Pseudecheneis immaculatus Chu, 1982

Zhou, Wei, Li, Xu & Yang, Ying, 2008, A Review Of The Catfish Genus Pseudecheneis (Siluriformes: Sisoridae) From China, With The Description Of Four New Species From Yunnan, Raffles Bulletin of Zoology 56 (1), pp. 107-124 : 113

Pseudecheneis immaculatus Chu, 1982

( Fig. 8 )

Pseudecheneis immaculatus Chu, 1982: 428 , Fig. 1 (Weixi, Deqin); Chu, Mo & Kuang, 1990: 198–199, Fig. 198 (Weixi, Deqin); Chu & Mo 1999: 154–155, Fig. 99 (Weixi, Deqin); Thomson & Page, 2006: 60 (Mekong drainage, China).

Material examined. – Lancangjiang (Mekong River) drainage: KIZ 748742 1 ex., holotype, 96mm SL, KIZ 748650–652 , 748735–739 , 748741 , 9 ex., paratypes, 72.8–104mm SL, Baijixun , Weixi County, Yunnan Province ; KIZ 748636–748640 , 5 ex., paratypes, 74.5–89.2mm SL, Liutongjiang , Deqin County, Yunnan Province ; SWFC 9908007, 0004081–085, 0004095, 7 ex., 76.5–102.5 mm SL (1 DS), Liutongjiang , Deqin County, Yunnan Province .

Morphometric data as in Table 2.

Diagnosis. – Pseudecheneis immaculatus is distinguished from all other congeners in lacking yellow spots or patches on the body (vs. having). Distinguished from all congeners except P. longipectoralis in having longer pectoral fin, extending to pelvic fin base (vs. not extending). It differs from P. longipectoralis in having a longer caudal peduncle (28.2–32.9% SL vs. 24.9–28.2). Premaxillary tooth band semicircular with two or four teeth along outer edge ( Fig. 2A ). Body covered with dense, tubercles distributed uniformly, some longitudinal tubercles among rounded tubercles ( Fig. 4B ). Vertebrae 18+17=35 (1).

Distribution. – This species is found in the main river and branches of middle and upper Lancangjiang ( Fig. 6).

Dorsal fin hyaline, with a thin chestnut brown band near distal margin of fin and a small yellow patch on tip. Adipose fin chestnut brown, with lighter colour around distal edge. Caudal fin base brown. Upper and lower edges with lightyellow lateral stripe near caudal fin base. Two light-yellow patches on forked median distal margin of caudal fin and yellow patch on tip of each lobe. Anal fin hyaline, base dark brown. Middle to distal margin light yellow with a dark strip. Dorsal surfaces of pectoral fins brown. Yellow elliptical patch near base. Yellow patch near distal margin. Pelvic fin base brown and other part light yellow.

Distribution. – This species is found in the upper Longchuanjiang, belonging to Irrawaddy River drainage ( Fig. 6).

Figures

Fig. 8. Pseudecheneis immaculatus, KIZ 748742, holotype, 96 mm SL; China: Lancangjiang (the upper Mekong River) drainage. Dorsal, lateral and ventral views.

Fig. 2. Premaxillary and mandibular tooth band. A, ventral view of semicircular premaxillary tooth band and four teeth along its outer edge (Pseudecheneis gracilis, SWFC 200102148, paratype, 68 mm SL, DS); B, dorsal view of crescent mandibular tooth band (P. gracilis, SWFC 200102148, paratype, 68 mm SL, DS); C, ventral view of semicircular premaxillary tooth band and eight teeth along its outer edge (P. paviei, SWFC 0005084, 62 mm SL, DS).

Fig. 4. Tubercles at dorsal of head: A, rounded tubercles (Pseudecheneis stenura, SWFC 0502004, 78.6 mm SL); B, some longitudinal tubercles among rounded tubercles (P. sulcatoides, SWFC 200005030, 75 mm SL).