Glyptothorax stibaros, Ng, Heok Hee & Kottelat, Maurice, 2016

Ng, Heok Hee & Kottelat, Maurice, 2016, The Glyptothorax of Sundaland: a revisionary study (Teleostei: Sisoridae), Zootaxa 4188 (1), pp. 1-92 : 81-86

Glyptothorax stibaros new species

( Fig. 39 )

Glyptothorax major (non Boulenger, 1894)— Imaki et al., 1981: 41, Fig. 85; Roberts, 1989: 134, Fig. 104 upper (in part); Kottelat et al., 1993: pl. 37.

Glyptothorax nieuwenhuisi (non Vaillant, 1902)— Jiang et al., 2011: 280.

Glyptothorax fuscus (non Fowler, 1934)— Rainboth et al., 2012: Pl. 38, Fig. 842.

Type material. Holotype: MZB 17215, 55.3 mm SL; Borneo: Kalimantan Barat, Sanggau, km 249 to Pontianak on Sosok–Sanggau road, 0°9'38"N 110°29'28"E; H. H. Tan et al., 26 April 1998.

Paratypes: ZRC 39494 (2), 41.0– 47.7 mm SL; Sarawak: Sungai Stok Muda in the vicinity of Lundu , 1°28'51"N 109°58'18"E; H. H. Tan et al., 6 September 1995 . ZRC 49134 (1), 48.9 mm SL; data as for holotype . CAS 49416 (1), 46.5 mm SL; Kalimantan Barat: small forest stream flowing into Kapuas mainstream NE of Gunung Setunggul , 53 km SW of Sintang and 10 km NW of Silat, 0°24'N 111°51'E; T.R. Roberts & S. Wirjoatmodjo, 16 August 1976 . ZRC 53527 (1), 55.4 mm SL; Kalimantan Barat: Sungai Sawak at km 377 to Pontianak along Sintang–Pontianak road, near turnoff to Nanga Pinoh , Kapuas River drainage, 0°1'25"S 112°27'0"E; H. H. Tan et al., 15 August 2007 . ZRC 49135 (2), 39.4–42.1 mm SL; Kalimantan Barat: Sintang, km 463 to Pontianak on Nangapinoh–Nangasayan road, 0°29'55"S 111°48'7"E; H. H. Tan et al., 24 April 1998 . CMK 11756 (1), 47.8 mm SL; Kalimantan Barat: Sungai Pala at Pala Hulu (Kec. Siberuang, Kp. Renyai Hulu), km 101 on road from Sintang to Putussibau , 0°21'42"N 111°55'47"E; M. Kottelat, 16 June 1995.

Diagnosis. Glyptothorax stibaros is distinguished from Sundaic congeners except G. decussatus in having 5–7 small serrations (vs. smooth or with up to 6 low projections) on the posterior margin of the dorsal-fin spine. It differs from G. decussatus in lacking (vs. having) anteromedial striae in the thoracic adhesive apparatus; a more tapering body, as manifested by the larger ratio between the body and caudal peduncle depths (caudal peduncle depth 3.4–3.8 times in body depth at dorsal-fin origin vs. 2.0); and a more slender caudal peduncle (depth 6.9–8.2% SL vs. 10.3–10.9). Glyptothorax stibaros is futher distinguished from Sundaic congeners in having the following unique combination of characters: premaxillary tooth band approximately one-third exposed when mouth is closed; eye diameter 7–9% HL; head width 19.2–22.4% SL; anteromedial striae in thoracic adhesive apparatus absent; pectoral-fin spine length 18.1–22.2% SL; predorsal length 39.1–42.8% SL; dorsal-fin spine length 15.9–20.4% SL; pectoral-fin spine length 18.1–22.2% SL; large tubercles on abdominal region; dorsal-to-adipose distance 15.1– 21.3% SL; adipose-fin base length 14.6–17.8% SL; straight dorsoposterior margin of adipose fin; prepelvic length 48.8–55.3% SL; body depth at anus 15.6–20.6% SL; caudal peduncle length 16.0–19.7% SL; caudal peduncle depth 3.4–3.8 times in body depth at dorsal-fin origin; post-adipose distance 15.7–18.3% SL; and a slightly mottled body lacking both dark vertical bars and prominent pale midlateral stripe.

Description. Morphometric data in Table 17 . Head depressed; body robust, subcylindrical. Dorsal profile rising steeply and 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 straight 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 tubercles of even size on sides of body. Lateral line complete and midlateral. Vertebrae 16+18=34* (4) or 17+18=35 (1).

Head depressed and broad, triangular when viewed laterally. Snout prominent. Anterior and posterior nares large and separated only by base of nasal barbel. Gill opening broad, extending from ventral margin of posttemporal to isthmus. First branchial arch with 2+6 (1), 2+7 (10) or 3+8* (1) rakers. 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 midway between its base and anterior orbital margin. Inner mandibular-barbel extending to midway between its base and that of pectoral spine. Outer mandibular barbel extending to two-thirds of distance between its base and that of pectoral spine.

Mouth inferior, premaxillary tooth band partially (approximately one-third) exposed when mouth is closed. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary teeth appearing in single broad semilunate band. Dentary teeth in a single crescentic band, consisting of two separate halves tightly bound at midline.

Thoracic adhesive apparatus consisting of keratinized striae in an ovate field extending from isthmus to just beyond posterior limit of pectoral-fin base ( Fig. 3 q). Anteromedial striae absent. Chevron-shaped medial pit on posterior third.

Dorsal fin located above anterior third of body, with I,6 (6) rays; fin margin straight or slightly concave; spine short and straight, smooth on anterior margin and with 5–7 small serrations (holotype =7) on posterior margin. Adipose fin with anterior margin straight or slightly concave and posterior margin straight. Caudal fin strongly forked, with lower lobe slightly longer than upper lobe and i,7,8,i (6) principal rays. Procurrent rays symmetrical and extending only slightly anterior to fin base. Anal-fin base vertically opposite adipose-fin base. Anal fin with straight anterior margin and straight or slightly concave posterior margin; with iv,8,i* (3) or iv,9,i (3) rays. Pelvicfin origin at vertical through posterior limit of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (6) rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,7 (i) or I,7,i* (5) rays; posterior fin margin slightly concave; anterior spine margin smooth, posterior margin with 6–12 (holotype =12) serrations.

Coloration. In 70% ethanol: dorsal and lateral surfaces of head and body reddish to medium brown, fading to paler color (beige to light gray) on ventral surfaces. Dorsal and lateral surfaces of head and body with small irregular darker spots in some individuals. A thin, cream mid-dorsal stripe extending from base of last dorsal-fin ray to origin of adipose fin; stripe indistinct or nearly absent in some individuals. Laterosensory pores rimmed in beige, imparting appearance of a diffuse light brown midlateral line in some individuals. Dorsal and ventral surfaces of caudal peduncle slightly paler in some individuals. All fins with fin rays proximally brown or gray, becoming hyaline more distally, and diffuse melanophores on fin membranes. Pectoral and pelvic fins with brown or gray on base of fin rays and hyaline posterior margin. Anal fin with brown base; brown spot on anterior third of fin present in some individuals. Adipose fin brown with hyaline distal margin. Base of caudal fin with dark crescent in most individuals. Each caudal-fin lobe with irregular, elongate brown or gray blotch on about half of outer fin rays; most of inner rays of lobes hyaline. Maxillary and nasal barbels brown to gray dorsally, beige ventrally. Mandibular barbels beige.

Habitat. Glyptothorax stibaros inhabits small, forested streams with a moderate current and a substrate of sand and gravel; leaf litter and logs are usually present in the streambed.

Distribution. Glyptothorax stibaros is known from river drainages in western and northwestern Borneo, from the Kapuas River drainage northwards to the Sungai Stamin drainage ( Fig. 35 ).

Etymology. The specific epithet comes from the Greek adjective στιβαρός, meaning stout or sturdy, in reference to the relatively deep body (when compared to the caudal peduncle depth) of this species.

Comparisons. Besides G. decussatus (already compared to G. stibaros in the diagnosis), there are four other congeners known from Borneo: G. exodon , G. major , G. nieuwenhuisi , and G. pictus . Glyptothorax stibaros further differs from G. exodon in having the premaxillary teeth one-third (vs. almost entirely) exposed when the mouth is closed, a smaller eye (diameter 7–9% HL vs. 10–13), a shorter dorsal-to-adipose distance (15.1–21.3% SL vs.

21.9–26.3), and a less contrasting color pattern on the body (compare Figs. 7 and 37 ), from G. major in lacking (vs. having) anteromedial striae in the thoracic adhesive apparatus and having a more tapering body, as manifested by the larger ratio between the body and caudal peduncle depths (caudal peduncle depth 3.4–3.8 times in body depth at dorsal-fin origin vs. 1.7–2.4). It is distinguished from G. nieuwenhuisi in having a more tapering body, as manifested by the larger ratio between the body and caudal peduncle depths (caudal peduncle depth 3.4–3.8 times in body depth at dorsal-fin origin vs. 2.1–2.4), and from G. p i ct u s in having a more slender caudal peduncle (depth 6.9–8.2% SL vs. 8.4–10.9) and lacking (vs. having) dark vertical bars at the adipose-fin base and the base of the caudal fin.

Among the remaining Sundaic congeners, G. stibaros is further distinguished from G. amnestus in lacking (vs. having) anteromedial striae in the thoracic adhesive apparatus and a more slender caudal peduncle (depth 6.9–8.2% SL vs. 9.8–11.2), from G. famelicus in having a greater predorsal length (39.1–42.8% SL vs. 32.1–35.2), longer dorsal- (15.9–20.4% SL vs. 8.9–14.0) and pectoral-fin spines (18.1–22.2% SL vs. 14.0–15.6), a longer adipose-fin base (14.6–17.8% SL vs. 11.4–12.8), a deeper body (depth at anus 15.6–20.6% SL vs. 11.4–14.3), a shorter postadipose distance (15.7–18.3% SL vs. 19.1–22.0), and lacking (vs. having) a prominent pale midlateral stripe on the body, and from G. f u s cu s in having larger tubercles on the abdominal region ( Fig. 15 ) and a more tapering body, as manifested by the larger ratio between the body and caudal peduncle depths (caudal peduncle depth 3.4–3.8 times in body depth at dorsal-fin origin vs. 2.3–2.8). It further differs from G. k el u k in having a straight (vs. convex) dorsoposterior margin of the adipose fin and a deeper body (depth at anus 15.6–20.6% SL vs. 14.0–15.8), from G. ketambe in having a wider head (19.2–22.4% SL vs. 16.1–17.9), greater predorsal (39.1–42.8% SL vs. 33.3–35.9) and prepelvic (48.8–55.3% SL vs. 45.4–47.8) lengths, longer dorsal- (15.9–20.4% SL vs. 12.5–14.8) and pectoralfin spines (18.1–22.2% SL vs. 14.3–16.6), a deeper body (depth at anus 15.6–20.6% SL vs. 12.7–15.3), a shorter post-adipose distance (15.7–18.3% SL vs. 19.5–21.7), a shorter caudal peduncle (length 16.0–19.7% SL vs. 20.1– 22.9), and lacking (vs. having) a prominent pale midlateral stripe on the body, and from G. platypogon in having a longer pectoral-fin spine (18.1–22.2% SL vs. 13.6–17.9), a straight (vs. convex) dorsoposterior margin of the adipose fin, a more slender caudal peduncle (depth 6.9–8.2% SL vs. 8.0–11.4) and a longer caudal fin (26.4–32.3% SL vs. 20.1–27.0). Glyptothorax stibaros can be further distinguished from G. plectilis in lacking (vs. having) anteromedial striae in the thoracic adhesive apparatus and a more slender caudal peduncle (depth 6.9–8.2% SL vs. 8.4–10.6), and from G. prashadi in having a more tapering body, as manifested by the larger ratio between the body and caudal peduncle depths (caudal peduncle depth 3.4–3.8 times in body depth at dorsal-fin origin vs. 1.8–1.9) and a shorter, more slender caudal peduncle (length 16.0–19.7% SL vs. 20.1–22.2; depth 6.9–8.2% SL vs. 8.3– 10.3). It further differs from G. robustus in having (vs. lacking) a medial pit in the thoracic adhesive apparatus, a longer predorsal distance (39.1–42.8% SL vs. 36.7–40.0) and lacking (vs. having) a prominent dark longitudinal band running through each caudal-fin lobe, and from G. s c h m i d t i in having a longer predorsal distance (39.1– 42.8% SL vs. 31.6–36.9), a longer dorsal-fin spine (15.9–20.4% SL vs. 8.9–14.9), a longer pectoral-fin spine (18.1–22.2% SL vs. 14.0–18.3), a longer adipose-fin base (14.6–17.8% SL vs. 10.1–14.9), a shorter dorsal-toadipose distance (15.1–21.3% SL vs. 23.9–28.1), a shorter post-adipose distance (15.7–18.3% SL vs. 18.9–22.0), a deeper body (depth at anus 15.6–20.6% SL vs. 11.4–15.7) and lacking (vs. having) a prominent pale midlateral stripe on the body.

Figures

FIGURE 3. Thoracic adhesive apparatus of: a. Glyptothorax amnestus, ZRC 54231, paratype, 51.2 mm SL; b. G. decussatus, MZB 17216, holotype, 74.5 mm SL; c. G. exodon, BMNH 1982.3. 29.190, paratype, 63.2 mm SL; d. G. famelicus, USNM 193015, holotype, 73.3 mm SL; e. G. f u s c u s, ZRC 42123, 54.3 mm SL; f. G. keluk, MZB 17217, holotype, 52.5 mm SL; g. G. ketambe, MZB 8694, holotype, 100.0 mm SL; h. G. major, ZRC 38761, 59.1 mm SL; i. G. nieuwenhuisi, MZB 16475, 61.0 mm SL; j. G. pictus, MZB 17218, holotype, 54.2 mm SL; k. G. platypogon, ZRC 48376, 56.3 mm SL; l. G. platypogonides, UF 166626, 52.4 mm SL; m. G. plectilis, ZRC 46420, paratype, 44.3 mm SL; n. G. prashadi, CMK 25369, 50.7 mm SL; o. G. robustus, ZRC 48377, 59.9 mm SL; p. G. schmidti, CMK 4536, 74.6 mm SL; q. G. stibaros, MZB 17215, holotype, 55.3 mm SL. Illustrations not to scale.

FIGURE 7. Lateral views of caudal region of: a. Glyptothorax amnestus, ZRC 38708, 54.1 mm SL; b. G. keluk, MZB 17217, holotype, 52.5 mm SL. Illustrations not to scale.

FIGURE 15. Left abdominal region showing differences in tubercle size of: a. Glyptothorax fuscus, ZRC 38732, 55.7 mm SL; b. G. stibaros, MZB 17215, holotype, 55.3 mm SL. Illustrations not to scale.

FIGURE 35. Thoracic adhesive apparatus of Glyptothorax prashadi: a. CMK 25369, 50.7 mm SL; Myanmar: Tenasserim River drainage; b. CMK 22046, 53.8 mm SL; Thailand: Kapoe River drainage, showing differences in morphology of striae posteriorly. Striae broken up into round plaques indicated with arrow. Illustrations not to scale.

FIGURE 37. Glyptothorax robustus, ZRC 48377, 59.9 mm SL; Java: Jawa Barat, Cisadane River. Dorsal, lateral and ventral views.

FIGURE 39. Glyptothorax stibaros, MZB 17215, holotype, 55.3 mm SL; Borneo: Kalimantan Barat, Sanggau. Dorsal, lateral and ventral views.

Tables

TABLE 17. Morphometric data for Glyptothorax stibaros (n = 6).

	Holotype MZB 17215	Range	Mean±SD
Standard length (mm) %SL	55.3	41.0–55.4
Predorsal length Preanal length Prepelvic length	39.1 66.4 55.3	39.1–42.8 62.8–66.4 48.8–55.3	40.7±1.05 64.6±1.42 51.8±2.04
Prepectoral length Length of dorsal-fin base Dorsal-fin spine length	19.9 14.3 18.6	19.2–22.9 13.2–15.7 15.9–20.4	21.5±1.37 14.3±0.82 18.6±1.35
Length of anal-fin base Pelvic-fin length Pectoral-fin length	17.4 14.1 24.2	15.1–17.4 13.4–16.1 21.3–26.8	16.4±0.72 14.4±0.91 23.9±1.65
Pectoral-fin spine length Caudal-fin length Length of adipose-fin base	20.3 31.5 17.2	18.1–22.2 26.4–32.3 14.6–17.8	19.7±1.29 29.8±1.80 16.4±1.16
Dorsal to adipose distance Post-adipose distance Length of caudal peduncle	18.4 18.3 17.5	15.1–21.3 15.7–18.3 16.0–19.7	18.9±1.95 17.2±1.13 17.6±1.33
Depth of caudal peduncle Body depth at anus Body depth at dorsal-fin origin	7.4 20.6 25.9	6.9–8.2 15.6–20.6 23.7–25.9	7.5±0.44 17.9±1.97 25.0±1.13
Head length Head width Head depth	26.8 21.7 16.5	26.8–28.7 19.2–22.4 15.9–18.0	27.8±0.79 21.4±0.96 17.0±0.62
%HL Snout length Interorbital distance	50 31	44–50 26–31	48±2.0 29±1.9
Eye diameter Nasal barbel length Maxillary barbel length	8 26 101	7–9 15–30 81–101	8±0.7 21±5.6 91±7.5
Inner mandibular barbel length Outer mandibular barbel length	55 67	31–55 44–67	42.±7.0 56±7.0