Psilorhynchus piperatus, Conway, Kevin W. & Britz, Ralf, 2010

Conway, Kevin W. & Britz, Ralf, 2010, Three new species of Psilorhynchus from the Ayeyarwaddy River drainage, Myanmar (Teleostei: Psilorhynchidae), Zootaxa 2616, pp. 31-47 : 39-41

Psilorhynchus piperatus , new species

( Figure 6 )

Holotype. BMNH 2010.4.14.8, 47.7 mm SL; Myanmar: Magwe Division, Man Chaung (Ayeyarwaddy River drainage), 0.5 miles from Zinpyone village, 19° 55' 3" N, 94° 30' 11" E, 21 November 2009, R. Britz et al.

Paratype. BMNH 2010.4.14.9, 1, 42.6 mm SL; same data as holotype.

Diagnosis. A species of Psilorhynchus distinguished from all other species of the genus by its unique caudal-fin pigmentation pattern, consisting of an approximately symmetrical pattern of small black blotches on both upper and lower caudal-fin lobes (vs. caudal fin without pigmentation, with two to three irregular vertical bars across center, or with an irregular pigmentation pattern, most prominent along outer edges of upper and lower lobes). Psilorhynchus piperatus is further distinguished by the combination of the following characters: snout length 53–55% HL; ventral surface between paired fins with a broad rectangular scale-less patch; branched dorsal-fin rays 9; unbranched pectoral-fin rays 5; caudal-fin rays 9+9; lateral-line scales 32– 33; lateral sides of body marked with 6 indistinct round to squarish dark-brown blotches, arranged in a longitudinal row; dorsal saddles deep, extending 3–4 scale rows downwards from the dorsal surface, in contact with the round to squarish dark brown blotches, arranged in a longitudinal row on flank.

Description. General body shape as in Figure 6 . Morphometric and meristic data are listed in Table 2. As described for P. brachyrhynchus with the following differences. Snout long, contributing to 50% of head length. Principal caudal-fin rays 9+9. Pelvic-fin rays ii.7, pectoral-fin rays v.11 (1). Pectoral fin reaching to one scale row anterior to pelvic-fin origin when adpressed. Scales large, 32(1) or 33(1) along lateral line, plus 2 on base of caudal fin. 13 predorsal scales, 9(1) or 10(1) scales between anus and anal-fin origin. Ventral surface with a broad, rectangular scale-less patch between paired fins. Total number of vertebrae 35, comprising 19+16 abdominal and caudal vertebrae.

Coloration. As described for P. brachyrhynchus , but with the following differences. Lateral body scales irregularly pigmented, occluding round to squarish dark brown blotches, arranged in a longitudinal row on flank. Dorsal fin weakly marked with a proximal stripe running along base of rays, a more distal stripe crossing center of fin, formed by small aggregations of melanophores around first branching point of branched rays. Caudal fin densely speckled with small dark clusters of melanophores, equally distributed across both upper and lower lobes, forming an approximately symmetrical pattern ( Fig. 4 F).

Distribution and habitat. Psilorhynchus piperatus is known at present only from the type locality ( Fig. 2 ). At the type locality, the Man Chaung is a swift-flowing river ( Fig. 7 ), with dense riparian vegetation and a substrate of sand, gravel and small boulders.

Etymology. From the Latin piperatus , meaning peppered, in allusion to the speckling on the caudal fin. An adjective.

Remarks. Psilorhynchus piperatus is easily distinguished from all other members of the genus by its unique caudal-fin pigmentation pattern ( Fig. 4 F), which consists of a dense speckling of small black spots, formed by clusters of melanophores, distributed evenly over both upper and lower caudal-fin lobes.

TABLE 2. Selected morphometric and meristic date for Psilorhynchus piperatus .

Figures

FIGURE 2. Distribution of Psilorhynchus brachyrhynchus (square), P. piperatus (star) and P. gokkyi (circle).

FIGURE 4. Schematic illustration of caudal-fin pigmentation patterns in Myanmar species of Psilorhynchus and in P. balitora. A. Psilorhynchus balitora, KU 29191, 45.5 mm SL. B. Psilorhynchus brachyrhynchus, NRM 40922, paratype, 45.5 mm SL. C. Psilorhynchus breviminor, ZRC 51222, holotype, 35.9 mm SL. D. Psilorhynchus gokkyi, BMNH 2010.4. 14.1, holotype, 50.7 mm SL. E. Psilorhynchus pavimentatus, UMMZ 248831, holotype, 48.7 mm SL. F. Psilorhynchus piperatus, BMNH 2010.4. 14.8, holotype, 47.7 mm SL. G. Psilorhynchus melissa, UMMZ 248829, holotype, 47.6 mm SL. H. Psilorhynchus robustus, ZRC 51111, holotype, 60.3 mm SL. Tips of caudal-fin membranes frayed or torn in majority of specimens.

FIGURE 6. Psilorhynchus piperatus, BMNH 2010.4. 14.8, holotype, 47.7 mm SL; Myanmar: Magwe Division, Man Chaung.

FIGURE 7. Man Chaung, 0.5 miles from Zinpyone village, Magwe Division, Myanmar. Type locality of Psilorhynchus piperatus.