Pterocryptis subrisa, Ng & Lalronunga, 2018

Ng, Heok Hee & Lalronunga, Samuel, 2018, Pterocryptis subrisa, a new silurid catfish (Teleostei: Siluridae) from northeastern India, Zootaxa 4500 (1), pp. 126-134 : 127-128

Pterocryptis subrisa new species

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Fig. 1

Holotype. ZSI FF 7870, 91.8 mm SL; India: Mizoram, Saiha District, Maisa River in the vicinity of Maisa , 22°17'50"N 92°55'3"E; Lalramliana , 9 December 2011.

Paratypes. ZSI FF 7871 (2), 115.6–167.7 mm SL; India: Mizoram, Saiha District, Palak River in the vicinity of Mipu , 22°11'39"N 92°53'46"E; S Lalronunga & Lalramliana. 15 November 2012 . PUCMF 18010 (1), 159.4 mm SL; India: Mizoram, Saiha District, Tuisi River in the vicinity of Khopai , 22°11'44"N 93°01'28"E; S Lalronunga & Lalramliana, 16 November 2012 . PUCMF 18011 (5), 88.1–114.9 mm SL; data as for holotype . PUCMF 12071 (1), 120.4 mm SL; India: Mizoram, Kawlchaw River in the vicinity of Kawlchaw , 22°23'50"N 92°58'11"E; Lalramliana & S Lalronunga, 15 November 2012 . PUCMF 15042 (2), 134.8–139.9 mm SL; India: Mizoram, Saiha District, Kawlchaw River at 22°23'50"N 92°58'11"E; Lalramliana, 24 November 2015 . PUCMF 16020 (1), 156.1 mm SL; India: Mizoram, Saiha District, Tuisi River in the vicinity of Khopai village , 22°11'44"N 93°01'28"E, Lalramliana, 2 March 2016 .

Diagnosis. Pterocryptis subrisa can be distinguished from all congeners except P. barakensis , P. berdmorei , P. gangelica and P. indica in having fewer dorsal-fin rays (2 vs. 4–5). It differs from P. barakensis , P. berdmorei and P. gangelica in having a deeper head (10.6–11.9% SL vs. 8.3–10.8), from P. barakensis and P. gangelica in having a longer supralabial fold (extending posteriorly beyond vertical through posterior orbital margin vs. not or just reaching vertical through posterior orbital margin; Fig. 2 ), and from P. indica in having fewer anal-fin rays (66–75 vs. 85). It is additionally diagnosed from congeners in having the following unique combination of characters: nearly circular eye; head length 17.6–19.6% SL; dorsal-fin height 2.6–4.7% SL; pectoral-fin length 11.8–14.0% SL; body depth at anus 14.4–16.7% SL; caudal peduncle depth 6.8–8.5% SL; confluent anal and caudal fins separated by deep notch; 17 principal caudal-fin rays; and 57 vertebrae.

Description. Morphometric data is given in Table 1. Body subcylindrical in preanal region, laterally compressed posteriorly. Head moderately depressed. Dorsal profile straight, descending gently from dorsal-fin origin to snout tip. Anterior profile of snout rounded. Anterior pair of nostrils tubular and anteromedial to maxillary barbel base. Posterior pair of nostrils bordered by fleshy dorsal and ventral membranes and situated posteromedial to maxillary barbel base. Eyes small, subcutaneous; located in anterior half of head; visible dorsally, but not ventrally.

Mouth subterminal; gape horizontal. Well-developed rictal fold present, consisting of large and fleshy upper lobe joined at corner of mouth with lower lobe; lower lobe subtended by short submandibular groove. Poorlydeveloped supralabial fold present, extending from posterodorsal corner of upper rictal lobe to immediately posterior to vertical through posterior orbital margin.

Teeth villiform. Dentary teeth in slightly curved, elongate bands narrowing posteriorly, reaching from symphysis almost to mouth corners; premaxillary teeth in broader, slightly curved rectangular bands; vomerine teeth in a single crescent-shaped band.

Maxillary barbels slightly flattened, reaching to anterior third of anal fin. One pair of mandibular barbels present; located slightly anterolateral to gular fold; barbels flattened for most of length, reaching to middle of pectoral-fin base.

Gill membranes separate and overlapping, free from isthmus. Branchiostegal rays 11* (4) or 12 (5). Gill rakers short, anteriormost rakers on lower first arch small and widely spaced; 2+3 (1), 2+4* (3), 2+5 (2), 2+6 (1) or 3+5 (2).

Distal margin of dorsal fin pointed, with i, 1 (8) rays; segments of first ray not co-ossified to form spine. Distal margin of pectoral fin broadly convex, with 12* (7), 13 (1) or 14 (1) rays. Segments of the proximal two-thirds of first pectoral-fin element co-ossified, forming spine. Pectoral spine and articulated segments sexually dimorphic in mature individuals. Spine in males with broad and somewhat flattened dorsoventrally, with 0–8 serrations on posterior edge, increasing in size distally; proximal articulated segments with 0–1 serrations on posterior edge. Spine in females or juveniles slender, without serrations on posterior edges of spine proper and proximal articulated segments. Distal margin of pelvic fin convex, with i,7,i (9) rays. Distal margin of anal fin straight, with 66 (1), 68* (3), 69 (1), 72 (1), 73 (1) 74 (1) or 75 (1) rays; joined to caudal fin for length of last anal-fin ray. Integument over anal fin thickened proximally for slightly more than half of ray lengths; fin-ray erector muscles extending along anterior edges of anal-fin rays, ventral most extent of muscles that of thickened integument. Caudal fin emarginate; principal rays i,7,8,i (9).

Urogenital papillae of both sexes located immediately posterior to anus. Males with a conical papilla; females with a similar shaped, but smaller, slightly broader papilla.

Vertebrae 15 + 42 = 57* (5) or 16 + 41 = 57 (1).

Coloration. In 70% ethanol: Dorsal surface and sides of head uniformly brown flanks and thickened integument over anal fin pale brown, with faint mottled pattern. Ventral surfaces of head, breast and belly yellow with scattered melanophores; melanophores less dense ventral to level of eye. Maxillary and mandibular barbels brown, fading to yellow distally. Anal fin with hyaline ventral margin. Caudal, pectoral and pelvic fins with dusky fin rays and hyaline fin membrane. Color in life similar, with a more yellowish tinge overall.

Distribution. This species is known from the Kaladan River drainage in southern Mizoram ( Fig. 3 ).

Habitat. Pterocryptis subrisa has been collected from moderately flowing streams with vegetation on the bank, and a substrate of pebble, sand, gravel and small boulders. The water temperature ranging from 20 to 25 °C and the species is found syntopically with Garra spp. Badis sp. and Devario aequipinnatus .

Etymology. The specific epithet is the perfect passive participle of the Latin verb subrideo, meaning to smile. The name is used in allusion to the longer supralabial fold in this species, which vaguely resembles a smiling countenance.

Figures

FIGURE 1. Pterocryptis subrisa, holotype, ZSI FF 7870, 91.8 mm SL; India: Maisa River.

FIGURE 2. Lateral views of heads of: a. P.subrisa, PUCMF 18011, paratype, 93.6 mm SL; b. P. gangelica, ZRC 60007, 92.8 mm SL showing posterior extent of supralabial fold (indicated with black arrows) in relation to the posterior orbital margin (indicated with white dashed line). Images not to scale.

FIGURE 3. Map showing collection localities of Pterocryptis subrisa. Open symbol represents type locality.