Nemacheilus tebo, Hadiaty & Kottelat, 2009

Hadiaty, Renny Kurnia & Kottelat, Maurice, 2009, Nemacheilus Tebo, A New Loach From Sangkulirang Karst, East Kalimantan, Indonesia (Teleostei: Nemacheilidae), Raffles Bulletin of Zoology 57 (1), pp. 119-125 : 120-123

Nemacheilus tebo , new species

( Fig. 3 )

Holotype. – MZB 13367, 56.1 mm SL (70.8 mm TL); Indonesia: Kalimantan Timur: Berau Regency, Kelai District, Merapun Village , Lake Tebo area , a pond at mouth of west cave, site 2 (17°00'13"N 54°10'54"E); coll. R. Hadiaty, Sokir & Cai, 31 Aug.2004.

Paratypes. – All from Indonesia: Kalimantan Timur: Berau Regency, Kelai District , Merapun Village , Lake Tebo area . BMNH 2007.11.30.1, 1, 43.8 mm SL (58.4 mm TL); CMK 18909, 3, 35.9–45.0 mm SL (46.3–56.2 mm TL); MZB 13380, 2 , 37.5–41.1 mm SL (48.8–52.5 mm TL); UF 165707, 1 , 38.6 mm SL (49.8 mm TL); USNM 388744, 2 , 40.4 – 40.4 mm SL (52.6–53.8 mm TL); ANSP 187006, 1 , 42 mm SL (55.1 mm TL); same data as holotype. - MZB 13359, 3 , 36.1–40.7 mm SL (47.7–52.2 mm TL); cave behind camp, site 3 (16°56'08"N 54°07'35"E); coll. R. Hadiaty, Sokir & Cai, 30 Aug.2004 . - MZB 13360 , 4 , 37.1–44.9 mm SL (48.3–56.4 mm TL); ZRC 50728 , 1 , 40.6 mm SL (51.1 mm TL); entrance of cave northwest of camp, site 1 (17°00'16"N 54°11'59"E); coll. R. Hadiaty, Sokir & Cai, 31 Aug.2004.

Additional material (non types). – MZB 13341, 43 , 18.8–48.2 mm SL (23.6–62.6 mm TL): Tuba-tubaan river , site 6 (16°41'20"N 54°05'02"E); coll . R. Hadiaty, Sokir & Cai, 30 Aug.2004 . - MZB 13346, 2 , 37.5–41.6 mm SL (48.0– 54.2 mm TL); Gua Keluar , site 4 (16°41'01"N 54°04'43"E); coll . R. Hadiaty, Sokir & Cai, 30 Aug.2004 . - MZB 13379, 1 , 31.8 mm SL (42.3 mm TL); Lake Tebo (16º49'54"N 54º07'43"E); coll . R. Hadiaty, 28 Aug.2004 .

Diagnosis. – Nemacheilus tebo belongs to the N. selangoricus group, diagnosed by the presence of longitudinal rows of elongated scales on the caudal peduncle, each scale with a tubercle at posterior extremity ( Fig. 4a ). It is distinguished from all other species of Nemacheilus by its unique colour pattern: flank with 11–16 dark brown bars, those in front of the dorsal fin short, close together or fused, forming a kind of large elongate dark brown blotch; those below and behind the dorsal fin distinct, usually continuous across dorsum, irregularly shaped, usually wider along the dorsal midline and along lateral line, narrower in-between. Nemacheilus tebo is distinguished from the other species of the N. selangoricus group by having smaller tubercles, and by the presence (vs. absence) of rows of tubercles on the lower half of the flank. Further, it is distinguished from N. selangoricus and N. spiniferus in missing the long, acuminate posterior projection on the elongated scales on the caudal peduncle (vs. presence, with the tubercle located at the tip of the projection) and by the absence of the black spot at the base of the anterior dorsal-fin rays and of the rows of black spot on the rays (vs. presence). Morphometric characters distinguishing N. tebo from N. selangoricus and N. tuberigum are mentioned under Discussion.

Description. – See Fig. 3 for general appearance and Table 1 for morphometric and meristic data of holotype and 17 paratypes. An elongate nemacheiline with body depth 11.3–14.8 % SL, slowly increasing from head up to dorsalfin origin. Behind dorsal fin, body depth decreasing slowly to caudal-fin base. Head slightly depressed; body slightly depressed anteriorly to compressed posteriorly. Pectoral fin reaching about halfway to pelvic-fin base. Axillary pelvic lobe present. Pelvic fin reaching about halfway of distance to anal-fin origin, just reaching anus, which is about one eye diameter in front of anal fin. Origin of anal fin slightly in front of vertical through dorsal-fin origin. Caudal fin forked. Low ventral and dorsal adipose crests on posterior half of caudal peduncle, which is 1.3–2.0 times longer than deep. Distal margin of dorsal fin straight. Largest recorded size 56.1 mm SL, 70.8 mm TL.

Dorsal fin with 4 simple and 9–10½ branched rays. Anal fin with 3 simple and 5½ branched rays. Caudal fin with 9+8 branched rays. Pectoral fin with 12 rays; anterior rays often with a row of small tubercle; in a 44.1 mm SL specimen, tubercles on first ray about 30 µm wide and 20 µm high ( Fig. 4c ). Pelvic fin with 8 rays.

Vertebrae counts: 23+12=35 (2), 24+12=36 (1), predorsal vertebrae 11 (2), 12 (1).

Body completely covered by small, deeply embedded scales. On a clear and stained specimen, scales on ventral part of head and belly scattered, not embedded as on dorsum and flank. Three to five rows of enlarged scales on flank, from pectoral-fin base to above pelvic fin base. One row above lateral line, other rows below lateral line, 2–4 rows under pectoral fin, 5–6 rows above pelvic fin base, 2–3 rows before end of pelvic-fin base. Each scale bearing a small tubercle on posterior extremity. On caudal peduncle, 7–10 enlarged scales on one row above and one row below lateral line, each with a tubercle at posterior extremity ( Fig. 4a, b ). Largest specimen (holotype, 56.1 mm SL) with a single tubercle on lateral line scales on caudal peduncle.

Lateral line complete, reaching to caudal-fin base, with 80–85 pored scales. Cephalic lateral line system with 6 supraorbital, 4 + 9–10 infraorbital, 7 preoperculo-mandibular and 3 supratemporal pores.

Anterior nostril at tip of a short pointed tube. Mouth gape about 1.7 times wider than long. Lips thin but fleshy, with about 5 folds on lower lip ( Fig. 5b ). A median incision in upper lip. A median interruption in lower lip. Processus dentiformis present. A median notch in lower jaw. Inner rostral barbel reaching to vertical of middle of eye; outer one reaching slightly behind preopercle. Maxillary barbel reaching to middle of opercle.

Colour pattern. – In life: body background beige, with 11–16 dark olive green bars on fl ank. Bars in front of dorsal fin short, not very distinct, close together or fused, forming a kind of large elongate blotch under pectoral fin. Below and behind dorsal fin, bars distinct, usually continuous across dorsum, irregularly shaped, usually wider along dorsal midline and along lateral line, narrower in-between, and vertical median area slightly paler than margins. Ventral part of body creamy. A conspicuous elliptical black blotch on lower half of caudal-fin base, not reaching ventral midline. A narrow dark olive green bar below middle of eye. Preserved specimens: dark brown bars and dorsum, whitish on belly and between bars.

Fin membranes hyaline, rays dusky. Dorsal fin with a short faint mark on lower third of last simple ray.

Sexual dimorphism. – Male with suborbital flap ( Fig. 5a ) and much more tubercles on flank (from pectoral-fin base to above pelvic fin base) than female. In the largest specimen (holotype) the flap is reduced in size.

Distribution and habitat. – Nemacheilus tebo is currently known only from Lake Tebo drainage, Kalimantan Timur, Indonesia. Lake Tebo area was densely covered by big trees, which made the area very green and lush, but the area was burnt in 1997’s Borneo fires. The expedition was conducted during the dry season and the area was very dry. The water level of Lake Tebo was low (depth unknown, reported by locals to be “more than 5 meters”; Fig. 6a ) and we could find only few water bodies inhabited by fishes, usually in front of the entrance of caves. These apparently are the normal dry season conditions, especially after burning. In the rainy season, the water level increases and covers all of the valley area.

All the specimens of N. tebo collected in Tuba-tubaan stream were very emaciated. The stream had very little running water, the depth was only about 10–20 cm and the width about 1–2 m ( Fig. 6b ). The fishes were usually observed in small groups of about 1–20 individuals in shallow water, but in deeper spots several thousands of fish trapped by the low waters formed large dark masses. In both Tuba-tubaan and Lake Tebo we observed many fish dying. In Lake Tebo, the fishes were very crowded in the drying water bodies, and small fish dying were also observed there. Some of them were not able to swim, and were preyed upon by swarming insects (water beetles, Dysticidae).

The Tuba-tubaan is named so because some of local peoples (who harvest edible birds’ nest inside the caves surrounding the lake) used tuba ( Derris sp. , Fabaceae ), a plant from which is extracted rotenone, an effective ichthyocide. The stream and the lake are the only water sources available for most of the local vertebrates.

Etymology – Named after the Lake Tebo. A noun in apposition.

Figures

Fig. 3. Nemacheilus tebo, MZB 13367, holotype, 56.1 mm SL; Indonesia: Kalimantan Timur: Lake Tebo area, site 2.

Fig. 4. Nemacheilus tebo: a–b. scanning electron micrographs of caudal peduncle of 34.3 mm SL specimen: a, showing elongated scales above and below lateral line; b, close-up view of tubercle; c, scanning electron micrograph of tubercle on first pectoral-fin ray of 44.1 mm SL specimen. Scale bars = 10 µm

Fig. 5. Nemacheilus tebo: a, CMK 18909, paratype, male, 45.0 mm SL; head showing suborbital flap; b, MZB 13367, holotype, 56.1 mm SL; mouth, ventral view.

Fig. 6. a. Lake Tebo; b. Tuba-tubaan river, a small stream flowing out of Gua Keluar (‘Exit Cave’) and entering Gua Masuk (‘Entrance Cave’; on picture).