Homaloptera batek, Hui, Tan Heok, 2009

Hui, Tan Heok, 2009, A new species of hill stream loach (Teleostei: Balitoridae) from Central Kalimantan, with redescriptions of Homaloptera tateregani Popta and Homaloptera stephensoni Hora, Zootaxa 2171, pp. 48-64 : 49-55

Homaloptera batek , new species

( Figs. 1–5 )

Holotype. MZB 10990, 75.4 mm SL; Central Kalimantan: Katingan basin; Mendawai sub-basin; Sungei Baha’e, km 64 logging road at buffer zone of Bukit Raya-Bukit Baka National Park (00°47.593’S 112°19.220’E, 218 m asl); H. H. Tan et al., 12–13 Aug 2007.

Paratypes. MZB 10991, 28 ex., ZRC 51743, 28 ex., 32.3–98.6 mm SL; collection data as for holotype.

Diagnosis. Homaloptera batek differs from its congeners in having the following unique combination of characters: adult body pattern (dorsal and lateral) consisting of rounded dark-brown blotches, larger blotches interspaced with smaller ones, cream body and ventrum; juvenile body pattern consisting only of large, dark brown blotches on the dorsum; dorsal-fin origin just anterior to pelvic-fin origin; eight principal, 11–13 secondary pectoral-fin rays (modally 12); no scales on abdomen; scales on anterior dorsal half of body with an unique keeled pattern consisting of one central keel with one or two secondary keels on each side of central keel, the keels not continuous along the scale but interrupted anteriorly ( Fig. 10 A); and 60–61 scales on the lateral line (modally 61). Maximum size: 98.6 mm SL.

Description. General body shape and appearance as in Figs. 1–5 . For meristic and morphometric data see Table 1 . Head elongate, pointed (head width 15.6–17.8 % SL; head depth 8.2–9.6 % SL). Eye small (eye diameter 10.4–13.6 % HL), positioned nearer to opercle edge than to tip of snout; nostril positioned midway between snout tip and opercle edge. Snout long (snout length 59.4–65.5 % HL). Mouth inferior, with three short, fleshy pairs of barbels, two rostral, one maxillary. A shallow groove just posterior to maxillary barbel (i.e., Silas’ definition of a post-rostral groove). Head dorsally covered with many minute tubercles; area at ventrum of head covered with many minute raised bumps and cream-coloured dashes. Body elongate, laterally compressed, deepest at dorsal-fin origin (body depth at dorsal-fin origin 11.3–13.1 % SL), slimmest at caudal peduncle (caudal peduncle depth 4.7–5.2 % SL). Body covered with scales, except for naked ventral area extending from area between pectoral fins to anus and area anterior to anal-fin origin. Anus situated just anterior to anal-fin origin. In juveniles, each body scale with central keel (largest specimen with only central keeled scales examined at 38.2 mm SL); adults with two additional smaller keels angled to and on either side of central keel (mainly on anterior dorsal-half of body, presence of secondary keels in specimens larger than 44.0 mm SL; see Fig. 10 ), the central keel sometimes with one or two additional longitudinal bumps/keels ( Fig. 10 A). Anterior and posterior margins of dorsal and anal fins concave. Pectoral and pelvic fins with rounded anterior margin, pointed tips with concave edge, followed by a rounded posterior edge. Caudal fin deeply forked; lower caudal lobe about 1.30–1.40 times that of upper one. Vertebrae: 21 + 12, total = 33 (n = 8).

Pigmentation in life. See Fig. 5 for adult coloration. Head light yellowish brown, eye with golden brown iris. Dorsum of head with numerous dark-brown blotches, largest blotch just posterior to head in line with opercular openings, two similar blotches on region between eyes, a large blotch between nostrils and two similar blotches on region just anterior to nostrils. Blotch at snout tip, followed by a series of three similar blotches along side to opercle edge; a series of three blotches just above previous series, one below nostril, one below eye and one behind eye; blotches sometimes fused. Barbels tinged with red. Body dorsally light yellowish brown with seven to nine rounded, dark-brown saddle-shaped median blotches; two or three blotches anterior to dorsal-fin origin, one anterior to and overlapping with dorsal-fin origin, one at dorsal-fin base, one overlapping and posterior to dorsal fin, two or three posterior to dorsal fin. Smaller blotches of various sizes fill up area between median blotches; blotches sometimes fused. Lateral body with similar blotch pattern, but some blotches merging towards lower half of body. Ventrum cream. Dorsal fin light yellowish brown, with three or four broad dark-brown bars, its posterior margin hyaline. Caudal fin light brown, its base darker; two broad dark-brown bars on upper caudal lobe and middle of fin, three on lower lobe; caudal fin posterior margin hyaline. Anal fin hyaline, with a single broad dark-brown bar, its anterior ray with two bars; posterior anal-fin margin hyaline. Pelvic fin light yellowish brown, its anterior edge clear, second and third rays dark brown, with three broad dark-brown bars on rest of fin, its posterior margin hyaline. Pectoral fin with similar pattern, but with up to four broad bars.

See Figs. 2–3 for juvenile colouration. Head dorsally light yellowish brown with two dark-brown blotches, one between nostrils and another just posterior to area between eyes. Side of head evenly distributed with dark-brown pigmentation. Body dorsally dark brown, with up to six median, rounded, saddle-shaped blotches and up to six cream-coloured bars separating these; two blotches anterior to dorsal-fin base, two on dorsal fin base, and two posterior to dorsal fin. Side of body with continuation of dorsal saddle-shaped blotches to dorsal half of body, rest of body with dark, evenly distributed pigmentation. Ventrum cream. Dorsal fin with two diffuse, broad, dark-brown bars and hyaline posterior margin. Caudal fin with black base, two broad black bars on upper lobe and middle, its lower lobe almost totally black. Pelvic fin base black, with a single diffused black bar, its posterior margin hyaline. Pectoral fin with black base and two diffused broad black bars, its posterior margin hyaline.

Colour in ethanol. See Figs. 1–4 . Both adult and juvenile colour pattern in preservative similar to that in life, except for basal body colour being cream.

Remarks. Homaloptera batek can be further differentiated from the holotype of the morphologically similar species, H. tateregani , by the following characters: lower caudal lobe with three bars (vs. two); body scales with central and two secondary keels (vs. one); pectoral and pelvic fins with barred pattern (vs. plain); length of lower caudal lobe 1.30–1.44 times that of upper caudal lobe (vs. 1.24); fewer pelvic fin principal rays (two, vs. three); fewer lateral scales (60–61, vs. 63); a greater number of predorsal scales (17–19, vs. 14); a greater number of transverse scales (7.1.6–7, vs. 5.1.6); a greater number of caudal peduncular scales (3.1.4, vs. 3.1.3); shorter total length (127.5–131.7 % SL, vs. 133.1); longer predorsal length (46.1–49.1 % SL, vs. 45.3); longer preanal length (73.8–76.9 % SL, vs. 72.1); deeper body depth at dorsal-fin origin (11.3–13.1 % SL, vs. 10.4); shorter caudal peduncle length (16.3–18.2 % SL, vs. 19.2); shorter dorsal-fin base length (13.9–17.1 % SL, vs. 18.8); shorter anal-fin base length (7.7–9.2 % SL, vs. 10.1); longer snout length (13.2–14.8 % SL, vs. 12.5; 59.4–65.5 % HL, vs. 57.2); smaller orbit (10.4–13.6 % HL, vs. 14.5).

Homaloptera batek can be differentiated from H. stephensoni by the following characters: mouth inferior, with thick fleshy barbels (vs. mouth sub-inferior, with thin barbels); snout long, narrow, with nostril situated between snout tip and opercle edge (vs. snout relatively long, rounded, with nostril nearer snout tip); presence of postoral groove (vs. absence); anus situated just anterior to anal-fin origin (vs. between pelvic and anal-fin origins); dorsum with up to nine dark-brown blotches (vs. six); pectoral and pelvic fins falcate (vs. rounded); length of lower caudal lobe 1.30–1.44 times that of upper caudal lobe (vs. 1.06–1.10); 60–61 lateral scales (vs. 43–50); caudal peduncle more slender (4.7–5.2 % SL, vs. 5.4–6.2); snout longer (13.2–14.8 % SL, vs. 11.2–12.3); eye smaller (10.4–13.6 % HL, vs. 18.3–22.6); interorbital width greater (31.6–37.5 % HL, vs. 17.6–21.3).

Distribution. Homaloptera batek is known only from the upper Katingan River basin in Central Kalimantan ( Fig. 11 ).

Etymology. From the vernacular ‘batek’, a traditional Indonesian patterned cloth, made by hand painting; in allusion to the unique beautiful body pattern, applied as a substantive in apposition.

Field observations. The type locality, Sungei Baha’e, is one of the foothill streams draining from the Bukit Raya-Bukit Baka National Park, which straddles part of West and Central Kalimantan. The peripheral area had been logged intensively over the past 15 years or more. Access to this isolated area is easier from the Melawi River in West Kalimantan and overland via the logging tracks. Sungei Baha’e ( Fig. 6 ) is located next to a logging track at km 64, and this track extends to more than 95 km (as of August 2007). The substrate of the river is a mix of bedrock, boulders, rocks and gravel, with clear, fast-flowing water of pH 6.4. Homaloptera batek was collected only from the fastest water flow in the riffle zone, usually from under submerged rocks and on the bedrock (observed at night). This fish usually orientates itself head against the water flow and creeps along the rock. Other syntopic fish include: Cyprinidae – Garra borneensis , Paracrossocheilus vittata , Rasbora elegans , Tor tambra ; Balitoridae – Homaloptera orthogoniata , H. stephensoni , Hypergastromyzon cf. humilis , Gastromyzon cf. praestans , G. cf. auronigrus , Nemacheilus spiniferus ; Sisoridae – Glyptothorax sp.; Siluridae – Silurichthys citatus . It shares its habitat with another strange endemic Bornean aquatic amphibian, Barbourula kalimantanensis (Bombinatoridae) , which apparently prefers the slower-flowing areas.

Figures

FIGURE 1. Homaloptera batek. Dorsal, lateral and ventral views, ZRC 51743, 98.6 mm SL.

FIGURE 2. Homaloptera batek. Lateral views showing body-pattern variation with size, ZRC 51743, from top to bottom: 96.4, 87.4, 63.5, 38.2 mm SL (not to scale).

FIGURE 3. Homaloptera batek. Dorsal views showing body-pattern variation with size, ZRC 51743, from top to bottom: 96.4, 87.4, 63.5, 38.2 mm SL (not to scale).

FIGURE 4. Homaloptera batek. Oral views showing variation with size, ZRC 51743, from top to bottom: A, 96.4 mm SL; B, 87.4 mm SL; C, 63.5 mm SL; D, 38.2 mm SL.

FIGURE 5. Homaloptera batek, freshly caught, in push net with other syntopic species (taken at night, 12 August 2007).

FIGURE 6. Type locality, Sungei Baha’e, Katingan basin, Central Kalimantan (13 August 2007).

FIGURE 10. Schematised drawings of anterior dorso-lateral body scales of: A, Homaloptera batek, ZRC 51743, 97.2 mm SL; B, H. tateregani, RMNH 7632, 63.2 mm SL; C, H. stephensoni, ZRC 51742, 68.6 mm SL (scale bar = 1 mm).

FIGURE 11. Map of Borneo showing distribution of Homaloptera batek (circle), H. tateregani (triangle) and H. stephensoni (square – solid: type locality, hollow: other locations).

Tables

TABLE 1. Meristic and morphometric data of Homaloptera batek, H. tateregani and H. stephensoni (values in brackets represent the holotypes).

Catalogue numbers Sample size Standard length (mm)	Homaloptera batek , new species MZB 10990 (holotype) ZRC 51743 (paratypes) 10 74.7–97.2 [74.7]	Homaloptera tateregani RMNH 7632 (holotype) 1 63.4	Homaloptera stephensoni RMNH 7633 (holotype) ZRC 51742 6 46.5–68.6 [46.5]
Meristics (mode) Dorsal fin rays Anal fin rays	2, 8–9 (2, 8) [2, 8] 2, 5 [2, 5]	2, 8 2, 5	2, 7 [2, 6] 1, 5 [1, 5]
Caudal fin rays Pelvic fin rays Pectoral fin rays	9+9 [9+9] 2, 8 [2, 8] 8, 11–13 (8, 12) [8, 12]	10+9 3, 8 8, 12	9+9 [-] 2, 8 [2, 8] 5, 12–13 (5, 12) [5, 12]
Lateral scales Predorsal scales Transverse scales	60–61 (61) [61] 17–19 (17) [17] 7.1.6–7 [7.1.6]	63 14 5.1.6	43–48 [50] 19–21 (19, 20) [18] 6.1.5 [6.1.5]
Caudal peduncle scales Scale rows above lateral % Standard length	4.1.5 [4.1.5] 7 [7]	3.1.3 5	3.1.3 [3.1.3] 6 [5]
Total length Body length Predorsal length	127.5–131.7 [129.1] 79.7–82.3 [79.7] 46.1–49.1 [46.4]	133.1 81.2 45.3	128.2–130.3 [-] 78.5–81.8 [79.6] 48.0–50.8 [50.8]
Preanal length Prepelvic length Head length	73.8–76.9 [76.1] 46.8–49.6 [49.6] 21.5–23.1 [22.3]	72.1 47.0 21.8	74.8–78.1 [78.1] 45.6–47.3 [45.8] 22.2–24.4 [23.2]
Body depth at dorsal fin Body depth at anus Caudal peduncle depth	11.3–13.1 [11.3] 7.8–9.1 [8.4] 4.7–5.2 [5.0]	10.4 8.0 5.0	11.0–14.7 [13.3] 8.5–10.8 [10.8] 5.4–6.2 [6.2]
Caudal peduncle length Dorsal fin base length Anal fin base length	16.3–18.2 [16.3] 13.9–17.1 [13.9] 7.7–9.2 [7.7]	19.2 18.8 10.1	15.5–17.1 [15.5] 13.3–15.1 [15.1] 8.1–8.8 [8.6]
Pelvic fin length Pectoral fin length Head depth	18.5–20.9 [20.4] 23.3–24.6 [24.1] 8.2–9.6 [8.7]	24.9 28.5 9.3	18.4–21.9 [21.9] 22.1–25.4 [29.5] 9.5–10.8 [10.8]
Head width Snout length Orbit diameter	15.6–17.8 [17.3] 13.2–14.8 [13.3] 2.4–3.0 [3.0]	17.0 12.5 3.2	14.7–16.5 [15.3] 10.8–12.3 [10.8] 4.2–5.4 [5.4]
Interorbital width % Head length Head depth	7.2–8.4 [7.4] 36.6–42.9 [39.0]	8.2 42.8	4.1–4.8 [4.7] 40.6–46.1 [46.3]
Head width Snout length Orbit diameter	70.3–77.9 [77.9] 59.4–65.5 [59.9] 10.4–13.6 [13.6]	78.3 57.2 14.5	60.4–73.1 [65.7] 46.3–52.3 [46.3] 18.3–23.1 [23.1]
Interorbital width	31.6–37.5 [33.4]	37.7	17.6–21.3 [20.4]