Glyptothorax coracinus, Ng & Rainboth, 2008

Ng, Heok Hee & Rainboth, Walter J., 2008, Glyptothorax coracinus, a new species of hillstream catfish from Cambodia (Teleostei: Sisoridae), Zootaxa 1839 (1), pp. 60-68 : 61-65

Glyptothorax coracinus sp. nov.

( Figs. 1 , 3a )

Type material. Holotype. UMMZ 248415 , 68.4 mm SL; Cambodia: Pursat, Ket River on road between Pramaoy and Thmor Da, 12°12'N 102°47'E; W. J. Rainboth et al., 24 February 2005.

Paratypes. UMMZ 246559 (1), 82.4 mm SL ; USNM 393557 (1), 65.9 mm SL; data as for holotype . UMMZ 243824 (1), 40.0 mm SL; Cambodia: Koh Kong, Areng River ; E. Rubidge et al., March 2004 .

Diagnosis. Glyptothorax coracinus can be distinguished from congeners except for G. siamensis in having a blackish brown body with indistinct pale longitudinal stripes on the lateral line and mid-dorsal regions. It differs from G. siamensis in having a smaller eye (6.3–7.2% HL vs. 7.5–11.2) and a thoracic adhesive apparatus with less convex lateral edges and in which anastomosing striae are absent (vs. present). Among congeners found in river systems draining mainland Southeast Asia, only G. interspinalus , G. laosensis , G. longicauda , G. longjiangensis , G. trilineatus and G. zanaensis have a color pattern consisting of a uniformly dark-colored body like G. coracinus . However, G. interspinalus , G. laosensis and G. trilineatus possess more distinct (and frequently broader) pale longitudinal stripes running along the lateral line and the mid-dorsal regions of the body. Glyptothorax coracinus can be distinguished from G. longicauda in having a shorter caudal peduncle (18.6–21.0% SL vs. 23.6) and fewer vertebrae (36–37 vs. 42), and from G. longjiangensis in having tubercles on the dorsal surface of the head with a single, median ridge (vs. with anastomosing tubercles with multiple ridges) and without any pale markings on the nuchal plate (vs. part or all of the nuchal plate pale-colored). It differs from G. zanaensis in having a shorter adipose-fin base (12.3–14.5% SL vs. 14.4– 18.4), smaller eye (6.3–7.2% HL vs. 8.9–11.0) and a less posteriorly-extended thoracic adhesive apparatus (not reaching to level of base of last pectoral-fin ray vs. reaching beyond). Glyptothorax coracinus is additionally distinguished from G. interspinalus in having a smaller eye (6.3–7.2% HL vs. 8.3–14.7) and deeper caudal peduncle (7.9–9.4% SL vs. 6.1–7.0), from G. laosensis in having a smaller eye (6.3–7.2% HL vs. 8.6– 11.1) and a less posteriorly-extended thoracic adhesive apparatus (not reaching to level of base of last pectoral-fin ray vs. reaching beyond), and from G. trilineatus in having a longer caudal peduncle (18.6–21.0% SL vs. 16.7–18.4).

Description. Morphometric data as in Table 1. Body subcylindrical. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile flat to anal-fin base, then sloping gently dorsally from anal-fin base to end of caudal peduncle. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Skin tuberculate, with small tubercles on sides of body. Lateral line complete and midlateral. Vertebrae 6+20=36 (1) or 17+20=37* (3).

Head depressed and broad, triangular when viewed laterally. Snout prominent. Anterior and posterior nares large and separated only by base of nasal barbel. Gill openings broad, extending from directly beneath post-temporal to isthmus. Bony elements of dorsal surface of head covered with thick, tuberculate skin. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head.

Barbels in four pairs. Maxillary barbel long and slender, extending to middle of pectoral-fin base. Nasal barbel slender, extending to four fifths of distance between its base and anterior orbital margin. Inner mandibular barbel origin close to midline, extending to midway between its base and that of pectoral spine. Outer mandibular barbel originating posterolateral of inner mandibular barbel, extending to four fifths of distance between its base and that of pectoral spine.

Mouth inferior, premaxillary tooth band partially exposed when mouth is closed. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary teeth in single broad semilunate band. Dentary teeth in two narrow crescentic bands separated at midline.

Dorsal fin located above anterior third of body, with I,6 (4) rays; fin margin convex; spine short and straight, smooth on anterior and posterior margins. Adipose fin with anterior margin straight or very slightly concave and posterior margin angular. Caudal fin strongly forked, with lower lobe very slightly longer than upper lobe and i,6,7,i* (1) or i,7,7,i (3) principal rays. Procurrent rays symmetrical and extending only slightly anterior to fin base. Adipose-fin origin at vertical through base of first anal-fin ray. Anal fin with straight anterior margin and straight or slightly concave posterior margin; with iv,8* (2) or iv,10 (2) rays. Pelvic-fin origin at vertical through posterior end of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (4) rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,9,i (4) rays; posterior fin margin slightly concave; anterior spine margin smooth, posterior margin with 7–11 (holotype =10) serrations.

Thoracic adhesive apparatus present, consisting of ridges of skin in an elongate oval field extending from isthmus to just anterior to level of last pectoral-fin base. Median depression present on posterior third of adhesive apparatus. Ridges uninterrupted and oriented anterodistally, radiating from median depression.

Coloration. In 70% ethanol: Dorsal and lateral surfaces of head, and body dark brown, fading to beige on ventral surfaces. A faint thin, lighter brown mid-dorsal stripe extending from base of last dorsal-fin ray to origin of adipose fin; stripe very faint in some individuals. Laterosensory pores along lateral line rimmed in beige, imparting appearance of a diffuse lighter brown midlateral line. All fins with brown fin rays, and diffuse melanophores on fin membranes. Pectoral and pelvic fins with brown on bases of fin rays and hyaline posterior margin. Anal fin with brown base and hyaline posteroventral corner. Adipose fin brown, with hyaline distal margin. Caudal fin brown, with tips of lobes hyaline. Maxillary and nasal barbels brown dorsally, beige ventrally. Mandibular barbels beige.

Distribution. Glyptothorax coracinus is known only from the short coastal drainages draining the western face of the Krâvanh (Cardamom) Mountains and Dâmrei (Elephant) Mountains in southwest Cambodia ( Fig. 2 ).

Etymology. The specific epithet comes from the Greek korakinos, meaning like a raven, an allusion to the dark coloration of this species.

Figures

FIGURE 1. Glyptothorax coracinus, holotype, UMMZ 248415, 68.4 mm SL; Cambodia: Ket River.

FIGURE 2. Map showing collecting localities of Glyptothorax coracinus.

FIGURE 3. Thoracic adhesive apparatus of: a. G. coracinus, UMMZ 248415, holotype, 68.4 mm SL; b. G. laosensis, ZFMK 24328, 75.5 mm SL; c. G. siamensis, CMK 12874. 75.0 mm SL. Illustrations not to scale.