ) (vs. as the same length, Fig. 2C ); pelvic fin i, 3–4 (vs. i, 5); base of adipose fin longer (36.1–46.0% SL vs. 28.8–39.8); caudal peduncle more slender (depth of caudal peduncle 4.2–6.9% SL and 20–33.7% in length of caudal peduncle vs. 6.4–8.3 and 32.6–42.7); premaxillary tooth band with 16-18 teeth (vs. 18–22), premaxillary tooth band divided into two and isolated ( Fig. 3A ) (vs. connected partially, Fig. 3C ). Pseudexostoma brachysoma differs from P. longipterus in having a shorter pectoral fin, pelvic fin and caudal fin (pectoral fin 24.9–29.8% SL vs. 30.1–31.3, pelvic fin 16.1–22.9% SL vs. 23.1–24.3, caudal fin 13.6–17.9% SL vs. 18–19.6), smaller eyes and a narrower interorbital width (eye diameter 5.8–7.8% HL vs. 8.2–10, interorbital width 19.7–24.7% HL vs. 25.5–30.8).

Description. – Morphometric data as in Table 1.

Body moderately compressed. Dorsal profile rising evenly and somewhat steeply from tip of snout to origin of dorsal fin, then sloping gently ventrally to end of caudal peduncle. Head and abdominal region before origin of anal fin broad and flat. Body after adipose fin compressed gradually.

Head depressed and broad, triangular when viewed laterally and with rounded snout when viewed from above. Eye small and ovoid, subcutaneous and located at middle of dorsal surface of head. Mouth transverse and inferior, premaxillary and mandibular tooth bands exposed when mouth closed. Teeth embedded in skin, shovel-shaped, tips exposed and arranged in irregular rows. Premaxillary tooth band divided into two, with 16–18 teeth ( Fig. 3A ). Anterior nostril tubular, separated from posterior nostril by nasal barbel base. Gill opening narrow, extending from one-third of last ray of pectoral fin to the first ray. Dorsal surface smooth without tubercles. Barbels in four pairs. Maxillary barbel flattened, with surrounding flap of skin and rounded tip, extending beyond pectoral fin origin, but not reaching to gill opening and far from posttemporal. Nasal barbel with small flap of thin skin fringing posterior margin and not reaching anterior margin of orbital. Post labial groove connected. Lower lip broad with three notches along posterior margin, divided into two bigger lateral lobes and two smaller median lobes. Depth of middle notch shallower than depth of lateral side notches. Two smaller median lobes of lower lip longer than lateral lobes. Inner mandibular-barbel close to midline, extending to pectoral fin origin. Outer mandibular-barbel precedes lateral inner mandibular barbel, extending to pectoral fin origin ( Fig. 2A ).

Unbranched dorsal fin rays not ossified. Post-dorsal margin of dorsal fin concave slightly. Origin of dorsal fin located at point through anterior third of body. Adipose fin base not connected with caudal fin. Caudal fin emarginate, upper lobe smaller than lower lobe. Anal fin post-ventral margin emarginate. Distance of anal fin origin to caudal fin base shorter than to end of pelvic fin base. Origin of pelvic fin precedes vertical end of dorsal fin base. Pelvic fin margin convex slightly, not extending to anus. Pectoral fin greatly enlarged and first unbranched ray not ossified. First unbranched ray of paired fins broadened with regular striae on ventral surface. Anus and urogenital openings located at end of pelvic fin and before origin of anal fin. Lateral line midlateral and complete.

Coloration. – Grey black on dorsal surface without spots or patches. Grey yellow on ventral region. Caudal fin grey black with an irregular, small, yellow patch in the middle. Fins with grey yellow around distal edge.

Distribution. – Only known from the middle and lower Nujiang basin ( Fig. 4).

Remarks. – “Laowo”, the type locality of Pseudexostoma yunnanensis brachysoma Chu , belonged to Yunlong County of Dali Prefecture, Yunnan and now it belongs to Lushui County of Nujiang Prefecture, Yunnan. After comparing morphological characters, the results show that there are distinct differences between the topotypes of P. yunnanensis brachysoma Chu and specimens of Pseudexostoma yunnanensis yunnanensis (Tchang) in the structure of their lower lobe, shape of premaxillary tooth band, number of branched pelvic fin rays and meristic and mensural characteristics. So they should be given species status instead of subspecies status.

Figures

Fig. 1. Pseudexostoma brachysoma, SWFC 9910051, 118 mm SL; China: Nujiang (the upper Salween River) drainage. Dorsal, lateral and ventral views.

Fig. 2. Ventral view of lower lip. A–B, depth of middle notch shallower than depth of lateral ones, and length of two smaller median lobes of lower lip longer than lateral lobes (A, P. brachysoma, SWFC 9910051, 118 mm SL; B, P. longipterus, SWFC 200308022, holotype, 82.1 mm SL); C, Depth of middle notch the same as depth of lateral ones, and length of two smaller median lobes of lower lip the same as lateral lobes (P. yunnanensis, SWFC 200102201, 111 mm SL).

Fig. 3. Ventral view of premaxillary tooth band. A–B, Premaxillary tooth bands isolated (A, P. brachysoma, SWFC 200103329, 107 mm SL; B, P. longipterus, SWFC 200308022, holotype, 82.1 mm SL); C, Premaxillary tooth bands connected partially (P. yunnanensis, SWFC 200102178, 108 mm SL).