Parachiloglanis bhutanensis, Thoni, R. J. & Gurung, D. B., 2014

Thoni, R. J. & Gurung, D. B., 2014, Parachiloglanis bhutanensis, a new species of torrent catfish (Siluriformes: Sisoridae) from Bhutan, Zootaxa 3869 (3), pp. 306-312 : 307-311

Parachiloglanis bhutanensis , sp. nov.

Khaling Torrent Catfish ( Fig. 1 )

Holotype. UF 236349, 101.5 mm SL; Bhutan: Trashigang Dzongkhag, Khalingchhu stream, 100 m above bridge. N27 o 11.513 E091 o 36.059. Collected by Ryan Thoni and D.B. Gurung, October 22, 2013.

Paratypes. Collected October 22, 2013. Ryan Thoni and D.B. Gurung. 2, College of Natural Resources ( CNR; Royal University of Bhutan, Lobesa, Bhutan) 13001–13002, 79.7–96.7 mm SL; same data as holotype.

Diagnosis. Parachiloglanis bhutanensis differs from P. hodgarti , its only congener, in the presence of 35–40 large lateral-line pores running the length of the body from the posterior edge of the head to the caudal base (versus lateral-line pores greatly reduced or absent), large fleshy adipose fin 4.2–4.6% SL in height (versus 2.2–4.3% SL), a deep head (47–59% HL versus 36–45% HL), longer inner- and outer-mandibular barbels (11.0–16.5% HL versus 5.2–11.0% HL, and 23.9–31.8% HL versus 14.2–23.6% HL, respectively), truncate (versus indented to lunate) caudal fin, and absence (versus presence) of black and white markings on caudal fin. It differs from all other genera in Glyptosterninae in the absence (versus presence) of a post-labial grove on the lower lip.

Description. Morphometric and meristic data for the species are provided in Table 1 ; Live coloration of the species is presented in Figure 1 . Head blunt; rising at roughly a 45-degree angle from snout to point vertical with eye, where slope begins to rise only gradually to dorsal origin; small cleft in dorsal profile at occiput. Body flat or with slight rise posteriorly from posterior edge of dorsal fin to origin of adipose fin. Adipose fin thick and leathery; at its highest point its depth nearly equals that of the caudal peduncle. Body profile along adipose-fin base gradually sloping ventrally from adipose-fin origin to caudal-fin base. Caudal fin truncate. Ventral profile flat from snout to vent; from vent to posterior edge of anal-fin profile rises at angle equivalent to downward slope of dorsal surface at the same point on the body; from posterior edge of anal fin to caudal-fin base slope is gradually upward or flat.

Head broad, roughly as wide across as long. Mouth inferior and gape width nearly equal to depth of head at eye. Maxillary barbels extending outward from base as much as half of the head length; ventral view of mouth and snout resembling a hammer or bell due to the posterior flap of tissue connecting maxillary barbel to mouth; snout width about one and one third head length. Eyes reduced, nearly subcutaneous; located anterodorsally on head.

Dorsal-fin origin located in first third of body; fin short, similar in height to nasal barbel length, with base narrower than height; fin with i,6 rays. Anal fin located in posterior fourth of body; base slightly less than dorsalfin base in length; fin with i,6 rays. Pectoral fins large, with modified adhesive striations lining thick, spinous first ray; fin length about one fourth of standard length. Pelvic fin also with modified first ray; fin length roughly one sixth standard length. Caudal fin rays 16.

Live coloration. Body brown; somewhat translucent. Posterior to operculum and anterior to origin of adipose fin, body grey with some brownish mixture with grey. Lateral line with 35–40 white pores. Leading fin rays reddish-brown. Venter between pectoral- and pelvic-fin insertions grey. White to dusky from posterior to pelvic fins to vent. Reddish brown from vent to caudal base. Area between lower jaw and pectoral-fin insertion yellow with grey area in between distal edges of inner-mandibular barbels. Head pale yellow; red line extending along the posterior margin of maxillary barbel.

Preserved coloration. Body light brown to grey. Lateral-line pores clearly defined and grey to white in color. Venter black, from transparency of skin providing view of dark intestine. Single dark spot present on posterior edge of operculum and anterior portion of body.

Etymology. The species epithet “ bhutanesnis ” is named in honor of being the first fish species scientifically described from within Bhutan. The common name, Khaling Torrent Catfish, is in reference to the village of Khaling, through which flows the stream where it was discovered.

Distribution. Parachiloglanis bhutanensis is currently known from Khalingchhu stream and an adjacent, unnamed stream in the headwaters of the Dangmechhu River, in the Brahmaputra drainage ( Fig 2 ).

Ecology. Parachiloglanis bhutanensis was discovered in a high-velocity, small order stream 2,211 m above sea level ( Fig. 3 ). Relative to their congener in similar streams, they were found in low numbers, with several hours of effort only rendering three specimens. Like P. hodgarti , they were found adhering to the bottom side of boulders, favoring areas of cascades and white water rather than pools. They were associated with large rocks with deep undercut areas versus rocks with only small refuge from the current. The two streams in which they were found are clear, cold-water environments, sourced from mountain springs, precipitation runoff, and snowmelt, and have little algal growth and frequent high-flow events. This species is adapted to a high-velocity environment with adhesive striations on the leading rays of the paired fins for clinging to rocks and an inferior mouth adapted for scraping algae and invertebrates from the substrate.

Figures

FIGURE 1. Lateral view (a) and ventral view (b) of live specimen of Parachiloglanis bhutanensis, UF 236349, holotype, 101.5 mm SL.

FIGURE 2. Type locality of Parachiloglanis bhutanensis.

FIGURE 3. Type locality of Parachiloglanis bhutanensis, Khalinchhu stream, 1 km east of Khaling Village, Trashigang District, Bhutan. Photo taken October 22, 2013.

Tables

TABLE 1. Morphometric and meristic features for Parachiloglanis bhutanensis (n = 3) and P. hodgarti (n = 21).

	P. bhutanensis Range Mean SD	P. hodgarti Range Mean	SD
Morphometrics Standard length (mm) % SL	79.7–101.5 92.6 11.4	41.5–66.2 53.3	6.7
Predorsal length	28.2–31.8 30.6 2.1	30.5–35.0 32.8	1.1
Dorsal-fin base length Dorsal-fin height	9.1–11.0 9.8 1.1 13.6–15.2 14.3 0.9	7.8–11.7 10.0 12.5–15.6 14.0	1.0 1.2
Dorsal-adipose length	24.8–32.0 29.3 3.9	5.6–24.7 16.5	6.3
Adipose-fin length Adipose-fin height	36.5–37.1 36.8 2.1 4.2–4.6 4.4 0.2	29.4–57.1 39.5 2.2–4.3 3.0	8.1 0.7
Caudal-peduncle depth	6.2–6.6 6.5 0.2	4.7–7.6 6.1	0.7
Caudal-peduncle depth w/ adipose Caudal-peduncle length	7.8–9.7 8.7 1.0 8.2–9.3 8.7 0.5	6.0–7.9 7.1 8.2–12.3 10.4	0.5 1.1
Pre-anal fin length	81.9–85.2 83.8 1.7	80.1–86.5 83.1	1.7
Pre-anal length Head length	80.0–80.7 80.4 0.4 20.8–25.4 22.4 2.6	74.7–81.9 79.1 22.8–26.2 24.6	1.7 0.9
Pre-pectoral length	15.2–18.5 17.4 1.9	15.2–19.9 17.9	1.2
Pectoral fin length Pre-pelvic length	22.9–27.6 25.7 2.5 40.1–40.5 40.3 0.2	26.7–30.9 28.8 36.2–42.6 39.7	1.2 1.7
Pelvic-fin length	15.3–18.6 16.8 1.7	18.6–21.8 19.8	0.8
% HL Nasal-barbel length	34.6–50.0 41.0 8.1	24.8–38.4 31.6	4.8
Eye width	5.8–7.4 6.4 0.8	2.8–5.7 4.4	0.6
Head depth at occiput Head depth at eye	46.6–59.3 52.3 6.4 36.9–51.9 43.8 7.6	36.2–44.9 41.8 25.4–38.5 29.2	2.3 3.2
Maxillary-barbel length	74.4–94.3 85.9 10.3	60.7–86.0 71.1	7.5
Inner-mandibular barbel length Outer-mandibular barbel length	11.0–16.5 13.7 2.8 23.9–31.8 28.0 4.0	5.2–11.0 8.1 14.2–23.6 19.0	1.6 2.4
Head width	80.0–103.5 93.5 12.1	70.4–87.2 79.7	4.5
Meristics Dorsal-fin rays	P. bhutanensis 6	P. hodgarti 5–6
Anal-fin rays	6	6–7
Caudal-fin rays	16	15–17