Pseudecheneis maurus, Ng, Heok Hee & Tan, Heok Hui, 2007

Ng, Heok Hee & Tan, Heok Hui, 2007, Pseudecheneis maurus, a new species of glyptosternine catfish (Teleostei: Sisoridae) from Central Vietnam, Zootaxa 1406, pp. 25-32 : 26-29

Pseudecheneis maurus sp. nov.

( Fig. 1 )

Type material. Holotype: ZRC 50638, 54.8 mm SL; Vietnam: Da Nang province, Song Thuy Loan drainage, Ban Na hill station, Cat Lon stream, ca. 9 km along road before summit, 16°0'39.2"N 108°1'2.6"E, 722 m asl; H. H. Tan & A. D. Tran, 28 February 2005.

Diagnosis. Pseudecheneis maurus is distinguished from all congeners in having a shorter adipose-fin base (1.2 times length of anal-fin base vs. 1.5–2.0 times; 15.7% SL vs. 17.6–30.6), (except for P. sympelvica ) thoracic adhesive apparatus with sulcae not meeting (vs. meeting) at midline and (except for P. immaculata ) in lacking (vs. having) distinct pale spots on the body It further differs from P. immaculata in having a shorter pectoral fin (24.3% SL vs. 32.0) and shorter and deeper caudal peduncle (length 21.2% SL vs. 28.8; depth 6.0% SL vs. 4.0). from. It differs from P. p a v i e i and P. sympelvica in having an elongate body with 38 vertebrae (vs. short body with 33–35 vertebrae) and from P. sympelvica in having separate (vs. fused) pelvic fins.

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 19+19=38.

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 13 transverse ridges (laminae) separated by grooves (sulcae); sulcae not meeting at midline of adhesive apparatus. Adhesive apparatus extending from immediately posterior to collar on distal margin of branchiostegal membrane to immediately posterior to level of last pectoralfin 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 originating 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.

Holotype

%SL

Predorsal length 35.8 Preanal length 64.8 Prepelvic length 41.1 Prepectoral length 17.9 Length of dorsal-fin base 11.9 Anal-fin length 13.9 Pelvic-fin length 20.4 Pectoral-fin length 24.3 Caudal-fin length 23.9 Length of adipose-fin base 15.7 Dorsal to adipose distance 19.9 Post-adipose distance 17.5 Caudal peduncle length 21.2 Caudal peduncle depth 6.0 Body depth at anus 11.1 Head length 22.4 Head width 18.1 Head depth 13.9 %HL

Snout length 59.3 Interorbital distance 26.8 Eye diameter 10.6 Nasal barbel length 31.7 Maxillary barbel length 61.8 Inner mandibular barbel length 26.8 Outer mandibular barbel length 48.8 Dorsal-fin origin located at point through anterior third of body. First and second dorsal fin-ray elements not ossified, bearing i,6 rays, and fin margin straight. Adipose fin with very short base, 1.2 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 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 iii,7,i 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 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 rays.

Coloration. In 70% ethanol: chestnut brown on dorsal and lateral surfaces of head and body, fading to light brown on ventral region. Dorsal surfaces of head and body with indistinct light brown patches on supraoccipital spine and immediately anterior to dorsal-spine base. Lateral surfaces of body with very faint light brown patches: one patch immediately posterior to last dorsal-fin ray and an elongate ovate spots on side of body immediately ventral to origin of adipose fin. Dorsal and anal fins with chestnut brown base and subdistal band. Adipose fin chestnut brown, with light brown anterior margin and margin along posterior twothirds of fin. Caudal fin chestnut brown, with small hyaline spot on lobes near horizontal midline and hyaline distal margin. Dorsal surfaces of pectoral and pelvic fin bases chestnut brown, with hyaline distal margin; ventral surfaces hyaline. Maxillary and nasal barbels chestnut brown dorsally and light brown ventrally.

Distribution. Presently known only from the Song Thuy Loan River drainage (of which the Cat Lon stream is a tributary) that drains the eastern face of the Annam Cordillera in central Vietnam ( Fig. 2 ).

Habitat. The single specimen was obtained from a riffle zone of a small hill stream (ca 2–4 m wide, ca 10–30 cm deep). The bottom consists of fine gravel and granitic rocks, with exposed boulders along the banks and streamline ( Fig. 3 ). The water was swift flowing and cool (ca 24 °C). No other fish were obtained from this habitat, although at least six species of amphibian tadpoles were present (unpub. data).

Etymology. From the Greek mauros, meaning dark, in reference to the absence of distinct pale spots on the body of this species. Used as a noun in apposition.

Figures

FIGURE 1. Pseudecheneis maurus, ZRC 50638, holotype, 54.8 mm SL; Vietnam: Cat Lon stream. Dorsal, lateral and ventral views.

FIGURE 2. Map showing type locality of Pseudecheneis maurus (indicated by solid triangle).

FIGURE 3. Photograph of Cat Lon stream, type locality of Pseudecheneis maurus.