Three New Species Of Freshwater Halfbeaks (Teleostei: Zenarchopteridae: Hemirhamphodon) From Borneo
Author
Tan, Heok Hui
Author
Lim, Kelvin K. P.
text
Raffles Bulletin of Zoology
2013
2013-08-30
61
2
735
747
journal article
10.5281/zenodo.5352848
2345-7600
5352848
Hemirhamphodon sesamum
,
new species
(
Figs. 1A–D
,
2A–C
,
3A, B
,
4
,
5A–D
,
6A–B
)
Material examined
.
—
Holotype
–
MZB
17209,
36.7 mm
SL, male;
Indonesia
:
South Kalimantan
:
Batulicin
basin; stream at
Simpang Alok
, along road from
Batulicin
to
Mantewe
,
Desa Gunung Raya
(
84 m
asl
);
H. Tommy
et al.,
14 Sep.2011
.
Paratypes
–
MZB
17210,
7 ex.
,
19.2–44.4 mm
SL; same locality as holotype
. –
ZRC
54009,
37 ex.
,
18.2–46.4 mm
SL;
Indonesia
:
South Kalimantan
:
Cantung
basin; north of
Batulicin
,
Sei Kupang area
, amidst limestone hills (
24 m
asl
, pH 8.0);
H. Tommy
et al.,
12 Sep.2011
. –
ZRC
54010,
10 ex.
,
13.4–44.6 mm
SL;
Indonesia
:
South Kalimantan
:
Batulicin
basin; hill stream at foothills of
Gunung Kukusan
on northeast side (
52 m
asl
);
H. Tommy
et al.,
12 Sep.2011
. –
ZRC
54013,
2 ex.
,
41.4–47.4 mm
SL;
Indonesia
:
South Kalimantan
: north of
Batulicin
;
T
.
Idei
, 2004. CMK 16796,
4 ex.
,
34.5–46.4 mm
SL;
Indonesia
:
South Kalimantan
:
25 km
south of
Damar Datar
,
Koto
to
Batulian
;
T
.
Idei
,
12 Oct.2000
.
Diagnosis
.
—
Hemirhamphodon sesamum
differs from all congeners in having the following suite of characters: 1) Dorsal fin with melanophores in two distinct sizes – for males in life (
Figs. 2A
,
4
), first 6 to 7 rays distal one-third to half with yellow suffused throughout the rays and interradial membrane, with iridescent red margin; intense black pigments on the mid-section of interradial membrane between first 3 rays; red pigments on the mid-section of interradial membrane between 6 to 11 rays; rest of fin hyaline. For males in preservative (
Fig. 2B, C
), colour pattern as above, but the iridescent red margin is absent. For females in life (
Fig. 3A
), first 6 to 7 rays suffused with pale yellow, with iridescent red margin; small patches of black pigments on the middle section of the interradial membrane of first 6 to 7 rays; rest of fin hyaline. For females in preservative (
Fig. 3B
), colour pattern as above, but the iridescent red margin is absent. Black patches on anterior portion of dorsal fin present in specimens
20 mm
SL or larger. 2) Unique dorsal fin morphology in the males (
Fig. 4
) – distal portions of first 6 to 7 rays elongated, free of interradial membrane, projected into filaments up to twice the depth of the dorsal fin; adpressed fin rays reaching caudal-fin base and beyond. 3) Unique colouration on lower jaw; for males in life (
Fig. 5A
), upper jaw with corresponding portion of lower jaw yellow; dorsal surface of exposed lower jaw bluish, dermal flange below middle section of lower jaw bright red with blue lower margin, tip of lower jaw to region below upper jaw red; dermal flange of lower jaw with distinct black ventral margin from tip to region directly below eye. Males in preservative (
Fig. 5B
) exhibit similar colour pattern but colours are subdued or faded. Females in life (
Fig. 5C
) have similar colour pattern as male but colours are comparatively less intense. For females in preservative (
Fig. 5D
), the red band on the dermal flange of the lower jaw is replaced by yellow. 4) Males with the fourth anal-fin ray distinctly enlarged (
Figs. 1A, B
,
2A–C
,
6A
), and third, fourth and eighth anal-fin rays branched; females with third and fourth anal-fin rays branched (
Figs. 1C, D
,
3A, B
,
6B
). 5) Pelvic-fin origin anterior to dorsal-fin origin. 6) Dorsal-fin rays 13 or 14 (mode 13).
Description
.
— See
Figs. 1–5
for general appearance and
Table 1
for morphometric data.
Head short (head length 24.3–28.7% SL) and body slender and long (body depth 8.6–11.9% SL, caudal peduncle depth 4.7–5.7% SL, body length 70.5–75.3% SL). Lower jaw about half of body length (48.0–63.8% BL), about 1.2–1.7 times head length; usually straight, tip bent downwards in a few specimens; dermal flange of lower jaw on male deeper than that on female. Dorsal-fin origin anterior to anal-fin origin, posterior to pelvic-fin origin, situated nearer to caudal fin (predorsal length 71.7–76.9% SL), dorsal-fin base short (dorsal-fin base length 18.9–24.5% SL); dorsal-fin rays 13 or 14 (mode 13); male with first 6 to 7 dorsal-fin rays elongated into filaments, adpressed rays reaching caudal-fin base and beyond. Caudal fin elongate, rounded, caudal-fin rays 26. Anal-fin rays 8 (last ray split to base), with short base (5.8–9.2% SL), male with distinct posterior projection on base of fourth fin ray, adpressed elongated anal-fin ray reaching caudal-fin base, with branched ray on rays 3, 4 and 8, andropodium developed on ray 5 to 8, rays 5 and 8 thickened throughout (
Fig. 5A
); female with branched ray on rays 3 and 4 (
Fig. 5B
). Pelvic-fin rays 6–7, fins are adpressed to body, male with longer inner rays, adpressed rays reaching anal-fin origin; female with shorter rays, adpressed rays not reaching anus. Pectoral-fin rays 8, rounded. Precaudal vertebrae 23–26, caudal vertebrae 14–16; total vertebrae 38–41 (mode 40, n = 20). First gill arch with up to 13 gill rakers. Maximum size
47.4 mm
SL.
Fig. 1. Live and preserved colouration of
H. sesamum
: A, MZB 17209, 36.7 mm SL, live male holotype; B, ZRC 54009, 47.0 mm SL, preserved male; C, MZB 17210, 44.4 mm SL, live female; D, ZRC 54009, 44.3 mm SL, preserved female (not to scale).
Fig. 2. Dorsal fin and anal fin colouration of male
H. sesamum
: A, live holotype, MZB 17209, 36.7 mm SL; B, ZRC 54009, 47.0 mm SL (white background); C, ZRC 54009, 47.0 mm SL (black background).
Table 1. Morphometric data of
Hemirhamphodon sesamum
,
H. byssus
, and
H. kecil
.
|
H. sesamum
|
H. byssus
|
H. kecil
|
| ZRC 54009, ZRC 54010 |
ZRC 37832, ZRC 39508 |
ZRC 45682 |
| SL (mm) |
34.8–46.9 |
45.6–70.3 |
31.0–40.8 |
| Sample size |
20 |
10 |
10 |
| % SL |
| Total length |
117.7–123.1 |
118.5–123.0 |
114.2–123.8 |
| Body length |
70.5–75.3 |
68.9–72.2 |
71.4–74.9 |
| Predorsal-fin length |
71.7–76.9 |
70.6–75.5 |
70.6–74.9 |
| Preanal-fin length |
80.0–83.2 |
77.0–82.7 |
75.8–82.0 |
| Prepelvic-fin length |
63.5–68.1 |
62.0–65.5 |
59.4–64.9 |
| Head length |
24.3–28.7 |
27.3–29.4 |
25.1–28.1 |
| Body depth at anus |
8.6–11.9 |
9.0–13.1 |
9.3–11.1 |
| Caudal peduncle depth |
4.7–5.7 |
4.8–6.3 |
4.4–5.8 |
| Caudal peduncle length |
9.8–13.1 |
11.1–13.7 |
10.0–11.7 |
| Dorsal-fin base length |
18.9–24.5 |
20.8–24.3 |
21.5–24.9 |
| Anal-fin base length |
5.8–9.2 |
6.0–7.7 |
6.4–8.4 |
| Lower jaw length |
35.7–45.7 |
39.1–47.6 |
32.1–42.9 |
| Orbital diameter |
5.3–6.8 |
5.7–6.9 |
5.7–6.8 |
| Interorbital width |
6.7–8.0 |
7.2–8.1 |
6.4–7.2 |
| % HL |
| Lower jaw length |
124.4–169.2 |
135.3–170.6 |
118.4–156.0 |
| Orbital diameter |
20.2–26.0 |
19.9–23.8 |
20.7–25.6 |
| Interorbital width |
24.4–29.1 |
25.9–29.1 |
23.8–27.9 |
Colouration in life
.
— See
Figs. 1A, 1C
,
2A
,
3A
,
5A, 5C
. Adult male – Head brown on dorsum and sides, ventrum cream. Upper jaw yellow with corresponding portion of lower jaw also yellow; dorsal surface of exposed lower jaw bluish, middle section of dermal flange on lower jaw red with blue lower margin, red section from tip to region below upper jaw; ventrum of lower jaw flange with distinct black margin from tip to region directly below eye. Eye with upper half of iris pale reddish. Operculum with scattering of melanophores, and pinkish on posterior part. Body with brown dorsal stripe, dorsum pinkish and sides yellowish brown, ventrum cream with thin reddish ventral stripe. Dorsal fin with first 6 to 7 rays distal one-third to half with yellow suffused throughout the rays and interradial membrane; intense black pigments on the mid-section of interradial membrane between first 3 rays; red pigments on the mid-section of interradial membrane between 6 to 11 rays; rest of fin hyaline. Caudal, anal and pelvic fins with bright red margin; anal fin with bright red blotch on middle of andropodium. Pectoral fins hyaline.
Adult female: colouration similar, but less intense. Dorsal fin with first 6 to 7 rays suffused with pale yellow, with iridescent red margin; small patches of black pigments on the middle section of the interradial membrane of first 6 to 7 rays; rest of fin hyaline.
Colouration in preservative
.
— See
Figs. 1B, D
,
2B, C
,
3B
,
5B, D
.
Fig. 3. Dorsal fin and anal fin colouration of female
H. sesamum
: A, live paratype, MZB 17210 (with damaged dorsal and caudal fins), 44.4 mm SL; B, ZRC 54009, 44.3 mm SL.
Adult male – Head brown on dorsum and sides, ventrum cream. Upper jaw yellow with corresponding portion of lower jaw also yellow; dorsal surface of exposed lower jaw bluish, middle section of dermal flange on lower jaw red with blue lower margin, red section from tip to region below upper jaw; ventrum of lower jaw flange with distinct black margin from tip to region directly below eye. Eye with upper half of iris pale reddish. Operculum with scattered melanophores, pinkish on posterior part. Body with brown dorsal stripe, dorsum pinkish and sides yellowish brown, ventrum cream with thin reddish ventral stripe (may be faint on specimens preserved for a long time). Dorsal fin with first 6 to 7 rays and distal one-third to half suffused with yellow throughout the rays and interradial membrane; intense black pigments on the mid-section of interradial membrane between first 3 rays; red pigments on the mid-section of interradial membrane between 6 to 11 rays; rest of fin hyaline. Caudal, anal, pelvic and pectoral fins hyaline.
Adult female – colouration as for male, but subdued. All fins hyaline. Black patches on anterior portion of dorsal fin in specimens larger than or equal to
20 mm
SL.
Distribution
.
—
Hemirhamphodon sesamum
is currently known only from
South Kalimantan
, Indonesian Borneo, in lowland drainages of the Batulicin and Cantung basins that drain eastwards into the Makassar Strait (
Fig. 7
).
Fig. 4. Dorsal fin morphology of freshly preserved
H. sesamum
male, ZRC 54009, 47.0 mm SL.
Fig. 6. Radiographs of anal fin of
H. sesamum
: A, MZB 17209, holotype, 36.7 mm SL male; B, MZB 17210, paratype, 44.4 mm SL female.
Fig. 5. Lower jaw colouration of
H. sesamum
: A, MZB 17209, 36.7 mm SL, live male holotype; B, ZRC 54009, 47.0 mm SL, preserved male; C, MZB 17210, 44.4 mm SL, live female; D, ZRC 54009, 44.3 mm SL, preserved female.
Fig. 7. Distribution of
H. sesamum
(solid circle),
H. byssus
(solid square) and
H. kecil
(hollow circle) in Borneo.
Field notes
.
—
Hemirhamphodon sesamum
inhabits clear flowing waters of small streams, about
2–5 m
wide and up to
2 m
deep, with sand and gravel bottoms (see
Fig. 8
). It tends to form small groups of 3 to 5 individuals at the surface, preferring quiet pools near or under overhanging bank vegetation. Syntopic ichthyofauna includes:
Hampala macrolepidota
,
Osteochilus
cf.
waandersii
,
Rasbora dies
,
R. elegans
,
R. lacrimula
,
Systomus anchisporus
,
S. banksi
(Cyprinidae)
,
Balitoropsis stephensoni
,
Homalopteroides nebulosus
(Balitoridae)
,
Nemacheilus
cf.
spiniferus
(Nemacheilidae)
,
Betta edithae
(Osphronemidae)
,
Channa lucius
(Channidae)
, and
Macrognathus maculatus
(Mastacembelidae)
.
Etymology
.
— The species name refers to the minute oily seeds of the
Sesamum
plant (
Pedaliaceae
); in allusion to the small black spots/dashes on the dorsal fin with which resemble black sesame seeds. Used as a noun in apposition.
Comparisons with congeners
.
—
Hemirhamphodon sesamum
shares with
H. pogonognathus
,
H. kuekenthali
,
H. byssus
, and
H. kecil
a posterior projection on the fourth anal-fin ray, a similar range of dorsal-fin rays (12–17) and a similar number of vertebrae (37–44).
Hemirhamphodon sesame
further shares with
H. kuekenthali
and
H. byssus
two types
of melanophore on the dorsal fin.
Hemirhamphodon sesamum
seems to be most closely related to
H. kuekenthali
in terms of external morphology. The current distribution of
H. kuekenthali
within Borneo (
Kottelat & Lim, 1995
; pers. obs.) is from central to northern
Sarawak
and
Brunei Darussalam
. While
H. sesamum
is currently known only from the southernmost tip of Borneo. It seems to represent a vicariant distribution. The ichthyofauna of the short coastal basins in South Kalimantan draining into the Makassar Straits is poorly known.As evident from other parts of Southeast Asia where short coastal basins are present, such as the western coast of Sumatra (
Lumbantobing, 2010
), the rate of endemism is expected to be relatively high.