Pseudecheneis suppaetula, Heok Hee Ng, 2006

Heok Hee Ng, 2006, Pseudecheneis suppaetula, a new species of glyptosternine catfish (Teleostei: Sisoridae) from India., Zootaxa 1267, pp. 59-68 : 60-65

Pseudecheneis suppaetula sp. nov.

(Fig. 1)

Pseudecheneis sulcata (non M’Clelland, 1842)-Kullander et al., 1999: 153.

Type material

Holotype: NRM 36977 , 84.1 mm SL; India: Himachal Pradesh, Ganges River drainage, upper reaches of Giri River, in Chhaila area (in the vicinity of Kotkhai) , 31°6'15"N 77°25'56"E; E. Åhlander et al., 3 November 1997.

Paratypes: NRM 36968 (1), 41.3 mm SL ; NRM 36974 (2), 66.6-77.5 mm SL; data as for holotype.

Diagnosis

Pseudecheneis suppaetula is distinguished from P. paviei and P. sympelvica in having an elongate body with 37-38 vertebrae (vs. short body with 33-35 vertebrae) and from P. sympelvica in having separate (vs. fused) pelvic fins. It differs from other congeners (except P. immaculata and P. serracula ) in having a longer adipose-fin base (at least 2.0 times length of anal-fin base vs. 1.5-2.0 times; 26.6-30.6% SL vs. 17.8-24.3) and (except for P. crassicauda and P. immaculata ) in having a smaller eye (8.1-8.3% SL vs. 8.8-12.8). Pseudecheneis suppaetula is distinguished from P. immaculata in the presence (vs. absence) of pale spots on the body, and from P. serracula in having a smaller eye (8.1-8.3% HL vs. 9.1-12.2) and the neural spines of the last 2-3 preanal and first 6-7 postanal vertebrae gradually increasing in height (vs. neural spines of corresponding pre- and postanal vertebrae strongly elevated; Fig. 2).

Description

Biometric data as in Table 1. Head and abdominal region narrow and strongly depressed. Dorsal profile rising gently from tip of snout to origin of dorsal fin, then almost horizontal or sloping very gently ventrally to end of caudal peduncle. Ventral profile horizontal to anal-fin base, then sloping very gently dorsally to end of caudal peduncle. Caudal peduncle long and moderately compressed. Anus and urogenital openings located at posteriormost extent of pelvic fin. Skin smooth, tuberculate in some areas. Lateral line complete and midlateral. Vertebrae 18+19=37* (3) or 19+19=38 (1).

Head acutely rounded when viewed from above. Gill openings moderate, extending from posttemporal region to base of first pectoral-fin element. Head covered with thick, tuberculate skin. Ventral surface of head with unculiferous collar on distal margin of branchiostegal membrane immediately anterior to thoracic adhesive apparatus.

Thoracic adhesive apparatus consisting of 11-13 transverse ridges (laminae) separated by grooves (sulcae); ridges sometimes not meeting at midline of adhesive apparatus. Adhesive apparatus extending from immediately posterior to collar on distal margin of branchiostegal membrane to level of last pectoral-fin ray.

Barbels flattened, and in four pairs. Maxillary barbel with ventral surface densely covered with papillae, and pointed tip; barbel extending about two-thirds of distance between its base and base of first pectoral-fin element. Distal half of barbel attached to snout via large, thin flap of skin. Nasal barbel with small flap of thin skin fringing posterior margin and extending midway to distance between posterior nares and anterior orbital margin. Inner mandibular-barbel densely covered with papillae; origin close to midline, extending to collar on distal margin of branchiostegal membrane. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to level of anterior orbital margin. Eye small and almost rounded, subcutaneous and located on dorsal surface of head.

Mouth inferior, with moderately broad, thin papillate lips. Rictal lobe large and papillate. Premaxillary tooth band not exposed when mouth is closed. Premaxillary teeth short and conical, arranged in irregular rows on a moderately large quadrangular patch. Dentary teeth long, thin and somewhat rounded at tip; arranged in irregular rows on two separated, roughly triangular patches.

Dorsal-fin origin located at point through anterior third of body. First and second dorsal fin-ray elements not ossified, bearing i,6 (4) rays, and fin margin straight. Adipose fin with moderately long base, at least 2.0 times anal-fin base length; located in middle third of postdorsal region. Adipose fin margin gently convex; posterior end deeply incised. Caudal fin forked, with i,7,8,i (4) principal rays; procurrent rays symmetrical and extend only slightly anterior to fin base. Anal fin with short base extending less than half of adipose fin-base length and iv,6 (2), iv,7 (1) or iv,8* (18) rays. Anal fin margin almost straight.

Pelvic-fin origin at vertical through second or third dorsal fin-ray base. Pelvic fin greatly enlarged, extending to base of first anal-fin ray. Anterior fin margin strongly convex, first element broadened and with regular striae on ventral surface; with i,5 (4) rays. Pectoral fin greatly enlarged and with convex anterior margin, reaching to just beyond pelvic-fin base. First element not ossified, broadened and with regular striae on ventral surface; fin with i,11,i (4) rays.

Coloration

In 70% ethanol: grayish brown on dorsal and lateral surfaces of head and body, fading to light brown on ventral region. Dorsal surfaces of head and body with distinctive series of small light brown spots: one spots on supraoccipital region; a pair on either side of body on supratemporal region; one papillon-shaped spot on base of first dorsal-fin ray, and another immediately posterior to last dorsal-fin ray; a pair of elongate ovate spots on sides of the body immediately ventral to origin of adipose fin, another chevron-shaped spot at posterior end of adipose fin. Posterior end of caudal peduncle with a pair of ovate spots: one dorsal and one ventral; spots coalesce with corresponding spots on other side of body along dorsal and ventral midlines. Dorsal and anal fins light brown, with grayish brown base and subdistal band. Adipose fin light grayish brown, with light brown ovate spot at origin and light brown distal margin along posterior two-thirds of fin, coalescing with chevron-shaped spot on body at posterior extremity of fin. Caudal fin grayish brown, with light brown band on middle third of fin. Dorsal surfaces of pectoral and pelvic fins grayish brown, with light brown distal margin; ventral surfaces light brown. Maxillary and nasal barbels grayish brown dorsally and light brown ventrally.

Distribution

Presently known only from the Ganges River drainage in Himachal Pradesh, India (Fig. 3).

Habitat and ecology

The type locality was a wide (ca. 20 m), shallow (1 m) river with a rocky/sandy bottom. The water was clear and swift-flowing. Other fish species collected at this locality were Schizothorax richardsonii (Cyprinidae), Tor chelynoides (Cyprinidae), Schistura montana (Balitoridae), and Glyptothorax pectinopterus (Sisoridae).

Etymology

From the Latin suppaetulus, meaning squinting somewhat, in allusion to the small eye of this species. Used as an adjective.

Discussion

The relatively long adipose-fin base of P. suppaetula easily distinguishes it from congeners. Only P. immaculata and P. serracula have adipose-fin bases that are as long, but they can be distinguished from P. suppaetula by the characters mentioned in the diagnosis. Externally, P. suppaetula most resembles P. serracula , a species also found in the Ganges River drainage. However, in addition to the larger eye of P. serracula when compared to P. suppaetula , the strongly elevated neural spines of P. serracula impart a noticeably hunched appearance to this species (as pointed out by Ng & Edds, 2005) when compared to P. suppaetula .

There are apparently fewer transverse ridges (laminae) in the thoracic adhesive apparatus of P. suppaetula (11-13) when compared to P. serracula (13-18). However, with only four specimens of the former species, the variation in this number is not well understood. The difference in the eye diameter between P. serracula and P. suppaetula is not due to ontogeny. A biplot of eye diameter for P. suppaetula vs. P. serracula (Fig. 4) shows that the regression lines are significantly different (ANCOVA; P<0.05).