Labeo lankae Deraniyagala, 1952

Sudasinghe, Hiranya, Ranasinghe, R. H. Tharindu, Goonatilake, Sampath Alwis & Meegaskumbura, Madhava, 2018, A review of the genus Labeo (Teleostei: Cyprinidae) in Sri Lanka, Zootaxa 4486 (3), pp. 201-235 : 218-219

Labeo lankae Deraniyagala, 1952

( Figures 10–11 )

Labeo porcellus lankae Deraniyagala, 1930: 7 ; 1952: 41; Munro, 1955: 47; Mendis & Fernando, 1962: 117; Senanayake, 1980: 149 Labeo porcellus (not Heckel, 1844): Day, 1889: 263 (Haly); Duncker, 1912: 261; Pethiyagoda, 1991: 87; Talwar & Jhingran, 1991: 217; Jayaram & Dhas, 2000: 64.

Material examined. FF 624, 185 mm SL, putative holotype, Sri Lanka , North Central province, Malwathu Oya basin, Anuradhapura: Basavakkulam; FF 624, 194 mm SL, same data as putative holotype; NMSL uncatalogued, 2, 177– 181 mm SL, Sri Lanka , Tammannawa: Pannikam Kulamoya at 25/3 Culvert Anuradhapura to Puttalam road; DZ 3749, DZ 3750, DZ 3755, 3, 119– 180 mm SL, Sri Lanka, Malwathu Oya basin: Medawacchiya; UPZM /F/ 0 100, 2, 158– 179 mm SL: Sri Lanka .

Diagnosis. Labeo lankae is distinguished from all the Sri Lankan and peninsular-Indian congeners by the combination of the following characters: a developed rostral fold; maxillary barbels present; rostral barbels rudimentary or absent; dorsal fin with 10–12 branched rays; lateral line with 36–39 scales; scales in transverse series ½8+1+5–6½; circumpeduncular scales 21–24; eye diameter 18.8–25.3 % HL; in life, a hazy black stripe about two scales high originating behind operculum and extending to caudal peduncle; and all fins suffused with red.

Description. For general appearance see Figure 10 ; morphometric data are provided in Table 2. A medium sized Labeo , maximum size 194 mm SL (present material). Caudal peduncle short, its depth 74.1–97.1 % its length. Eyes medium-sized (18.8–25.3% HL), located slightly dorsolaterally, visible in ventral view.

Rostral fold well developed, overlapping upper lip. Tubercles acanthoid with 3–5 apical spines, tuberculation prominent on rhinal, rostral, and infraorbital fields, minute tuberculation on preorbital field ( Figure 11 ). Upper labial fold with minute papillae in 5–6 rows; lower labial fold with prominent lobed papillae in 4–5 rows ( Fig. 11C,F ). Maxillary barbels present, embedded in lip fold, tips externally visible. Rostral barbels rudimentary (n=8) or absent (n=1), if present, located on rostral flap just above and anterior to upper lip fold.

Dorsal fin with two simple and 10 (1), 11 (5), 12 (3) branched rays, first simple ray stiff, about half length of second simple ray, with few tiny conical tubercles scattered randomly on rays. Pectoral fin with one simple and 15 (1), 16 (8) branched rays. Pelvic fin with one simple and seven (1) or eight (8) branched rays. Origin of pelvic fin beneath origin of 4th branched ray of dorsal fin. Anal fin with two simple and five (8) branched rays, first simple ray stiff, less than half length of second simple ray. Caudal fin forked with 9+8 branched rays in upper and lower lobe respectively. Upper caudal-fin lobe shorter than lower in some specimens (n=4).

Lateral line complete with 36 (1), 37 (2), 38 (5), 39 (1) + 1–3 scales. Scales in transverse series ½8+1+5 (1), ½8+1+5½ (5), ½8+1+6 (2) or ½8+1+6½ (1). Predorsal scales 16 (2), 19 (2), 20 (1), 21 (3), or 23 (1). Prepelvic scales 22 (1), 26 (2), 28 (2), 32 (1), or 35 (1). Circumpeduncular scales 21 (1), 22 (1), 23 (6), or 24 (1).

Coloration. In 70% alcohol ( Fig. 10C ): head and body dull greyish brown dorsally, becoming lighter laterally, off-white ventrally. All fins with a tinge of red on rays. Tubercles whitish.

In life ( Fig. 10A,B ): dorsally rosy grey with metallic green on margins of scales becoming lighter laterally. Scales on sides of body beneath dorsal fin with red patches. A hazy black stripe about two scales high originating behind operculum, proceeding to caudal peduncle, giving appearance of a blotch on caudal peduncle (this black stripe disappears when the fish is stressed). All fins suffused with red. Margin of upper and lower lobe of caudal fin black, lighter when stressed. Sclera of eye red. Tubercles white.

Comparative morphometrics. Labeo lankae can be distinguished from L. porcellus by having ½8 scales between the origin of the dorsal fin and the lateral line (vs. ½6–½7: Fig 4B ); 21–24 (vs. 20–21: Fig 4D ) circumpeduncular scales; a dorsal-fin height of 23.3–28.2 (vs. 22.0–23.2% SL); a pelvic-fin length of 19.3–23.4 (vs. 17.9–18.8% SL); an internarial width of 34.2–38.4 (vs. 31.8–32.1% HL); and, when present, shorter rostral barbels: 1.5–7.7 (vs. 8.3–11.2% HL).

Labeo lankae differs from L. heladiva by having a fewer lateral-line scale count (36–39 vs. 44–51: Fig. 4A ); and rows of 4–5 (vs. 2–3) prominent lobed papillae on the lower labial fold. Labeo lankae is distinguishable from L. fisheri by having ½8 (vs. 7–8) scales between the origin of the dorsal fin and the lateral line; 6–7½ (vs. 5–6: Fig. 4C ) scales between the lateral line and the origin of the anal fin; 21–24 (vs. 17–20: Fig. 4D ) circumpeduncular scales and a longer dorsal fin (23.3–28.2 % SL vs. 18.5–23.4).

Labeo lankae differs from the introduced L. rohita in Sri Lanka by having ½8 (vs 6–½6) scales between the origin of the dorsal fin and the lateral line).

Labeo lankae differs from its Indian congeners L. dussumieri , L. boggut , L. fimbriatus , L. kawrus , L. nigrescens , L. boga , L. dyocheilus , L. gonius by having ½8+1+5–6 scales in transverse series (vs. ½8–10+1+ 6–8 in L. dussumieri ; ½10–12+1+8½– 9 in L. boggut ; ½9–10+1+6½–7½ in L. fimbriatus ; ½7+1+4½ in L. kawrus ; ½6– ½7+1+5½ in L. nigrescens ; 7–½7+1+5–5½ in L. boga ; ½7–½8+1+5½–6½ in L. dyocheilus ; and 12–14+1+10½– 13 in L. gonius ). Further L. lankae differs from L. dussumieri , L. boggut , L. fimbriatus , L. calbasu , L. gonius and L. pangusia by having 36–39 lateral line scales (vs. 50–60 in L. dussumieri ; 55–65 in L. boggut ; 42–47 in L. fimbriatus ; 40–44 in L. calbasu ; 40–42 in L. pangusia and 65–80 in L. gonius ). Additionally, L. lankae differs from L. boggut , L. nigrescens , L. boga , and L. gonius by having 21–24 circumpeduncular scales (vs. 26–32 in L. boggut ; 20–21 in L. nigrescens ; 18–21 in L. boga and 25–28 in L. gonius ). Labeo lankae can also be distinguished from L. boggut , L. fimbriatus , L. nigrescens , L. boga , L. calbasu , L. dyocheilus , L. gonius and L. kontius by having 10–12 branched dorsal-fin rays (vs. 9–10 in L. boggut ; 15–19 in L. fimbriatus ; 14 in L. nigrescens ; 8–9 in L. boga ; 12–15 in L. calbasu ; 9–10 in L. dyocheilus ; 14–16 in L. gonius ; and 12–14 in L. kontius ) and it differs from L. potail by the presence (vs. absence) of barbels.

Figures

FIGURE 4. Boxplots representing the distribution of A, lateral-line scales; B, total scales in transverse series; C, scales between lateral line and anal-fin origin; and D, circumpeduncular scales in Labeo lankae (N=9), L. porcellus (N=3), L. fisheri (N=14), L. heladiva (N=42), and L. dussumieri (N=7), based on material examined.

FIGURE 10. Labeo lankae; A, in life in natural habitat (~170 mm SL, not collected); B, in aquarium (~120 mm SL, not collected); C, in preservation (DZ 3750, 180 mm SL); Sri Lanka, Kanadara Oya, Medawacchiya, tributary of Malwathu Oya basin.

FIGURE 11. Detail of head of Labeo lankae in A,D, lateral; B,E; dorsal; and C,F, ventral view. (A–C, DZ 3750, 180 mm SL; D–F, DZ 3755, 171 mm SL).