Glyptothorax filicatus, Ng, Heok Hee & Freyhof, Jörg, 2008

Ng, Heok Hee & Freyhof, Jörg, 2008, Two new species of Glyptothorax (Teleostei: Sisoridae) from central Vietnam, Zootaxa 1873, pp. 11-25 : 12-16

Glyptothorax filicatus sp. nov.

( Fig. 1 )

Type material. Holotype: ZFMK 34398, 83.3 mm SL; Vietnam: Thua Thien Hue province, stream draining to Se Sap River, 12 km E of A Luoi, 16°20.57'N 107°9.41'E; J. Freyhof, F. Herder & D. Serov, 20 March 2000.

Paratypes: UMMZ 245668 (1), 69.0 mm SL; ZFMK 34399 (1), 91.9 mm SL; data as for holotype.

Diagnosis. Glyptothorax filicatus can be distinguished from all Indochinese congeners in having a diverging pattern of striae running along the edges of the central depression in the thoracic adhesive apparatus (vs. such striae absent). It is further diagnosed by the following unique combination of characters: dorsal-spine length 13.7–15.1% SL, pectoral-fin length 21.5–21.9% SL, length of adipose-fin base 13.3–15.0% SL, depth of caudal peduncle 8.4–8.8% SL, body depth at anus 15.1–16.0% SL, snout length 48.0–52.9% HL, eye diameter 8.9–9.9% HL, anterior nuchal plate strongly demarcated in beige and caudal peduncle with a pale vertical band.

Description. Biometric data as in Table 1 . Head depressed, body subcylindrical. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile flat to anal-fin base, 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, mid-lateral. Vertebrae 17+21=38* (2) or 18+20=38 (1).

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

Barbels in four pairs. Maxillary barbel long 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 mandibularbarbel 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 base of pectoral spine.

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

Dorsal fin above anterior third of body, with I,6 (3) rays; fin margin convex; spine short, straight; with 3 very small dentations on posterior margin in holotype, smooth in paratypes. Adipose fin with anterior margin straight or very slightly concave, posterior margin angular. Caudal fin strongly forked, with lower lobe very slightly longer than upper lobe and i,7,8,i (3) principal rays. Procurrent rays symmetrical, extending only slightly anterior to fin base. Vertical through anal-fin origin ventral to that through adipose-fin origin. Anal fin with straight anterior margin, straight or slightly concave posterior margin; with iv,10 (3) rays. Pelvic-fin origin at vertical through posterior end of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (3) rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,9 (3) rays; posterior fin margin slightly concave; anterior spine margin smooth, its posterior margin with 9–11 serrae.

Thoracic adhesive apparatus present, consisting of ridges of skin (striae) in ovoid field extending from isthmus to just posterior to level of last pectoral-fin base, with median depression on posterior half. Median striae orientated anteromedially, lateral ones anterodistally to form frond-like pattern ( Fig. 2 a). Striae uninterrupted except for posteriormost lateral ones, which are dissociated into irregular small, unculiferous patches.

ZFMK 34398 ZFMK 34399 UMMZ 245668 Holotype Paratype Paratype Inner mandibular barbel length 33.1 29.5 28.7 Outer mandibular barbel length 49.6 44.5 56.9

Coloration. In 70% ethanol: Dorsal and lateral surfaces of head, and body brownish gray, fading to beige on ventral surfaces. Dorsal and lateral surfaces of body with darker spots randomly and sparsely distributed. Anterior nuchal plate element clearly demarcated in beige. A diffuse, darker brown saddle-shaped blotch on lateral surfaces of body at adipose-fin base, a diffuse darker brown bar running through caudal fin base; these two markings combine to give appearance of a paler vertical band around caudal peduncle. Dorsal fin with brown base and subdistal brown band (band more diffuse on two posteriormost fin rays), rest of fin yellowish. Pectoral and pelvic fins with brown on bases of fin rays and brown band along middle third. Anal fin with brown base and brown melanophores on fin rays forming an irregular subdistal band; rest of fin hyaline. Adipose fin brown, with scattered darker spots and hyaline distal margin. Caudal fin with scattered brown melanophores, irregular W-shaped brown band along middle of fin and tips of lobes hyaline. Maxillary and nasal barbels brown dorsally, beige ventrally.

Etymology. From the Latin adjective filicatus , meaning adorned with ferns, in reference to the frond-like arrangement of the skin ridges on the thoracic adhesive apparatus of this species.

Distribution. Known from the Se Sap River drainage, itself a tributary of the Mekong River ( Fig. 3 ).

Figures

FIGURE 1. Glyptothorax filicatus, ZFMK 34398, holotype, 83.3 mm SL; Vietnam: Se Sap River drainage.

FIGURE 2. Thoracic adhesive apparatus of Glyptothorax species in central Vietnam: a. G. filicatus, ZFMK 34399, paratype, 91.9 mm SL; b. G. honghensis, ZFMK 35755, 67.0 mm SL; c. G. interspinalus, ZFMK 32907, 70.4 mm SL; d. G. lam pr is, UMMZ 232349, 50.4 mm SL; e. G. lao se n si s, ZFMK 24322, 75.5 mm SL; f. G. strabonis, ZFMK 35286, paratype, 95.5 mm SL; g. G. aff. zanaensis, UMMZ 241788, 70.5 mm SL. Illustrations not to scale.

FIGURE 3. Map showing collecting localities of Glyptothorax filicatus and G. strabonis.

Tables

TABLE 1. Biometric data for Glyptothorax filicatus.

Standard length (mm)	83.3	91.9	69.0
%SL
Predorsal length	39.4	38.6	38.8
Preanal length	70.2	69.9	71.0
Prepelvic length	53.1	52.8	53.8
Prepectoral length	22.6	21.2	22.8
Length of dorsal-fin base	14.4	14.1	13.5
Dorsal-spine length	14.3	13.7	15.1
Length of anal-fin base	14.0	14.8	14.6
Pelvic-fin length	17.4	16.3	18.6
Pectoral-fin length	21.7	21.5	21.9
Pectoral-spine length	15.8	14.6	13.9
Caudal-fin length	24.8	25.4	24.9
Length of adipose-fin base	15.0	13.3	13.6
Dorsal to adipose distance	23.2	27.3	23.5
Post-adipose distance	16.2	16.9	17.2
Length of caudal peduncle	20.4	18.7	17.0
Depth of caudal peduncle	8.4	8.5	8.8
Body depth at anus	15.4	16.0	15.1
Head length	29.1	27.6	29.3
Head width	23.4	22.4	22.6
Head depth	15.8	16.5	14.2
%HL
Snout length	52.9	52.8	48.0
Interorbital distance	26.4	26.8	24.8
Eye diameter	9.9	9.1	8.9
Nasal barbel length	27.7	31.5	29.7
Maxillary barbel length	97.9	105.1	89.1