Glyptothorax strabonis, 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 : 16-20

Glyptothorax strabonis sp. nov.

( Fig. 4 )

Type material. Holotype: UMMZ 245669, 80.1 mm SL; Vietnam: Quang Binh province, market in Phong Nha; J. Freyhof, F. Herder & D. Serov, 7 April 2000.

Paratypes. ZFMK 35285–35286, (2), 84.0, 95.5 mm SL; data as for holotype.

Diagnosis. Glyptothorax strabonis can be distinguished from all Indochinese congeners in having a smaller eye (6.2–6.5% SL vs. 8.6–12.0). It is further distinguished from congeners in central Vietnam by its thoracic adhesive apparatus, which consists of striae arranged in a broad oval field ( Fig. 2 ) and by the unique combination of the following characters: length of caudal peduncle 20.5–21.2% SL, depth of caudal peduncle 7.5–7.6% SL, body depth at anus 13.7–20.9% SL, head width 17.9-18.8% SL, presence of 14–16 serrae on posterior margin of pectoral spine, and coloration consisting of a dark-brown body with indistinct pale midlateral and mid-dorsal stripes.

Description. Biometric data as in Table 2 . 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 (3).

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 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 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– 4 very small dentations on posterior margin. 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, posterior margin with 14–16 serrae.

Thoracic adhesive apparatus present, consisting of ridges of skin (striae) in elongate oval field extending from isthmus to just posterior to level of last pectoral-fin base. Median depression present on posterior third of adhesive apparatus. Striae orientated anterodistally, radiating from median depression. Striae uninterrupted except for posteriormost lateral ones, which are dissociated into irregular small, unculiferous patches.

Coloration. In 70% ethanol: Dorsal and lateral surfaces of head, and body dark brown, fading to beige on ventral surfaces. Nuchal plate elements beige in some individuals. A thin, beige mid-dorsal stripe extending from base of last dorsal-fin ray to origin of adipose fin present in some individuals. Laterosensory pores along lateral line rimmed in beige, imparting appearance of a diffuse beige mid-lateral line in some individuals. Dorsal and pelvic fins with brown fin rays, diffuse melanophores on fin membranes and hyaline distal margin. Pectoral fin 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 hyaline distal margin. Caudal fin brown, with beige procurrent rays and tips of lobes hyaline. Maxillary and nasal barbels brown dorsally, beige ventrally.

Etymology. From the Latin strabonis , meaning one who squints, in reference to the relatively small eye of this species. A noun.

Distribution. Known from the Giang River (Song Giang) drainage in central Vietnam ( Fig. 3 ).

Figures

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.

FIGURE 4. Glyptothorax strabonis, UMMZ 245669, holotype, 80.1 mm SL; Vietnam: Phong Nha market.

Tables

TABLE 2. Biometric data for Glyptothorax strabonis.

	UMMZ 245669 Holotype	ZFMK 35285 Paratype	ZFMK 35286 Paratype
Standard length (mm)	80.1	84.0	95.5
%SL Predorsal length	34.5	33.3	34.9
Preanal length	65.8	67.6	67.1
Prepelvic length Prepectoral length	47.8 23.1	48.6 20.8	51.4 24.1
Length of dorsal-fin base	14.2	13.2	13.2
Dorsal-spine length Length of anal-fin base	14.7 15.7	14.0 14.9	15.1 15.6
Pelvic-fin length	18.2	17.3	18.8
Pectoral-fin length Pectoral-spine length	22.5 16.6	23.8 15.2	27.7 20.4
Caudal-fin length	26.2	27.4	26.2
Length of adipose-fin base Dorsal to adipose distance	16.2 24.1	15.0 23.8	16.1 20.5
Post-adipose distance	17.2	17.7	19.1
Length of caudal peduncle Depth of caudal peduncle	20.5 7.6	21.2 7.5	20.7 9.2
Body depth at anus	14.2	13.7	20.9
Head length Head width	24.3 17.9	23.8 17.9	26.9 18.8
Head depth	14.2	12.7	17.7
%HL Snout length	47.7	51.5	50.2
Interorbital distance	26.2	26.0	27.2
Eye diameter Nasal barbel length	6.2 26.7	6.5 24.0	6.3 27.6
Maxillary barbel length	97.4	101.5	98.1
Inner mandibular barbel length Outer mandibular barbel length	34.9 53.8	29.0 53.5	33.9 52.1