Psilorhynchus gokkyi, 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 : 42-45

Psilorhynchus gokkyi , new species

( Figures 8 & 9 )

Holotype. BMNH 2010.4.14.1, male, 50.7 mm SL; Myanmar: Magwe Division, Pani Chaung (Ayeyarwaddy River drainage), near Gokkyi village, 19° 49' 20" N, 94° 26' 8" E, 22 November 2009, R. Britz et al.

Paratypes. BMNH 2010.4.14.2-7, 6, 39.5–54.7 mm SL; same data as holotype. BMNH 2010.7.20.1-6, 6, 43.0– 55.8 mm SL; same data as holotype.

Diagnosis. A species of Psilorhynchus distinguished from all other members of the genus by the presence (vs. absence) of a deep notch situated at the level of the ethmoid region, visible as a square step-like division between the snout and the head in lateral view and a deep groove in dorsal view. Psilorhynchus gokkyi is further distinguished from members of this group by the following combination of characters: snout length 51–57% HL; ventral surface between paired fins with a broad triangular scale-less patch; branched dorsal-fin rays 9–10; unbranched pectoral-fin rays 5–6; caudal-fin rays 10+9; lateral-line scales 32–34; 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 dorsal surface, in contact with the round to squarish dark brown blotches, arranged in a longitudinal row on flank; caudal fin with an irregular pigmentation pattern, most prominent along lower lobe.

Description. General body shape as in Figures 8–9 . Morphometric and meristic data are listed in Table 3 . As described for P. brachyrhynchus , but with the following differences. Snout long, contributing to 51–57% of head length. Ethmoid region with a deep notch, visible in dorsal view as a deep groove anterior to nostrils and as a square step-like division between snout and head in lateral view. Dorsal-fin rays iii.9 (6) or iii.10 (1). Pectoral-fin rays vi.10 (4), v.11 (2) or vi.11 (2). Pectoral fin reaching two or three scale rows anterior to pelvicfin origin when depressed. Scales large, 32(4), 33(2) or 34(1) along lateral line, plus 2(4) or 3(3) on base of caudal fin. 11(4), 12(2) or 13(1) predorsal scales, 8(1), 9(5) or 10(1) scales between anus and anal-fin origin. Ventral surface with a broad triangular scale-less patch between paired fins. Total number of vertebrae 34, consisting of 19+15(5) or 18+16(2) abdominal and caudal vertebrae.

Coloration. As described for P. brachyrhynchus with the following differences. Dorsal fin weakly marked with a proximal stripe running along bases 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 with a weak irregular vertical black bar across center ( Fig. 4 D). Lower lobe of caudal fin additionally speckled with small dense clusters of melanophores that gradually decrease in size posteriorly ( Fig. 4 D).

In life ( Fig. 9 ) background colour light creamy brown. Dorsal saddles, round-squarish blotches, arranged in a longitudinal row on flank, head and snout markings, and markings on lower lobe of caudal fin dark brown. Scales on lateral body sides with a silvery iridescent sheen. Paired and median fin markings, excluding those on lower lobe of caudal fin, indistinct.

Distribution and habitat. Known to date only from the type locality ( Fig. 2 ). At the type locality, Pani Chaung is a swift-flowing stream with dense bank and overhanging vegetation, and a substrate of sand, gravel and small boulders ( Fig. 10 ).

Etymology. Named after Gokkyi , a small village above the type locality, to honour the hospitality and help extended to the second author during his collection trip in November 2009. A noun in apposition.

Remarks. Psilorhynchus gokkyi is easily distinguished from all other members of the genus by the presence (vs. absence) of its deep notch in the ethmoid region, visible in dorsal view as a deep groove just anterior to the nostrils and as a square step-like division between the snout and the head in lateral view. Amongst other members of Psilorhynchus , P. gokkyi is most similar in terms of general appearance to P. amplicephalus , P. balitora , P. brachyrhynchus , P. breviminor , P. nepalensis , P. pavimentatus , P. p i p e r a t u s and P. rahmani . Psilorhynchus gokkyi is distinguished from P. amplicephalus , P. balitora , P. nepalensis , P. pavimentatus and P. piperatus by having more caudal-fin rays (10+9 vs. 8–9+ 7–8 in P. balitora , 9+ 8 in P. amplicephalus and P. nepalensis , and 9+ 9 in P. pavimentatus and P. piperatus ). It is distinguished from P. brachyrhynchus and P. rahmani by its longer snout (snout length 51–57% vs. 43–48% in P. brachyrhynchus and 46–50 in P. rahmani ), and from P. breviminor by it slightly longer caudal peduncle (caudal peduncle length 12–13% vs. 10–12). It is further distinguished from P. balitora by possessing a broad, rectangular scaleless patch on its ventral surface between the paired fins (vs. ventral surface between paired fins completely scaled).

The type locality of P. gokkyi, Pani Chaung , is close to the type locality of Channa ornatipinnis, Waloun Chaung. The latter is a tributary of Pani Chaung. Waloun Chaung was erroneously reported by Britz (2007) to be in Rakhine State, but it is actually located in Magwe Division.

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 8. Psilorhynchus gokkyi, BMNH 2010.4. 14.1, holotype, male, 50.7 mm SL; Myanmar: Magwe Division, Pani Chaung.

FIGURE 9. Psilorhynchus gokkyi, BMNH 2010.4.14.2 - 7, paratype. Myanmar: Magwe Division, Pani Chaung.

FIGURE 10. Pani Chaung, near Gokkyi village, Magwe Division, Myanmar. Type locality of Psilorhynchus gokkyi.

Tables

TABLE 3. Selected morphometric and meristic date for Psilorhynchus gokkyi holotype and six paratypes.

Standard length (mm)	% of standard length	Holotype 50.7	Range 39.5–54.7	Mean	St.Dev.
% of standard length
Body depth	20.7	18.9–20.7	19.8	0.7
Head length	22.9	20.4–22.9	21.7	0.8
Pre-dorsal length	50.3	50.1–51.6	50.5	0.5
Pre-pectoral length	20.7	19.1–20.7	20.4	0.7
Pre-pelvic length	48.3	48.0–50.4	49.3	1.0
Pre-anal length	79.3	77.9–81.0	79.1	1.0
Snout to anus length	57.6	57.6–60.1	59.0	1.1
Anus to anal fin length	23.1	19.7–23.1	21.0	1.0
Caudal-peduncle length	12.6	12.4–13.3	12.7	0.3
Caudal-peduncle depth	9.7	8.6–9.8	9.2	0.4
Caudal-peduncle width	3.4	2.8–4.0	3.2	0.4
Pectoral-fin length	24.5	23.4–27.3	25.0	1.2
Pelvic-fin length	20.3	20.1–22.8	21.3	1.0
Length of last unbranched anal-fin ray	18.5	15.9–18.5	17.2	0.9
Length of last unbranched dorsal-fin ray	22.9	21.8–23.6	22.7	0.6
% of head length
Head width	64.7	64.0–71.6	66.6	2.6
Head depth	52.6	50.9–56.1	53.8	1.7
Eye diameter	27.6	27.0–32.2	29.2	1.8
Snout Length	53.4	51.7–57.0	55.1	1.9
Interorbital width	38.8	37.5–45.2	40.4	3.4
Mouth width	28.4	28.4–34.5	30.9	2.0
Dorsal-fin rays	iii.9	iii.9–10
Anal-fin rays	ii.6	ii.5–6
Principal caudal fin-rays	10+9	-
Pectoral-fin rays	v.11	v–vi.10–11
Pelvic-fin rays	ii.7	-
Lateral-line scales	34	32–34
Scales between dorsal and pelvic fins	2	2–3
Circumpeduncular-scale rows	10	-
Preanal-scale rows	9	8–9
Predorsal-scale rows	11	11–13