Pseudecheneis gracilis, Zhou & Li & Yang, 2008

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 : 111-113

Pseudecheneis gracilis , new species

( Fig. 7 )

Pseudecheneis sulcatus – Chu, 1982: 431 (in part specimens from Irrawaddy); Chu, Mo & Kuang, 1990: 196–197, Fig. 196 (in part specimens from Irrawaddy) ; Chu & Mo 1999: 153–154, Fig. 98 (in part specimens from the Irrawaddy) .

Material examined. – Holotype. SWFC 200102125, 201 mm TL, 168 mm SL; Qushi (25 ° 14'N 98 ° 36.43'E) at the upper of Longchuanjiang (branch of Irrawaddy River ), Tengchong County, Yunnan Province; Y.-W. Zhou & X.-F. Pan, 24 Feb.2001.

Paratypes. – SWFC 200102127–128, 200102135–138, 200102140, 200102148, 8 ex., 76–226 mm TL, 62–188 mm SL (1 DS), same date as holotype. SWFC 200101665–667, 3 ex., 69– 162 mm TL, 56–134 mm SL; Daju (25 ° 06.97'N 98 ° 35.63'E) at a branch of the upper Longchuanjiang , Tengchong County, Yunnan Province; J.-L. Lu, 21 Jan.2001 .

Diagnosis. – Pseudecheneis gracilis is distinguished from P. sulcata in having longer pelvic fin, reaching base of first anal fin ray (vs. not reaching), and from P. crassicauda in having longer pectoral fin, reaching origin of pelvic fin (vs. not reaching). Pseudecheneis gracilis is further distinguished from P. serracula in having a shorter adipose fin base (length of adipose fin base 125–166.7% in length of anal fin base vs. larger than 200%), and from P. sympelvica in having separate pelvic fins (vs. fused). It can be distinguished from other congeners except P. immaculatus in having a long caudal peduncle (27.5–35.8% SL vs. 20.4–28.3), and further differs from other congeners except P. stenura in having deeper forked of caudal fin, the shortest ray of caudal fin circa 50% of longest ray (vs. 75%). Pseudecheneis gracilis is distinguished from P. immaculatus in having shorter pectoral fin (27.1–30.6% SL vs. 29.4–38.3), and having yellow spots and patches on the body (vs. lacking). Pseudecheneis gracilis differs from P. stenura in having a saddle patch at dorsal fin origin (vs. two ovoid, isolated yellow patches on lateral of dorsal fin origin) ( Fig. 5B, C ) and further in having shorter head length (head length 14.9– 18.6% SL vs. 20.1–23.7, postorbital head length 4.5–5.9% head length vs. 8.5–11.4, body depth 73.9–112.2% head length vs. 67.1–88.5).

Description. – Morphometric data as in Table 1. Body elongate. Dorsal profile rising gradually from tip of snout to origin of dorsal fin, then sloping slowly ventrally to end of caudal peduncle. Head and abdominal region before origin of pelvic fin moderately broad. Body after dorsal fin compressed gradually. Caudal peduncle long and moderately compressed. Thoracic adhesive apparatus oval with 16–20 transverse ridges (laminae).

Head compressed and broadly rounded when viewed from above. Eye small and almost rounded, subcutaneous and located on dorsal surface of head. Distance to tip of snout longer than to dorsalmost extremity of gill openings. Mouth small, transverse and inferior. Lips with papillae. Premaxillary tooth band semicircular and two or four teeth along its outer edge ( Fig. 2A ). Mandibular tooth band crescent ( Fig. 2B ). Outer teeth shovel-shaped ( Fig. 3A–C ). Inner teeth conical ( Fig. 3D–F ). Teeth on premaxillary and mandibular tooth bands sparse and embedded in skin. Only tips exposed and arranged in irregular rows. Barbels flattened and in four pairs with papilla except nasal barbel. Nasal barbel short, not extending to orbit. Maxillary barbel not

THE RAFFLES BULLETIN OF ZOOLOGY 2008

developed, only extending to level of anterior orbit margin and not reaching gill opening. Length of outer mandibular barbel longer than inner mandibular barbel, not reaching or just beyond the front of thoracic apparatus. Gill openings moderate, extending beyond base of first pectoral fin element.

First and second unbranched ray of dorsal fin not ossified. Dorsal fin post-dorsal margin concave slightly. Dorsal fin origin located at point through anterior third of body, distance of dorsal fin base to origin of adipose fin longer than distance to front of orbit. Adipose fin origin at vertical through anal fin origin. Length of adipose fin base shorter than distance of its origin to end of dorsal fin base. Pectoral fin enlarged with concave posterior margin, extending beyond origin of pelvic fin and not to end of pelvic fin base. Origin of pelvic fin at vertical through preceding end of dorsal-fin base. Pelvic fin extending to anus. First unbranched ray of paired fin broadened with regular striae on ventral surface. Anal fin post-ventral margin emarginate. Distance of anal fin origin to caudal fin base larger than to base of pectoral fin. Anus and urogenital openings located at origin of anal fin. Shortest ray of caudal fin circa 50% of longest ray. Upper lobe shorter than lower lobe.

Body covered with dense, rounded tubercles distributed irregularly, not uniformly ( Fig. 4A ). Tubercles decreasing in density gradually from occipital to caudal peduncle which almost no tubercles.

Lateral line complete and midlateral. Vertebrae 19+19=38 (1).

Colouration. – Alive, chestnut brown on dorsal and lateral surfaces of head and body. Light yellow on ventral region. Pink thoracic apparatus and oral region. Occipital having an obvious, small, yellow, triangular patch. Post-temporal having a small yellow ovate spot. Dorsal fin origin and end of base respectively having a yellow saddle patch ( Fig. 5B ). Before origin of adipose fin with three yellow patches. Median patch just located at origin of adipose fin. Two lateral patches extending vertically to lateral line. An ovate patch on posterior end of adipose fin base. Another on base of caudal fin.

Etymology. – From the Latin gracil, meaning long and slender, in reference to head smallish making body elongate and tenuous. Used as an adjective.

Figures

Fig. 7. Pseudecheneis gracilis, SWFC 200102125, holotype, 168 mm SL; China: Longchuanjiang (a branch of Irrawaddy River drainage). Dorsal, lateral and ventral views.

Fig. 5. Patch or spots at dorsal fin origin: A, spots connected as a saddle patch (Pseudecheneis brachyurus, SWFC 200103294, holotype, 122 mm SL); B, spots connected as a saddle patch (P. gracilis, SWFC 200102125, paratype, 168 mm SL); C, spots isolated as two ovoid spots (P. stenura, SWFC 0502001, 90.5 mm SL).

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. 3. Tooth shape of premaxillary tooth band (Pseudecheneis gracilis, SWFC 200102148, paratype, 68 mm SL, DS): A–C, outer teeth; D–F, inner teeth. A, D, lateral view; B, E, frontal view; D, F, frontal-lateral view.

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).