Three new species of Psilorhynchus from the Ayeyarwaddy River drainage, Myanmar (Teleostei: Psilorhynchidae)
Author
Conway, Kevin W.
Author
Britz, Ralf
text
Zootaxa
2010
2616
31
47
journal article
10.5281/zenodo.197944
f821c77c-a895-4e82-ac0c-0daa618ba83b
1175-5326
197944
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).
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.
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.
TABLE 3.
Selected morphometric and meristic date for
Psilorhynchus gokkyi
holotype and six paratypes.
| Standard length (mm) |
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 |
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
).
FIGURE 10.
Pani Chaung, near
Gokkyi
village, Magwe Division, Myanmar. Type locality of
Psilorhynchus gokkyi
.
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.