Pethia melanomaculata ( Deraniyagala, 1956 )

Batuwita, Sudesh, Maduwage, Kalana & Sudasinghe, Hiranya, 2015, Redescription of Pethia melanomaculata (Teleostei: Cyprinidae) from Sri Lanka, Zootaxa 3936 (4), pp. 575-583 : 576-580

Pethia melanomaculata ( Deraniyagala, 1956)

( Figures 1A , 2 , 3 A)

Puntius ticto melanomaculatus Deraniyagala, 1956: 34 ; 1958: 129.

Barbus ticto (not Hamilton, 1822): Day, 1878: 576; Senanayake, 1980: 118.

Puntius ticto (not Hamilton, 1822): Deraniyagala, 1952: 35; Munro, 1955: 46; Pethiyagoda, 1991: 118. Puntius melanomaculatus ( Deraniyagala, 1956) : Meegaskumbura et al., 2008: 148. Pethia melanomaculata ( Deraniyagala, 1956) : Pethiyagoda et al., 2012: 71.

Diagnosis. Pethia melanomaculata is distinguished from all the other congeners in Sri Lanka and the peninsula of India by the combination of the following characters: barbels absent; lateral line incomplete, with 7–10 perforated scales; 20–23 scales in lateral series; 3 unbranched dorsal-fin rays, the last one with 8–11 strong serrae; ½4/1/3½ scales in transverse line on body; ½2/1/2½ scales in transverse line on caudal peduncle; predorsal scales 8–9; body depth 32.4–41.5% SL; head length 26.1–29.2% SL; snout length 25.3–35.6% HL; eye diameter 24.4–31.9% HL; a small black humeral spot on the 3rd or 4th lateral-line scales; a black spot on caudal peduncle, on scales 16–18 of the lateral-line series; no prominent projection at postero-lateral border of premaxilla; superior angle of palatine process of maxilla blunt; dorsal border of anguloarticular curved, with a deep concavity; lateral border of 5th ceratobranchial with a deep notch.

Description. See Fig. 1A for general appearance and Table 1 for morphometric data. Body laterally compressed. Dorsal profile of head gently notched above posterior orbital margin. Predorsal profile convex, rising gradually to dorsal-fin origin. Postdorsal profile sloping down to hypural notch. Ventral profile convex up to pelvic-fin base, then almost flat to anal-fin origin, rising markedly between anal-fin origin and insertion, then approximately level to hypural notch. Caudal peduncle short, its depth 1.0–1.4 times its length.

Head small, laterally compressed. Snout blunt, rounded, subequal to eye diameter. Mouth small, subterminal, angle of gape not reaching vertical from anterior margin of eye. Barbels absent. Eyes large, dorsolaterally oriented, closer to tip of snout than to margin of operculum.

Dorsal-fin with its origin posterior to pelvic-fin origin, approximately equidistant from tip of snout and caudalfin base; its distal margin concave; 3 unbranched and 8 branched rays (18), last one strong with 8 (8), 9 (4), 10 (4) or 11 (1) serrae posteriorly. Pectoral fin with 1 unbranched and 11 (2) or 12 (15) branched rays, its tip reaching pelvic-fin base when adpressed. Pelvic fin with 1 unbranched and 8 (16) branched rays, its distal margin rounded, not reaching anal-fin origin when adpressed. Anal fin with 3 unbranched and 5 (17) branched rays, its distal margin concave. Caudal fin forked, with i,8,8,i (1), i,8,9,i (5), i,9,8,i (4), i,9,9,i (7) principal rays.

Lateral line incomplete, with 7–10 pored scales; 20 (4), 21 (9), 22 (3) or 23 (2) scales in lateral series. Scales in transverse line on body ½4/1/3½ (18), predorsal scales 8 (16) or 9 (1), prepelvic scales 9 (3) or 10 (2), scales in transverse line on caudal peduncle ½2/1/2½ (18).

Precaudal vertebrae 16; caudal vertebrae 14. Supraneurals 4. No prominent projection at postero-lateral border of premaxilla. Superior angle of palatine process of maxilla blunt. Lengths of anterior and superior articular borders of infraorbital 3+4 less than half of its width. Tip of coronoid process of dentary blunt. Dorsal border of anguloarticular curved, with deep concavity. Lateral arm of 5th ceratobranchial narrow, pointed, with a small foramen at its base. Fifth ceratobranchial with a deep notch on its lateral border and 5+3+2 small, conical teeth.

Coloration. In preservative, body overall pale brown. A small black humeral spot above pectoral fin, level with mid eye, confined to 3rd or 4th lateral-line scale. Black spot on caudal peduncle larger than humeral spot, somewhat smaller than eye diameter, originating posterior to anal-fin insertion, on scales 16–18 of lateral series. All fins hyaline, without any distinct marks.

In life, dorsally light golden brown. Sides of body iridescent silver with scattered melanophores on distal margin of anterior mid-body scales. Position of humeral and caudal spots same as in preserved specimens. Ventrally white. Prominent markings on dorsal fin absent. Fins hyaline to light yellow. Breeding males with a reddish body coloration.

Distribution. Pethia melanomaculata is restricted to the northern and eastern dry zone (annual rainfall <1,500 mm) of Sri Lanka where it is widely distributed in tanks and small rivers, primarily within the Mahaweli River basin ( Fig. 1 D). It is the only species of Pethia that occurs in the island’s dry zone.

Figures

FIGURE 3. Position of caudal spot in A, Pethia melanomaculata; B, P. punctata; and C, P. ticto. Scale bar: 1 mm.

FIGURE 1. A, Pethia melanomaculata, colour in life (not preserved); B, copy of iconotype of Cyprinus ticto Hamilton, 1822 (Courtesy Linnean Society of London); C, illustration of Puntius ticto, from Day (1878, pl. 144, fig. 7); D, distribution of Pethia species in Sri Lanka: ● Pethia melanomaculata (location of holotype in red); other known locations (black); {■}, Pethia bandula (purple); P. cumingii (yellow); P. nigrofasciata (green); P. reval (blue).

FIGURE 2. A, left dentary (buccal view; CP, coronoid process; AA, anguloarticular); B, left premaxilla (dorsal view); C, left maxilla (buccal view; PP, palatine process); D, left infraorbitals 3 + 4 (lateral view); E, 5 th ceratobranchial: of Pethia melanomaculata (WHT 11066, 32.8 mm SL), P. punctata (WHT 11078, 34.9 mm SL) and P. ticto (WHT 11054, 37.0 mm SL). Scale bar: 1 mm.

Tables

TABLE 1. Morphometric data for Pethia melanomaculata, holotype, NMSL FF 728 / A; and WHT 7719 and WHT 7748 (n = 13).

	Pethia melanomaculata
	holotype mean (s.d)	range
Standard length (mm)	37.4 33.8 (2.3)	31.0–37.4
In percent of standard length
Total length	– 132 (2.3)	128–136
Predorsal length	45.5 55.0 (3.0)	45.5–57.4
Postdorsal length	50.8 54.5 (2.4)	50.8–58.0
Preanal length	65.5 69.9 (2.0)	65.5–72.6
Prepelvic length	46.8 47.5 (1.6)	44.5–50.3
Body depth	32.4 38.3 (2.3)	32.4–41.5
Head length	28.1 27.8 (0.9)	26.1–29.2
Dorsal-fin base length	15.5 17.1 (0.8)	15.5–18.1
Dorsal-fin height	23.0 25.3 (1.5)	23.0–28.4
Anal-fin base length	10.2 11.8 (1.2)	9.7–14.0
Anal-fin depth	17.1 17.0 (1.0)	15.7–18.9
Pelvic-fin length	18.7 21.6 (1.4)	18.7–23.4
Pectoral-fin length	20.1 20.9 (1.5)	16.8–22.4
Caudal-peduncle length	18.7 19.0 (1.9)	16.3–22.5
Caudal-peduncle depth	13.1 15.3 (0.9)	13.1–17.0
Length of upper caudal-fin lobe	– 32.4 (5.2)	27.2–46.8
Length of lower caudal-fin lobe	– 33.0 (1.9)	29.2–36.7
Length of medial caudal-fin rays	10.4 14.7 (1.8)	10.4–16.5
In percent of head length
Snout length	27.6 29.3 (3.1)	25.3–35.6
Orbital diameter	30.5 29.9 (1.9)	24.4–31.9
Interorbital width	33.3 37.6 (2.0)	33.3–39.6
Internarial width	19.0 18.8 (2.9)	12.8–22.0