The Microsynodontis (Teleostei: Siluriformes: Mochokidae) of the lower Guinea region, west central Africa, with the description of eight new species
Author
Ng, Heok Hee
text
Zootaxa
2004
531
1
52
journal article
10.5281/zenodo.157924
9e7e41e3-cc57-40b7-8305-659cae0868a8
11755326
157924
Microsynodontis batesii
Boulenger, 1903
(
Fig. 1
)
Microsynodontis batesii
Boulenger, 1903
: 26
, Pl. 4 (
type
locality: Mvile River, south
Cameroon
); 1905: 50; 1911: 476, Fig. 356;
Holly, 1930
: 257
(in part);
Monod, 1928
: 202
;
Pellegrin, 1929a
: 359
; 1929b: 452;
Howes, 1980
: 168
.
Material.
AMNH
232091 (1), female:
34.6 mm
SL
;
Gabon
: Ivindo River drainage, Minkebe gold camp forest,
1°43'38.2"N
12°48'35.8"E
.
BMNH
1903.7.28.105–110 (6), 3
syntype
females:
48.8–58.3 mm
SL
, 3
syntype
males:
75.7–84.7 mm
SL
;
Cameroon
: Mvile River.
CAS
115547 (1), male:
37.7 mm
SL
;
Cameroon
: Mvila River drainage, Menyoo River, Ebolowa,
2°53'N
11°9'E
.
CAS
147487 (2), unsexed:
18.5 mm
SL
;
Cameroon
: Ntem or Campo River drainage, Mfiande and Seng Rivers.
CAS
155689 (1), male:
57.8 mm
SL
;
Cameroon
: Ntem River drainage, Mboto River at Assok,
74 km
SE of Ebolowa,
2°34'N
11°30'E
.
CAS
155691 (4),
2 females
:
52.8–53.4 mm
SL
;
2 males
: 65.5– 66.0 mm
SL
;
Cameroon
: Ntem River drainage, Mboto River at Mékomo,
37 km
E of Ebolowa,
2°37'N
11°22'E
. CU 80445 (1), male: 48.0 mm
SL
;
Gabon
: WoleuNtem province, “Bouth” creek where it crosses road from Bitam–Minvoul,
2°15'N
11°39'E
. CU 80748 (8), males:
20.3–35.4 mm
SL
;
Gabon
: WoleuNtem province, “Deghe” creek near Auberge d’Ayengbe,
2°17'N
11°33'E
.
MCZ
32521 (1), female:
59.4 mm
SL
;
Cameroon
: Nyong River.
MRAC
93085P0279–0280 (2); females,
28.2–42.6 mm
SL
;
Cameroon
: Mboro River (tributary of Ntem River) at Akonekyé,
2°28'N
11°10'E
.
MRAC
93108P 0651–0655 (5),
3 females
:
21.5–26.5 mm
SL
;
2 males
: 27.0–
29.8 mm
SL
;
Cameroon
: Mengounou River, tributary of Mboua River, in Bilizi between Befio and Ekowong,
2°32'N
12°11'E
.
MRAC
93108P0656 (1), male:
24.9 mm
SL
;
Cameroon
: river located
4 km
from Akobass in the direction of Bitche,
2°22'N
12°4'E
.
MRAC
93108P0657 (1), male:
22.8 mm
SL
;
Cameroon
: river after Aboulou in the direction of Mebang,
2°19'N
12°4'E
.
MRAC
93108P0658 (1), male: 21.0 mm
SL
;
Cameroon
: Yété River, tributary of Kom River after Mebasa and before Ngoudjieng,
2°29'N
12°13'E
.
MRAC
93108P 0 659 (1), male:
28.2 mm
SL
;
Cameroon
: Milolo River, tributary of Kom River between Esaminkou and Andoung,
2°27'N
12°20'E
.
MRAC
94028P0002 (1), male:
34.4 mm
SL
;
Cameroon
: Anga’a River, approximately
10 km
from Yaoundé,
3°52'N
11°31'E
.
MRAC
95030P
1443–1448
(6),
1 female
: 27.0 mm
SL
, 5 unsexed:
17.4–21.2 mm
SL
;
Cameroon
: first river at confluence at Mvangan, towards Nélefoup,
2°39'N
11°44'E
.
MRAC
95030P
14431448
(4), 17.4–27.0 mm
SL
,
Cameroon
: Mvong River, tributary of Kong River,
2°48'N
11°39'E
.
MRAC
95030P
1453–1454
(2),
1 male
: 26.0 mm
SL
; 1 unsexed:
17.3 mm
SL
;
Cameroon
: Otobewo’o River, tributary of Woo River, between Ekombité and Nkolenyeng,
2°40'N
11°46'E
.
RMNH
34859 (8),
6 females
:
36.1–65.6 mm
SL
;
2 males
:
49.2–74.8 mm
SL
;
Cameroon
: Lobé River, waterfalls
9 km
S of Kribi.
Diagnosis.
Microsynodontis batesii
is the largest known species of
Microsynodontis
, reaching a size of ca.
100 mm
SL (the largest specimen among all other congeners is only ca.
65 mm
SL). It can be distinguished from all congeners except
M. hirsutus
,
M. laevigatus
and
M. polli
in having a longer adipose fin (34.4–41.6% SL vs. 21.3–34.5). It differs from
M. hirsutus
in having in having a gently curved (vs. straight) dorsal spine (
Fig. 2
) and short (vs. long) tubercles on the dorsal and lateral surfaces of the head (
Fig. 3
), from
M. laevigatus
in having a serrated (vs. smooth) anterior edge of the pectoral spine (
Fig. 4
), rounded (vs. truncate) caudal fin (
Fig. 9
), and more slender caudal peduncle (5.8–9.2% SL vs. 9.3–11.4), and from
M. polli
(n=9) in having a shorter caudal fin (20.3–27.7% SL vs. 29.6–41.6).
Description.
Biometric and meristic data as in
Table 1
. Body compressed. Predorsal profile gently convex; postdorsal body sloping gently ventrally. Preanal profile horizontal. Anus and urogenital openings located at vertical through middle of pelvic fin. Skin smooth. Lateral line complete and midlateral.
Head depressed and broad, broadly rounded when viewed laterally and with rounded snout margin when viewed from above. Gill openings narrow, extending from immediately ventral to posttemporal to immediately ventral to base of pectoral spine. Gill membranes united to, and attached across, isthmus. Bony elements of dorsal surface of head covered with thin skin. Nuchal shield large and terminating posteriorly with two rounded processes on each side. Supracleithral process thin and extending just short of vertical through posteriormost tip of nuchal shield.
TABLE 1
. Biometric data for
M. batesii
(n=58).
| RANGE |
MEAN±SD |
| SL (mm) |
17.3–84.7 |
| In % SL |
| Predorsal length |
31.2–39.8 |
35.8±2.37 |
| Snout to anal |
61.6–70.6 |
67.2±2.42 |
| Snout to pelvic |
42.0–51.9 |
48.2±2.87 |
| Snout to pectoral |
18.5–24.3 |
20.5±1.81 |
| Dorsalfin base length |
10.2–14.9 |
12.4±1.43 |
| Dorsal spine length |
11.5–20.4 |
16.7±2.45 |
| Analfin base length |
12.3–16.7 |
14.4±1.19 |
| Pelvicfin length |
12.7–17.5 |
14.5±1.46 |
| Pectoral fin length |
18.9–27.0 |
22.1±2.44 |
| Pectoral spine length |
15.9–24.3 |
19.8±2.36 |
| Caudal total length |
20.3–27.7 |
23.2±2.29 |
| Adipose basal length |
34.4–41.6 |
37.8±2.18 |
| Adipose maximum height |
4.7–7.3 |
6.04±0.90 |
| Dorsal to adipose distance |
9.2–16.3 |
12.9±2.42 |
| Adipose to caudal peduncle |
7.6–10.4 |
9.0±0.96 |
| Caudal peduncle length |
14.8–19.7 |
17.7±1.42 |
| Caudal peduncle depth |
5.8–9.2 |
7.9±1.03 |
| Body depth at anus |
11.8–18.7 |
16.0±1.71 |
| Head length |
20.1–26.8 |
24.1±1.98 |
| Head width |
15.8–24.7 |
21.7±2.54 |
| Head depth |
12.7–18.8 |
16.1±1.95 |
| In % HL |
| Snout length |
42.1–48.9 |
46.0±2.33 |
| Interorbital distance |
29.1–40.7 |
34.1±3.43 |
| Orbit diameter |
14.7–19.6 |
16.3±1.34 |
| Maxillary barbel length |
90.2–144.6 |
117.13±15.66 |
| Inner mandibular barbel length |
51.2–84.7 |
64.0±9.61 |
| Outer mandibular barbel length |
78.7–130.2 |
94.8±14.43 |
Barbels in three pairs. Maxillary barbel long and slender, extending to just beyond base of last pectoralfin ray. Inner mandibularbarbel origin close to midline, extending to base of pectoral spine and with 2 short, thin branches on anterior half and 3–5 long, thin branches on posterior half. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to middle of pectoralfin base and with 3–5 long, thin branches.
FIGURE 1.
Microsynodontis batesii
: a. adult coloration, RMNH 34859, 74.8 mm SL, Cameroon: Lobé River; b. live coloration (fish from southern Cameroon, ca. 65 mm SL, not preserved), photograph courtesy of Erwin Schraml; c. juvenile coloration MRAC 93108P0657, 22.8 mm SL; Cameroon: Ntem River drainage.
FIGURE 2.
Lateral view of dorsal spines of: a.
M. hirsutus
, holotype, CU 87040, 62.0 mm SL and b. all other
Microsynodontis
(represented by
M. batesii
, CAS 155691, 62.4 mm SL). Scale bar represents 1 mm.
FIGURE 3.
Magnified view of the right ventrorbital region, showing tubercle morphology in mature males of: a.
M. hirsutus
, holotype, CU 87040, 62.0 mm SL; and b. all other
Microsynodontis
(represented by
M. batesii
, RMNH 34859, 74.8 mm SL). Both photographs were taken under identical magnification (50X). Scale bar indicates 0.5 mm.
FIGURE 4.
Dorsal view of pectoral spines of: a.
M. armatus
, holotype, CU 89392, 27.4 mm SL; b.
M. christyi
, MRAC 61801, 37.5 mm SL; c.
M. emarginatus
, paratype, CU 80567, 32.0 mm SL; d.
M. laevigatus
, paratype, CU 88265, 28.1 mm SL; e.
M. notatus
, holotype, MRAC 8051P839, 41.0 mm SL; f. all other
Microsynodontis
(represented by
M. batesii
, MRAC 93085P0280, 42.6 mm SL). Scale bar represents 1 mm.
Eye ovoid, horizontal axis longest; located entirely in dorsal half of head. Orbit without free margin.
Mouth inferior and crescentshaped; lips plicate. Oral teeth in rows on all toothbearing surfaces. Premaxillae narrow, with narrow ventral shelf and partially exposed when mouth closed. Primary teeth 10–15, conical and separated from secondary teeth by distinct gap. Secondary teeth 40–85, acutely pointed and recurved; disposed in 3–4 rows. Tertiary teeth 17–29, elongate, villiform and extending over full width of premaxillae. Dentary teeth 17–28, acutely pointed, strongly recurved and broader than secondary teeth; disposed in one or two transverse bands.
Dorsal fin located at anterior third of body, with convex margin and II,6 (39) or II,7 (3) rays. Dorsalfin spine long, stout and slightly curved; smooth on both anterior and posterior margins. Adipose fin long, extending for most of postdorsal distance; margin slightly convex for entire length and posterior end deeply incised. Caudal fin rounded, with i,6,5,i (26) or i,6,6,i (16) principal rays. Procurrent rays symmetrical and extend only slightly anterior to fin base. Analfin base located ventral to posterior half of adipose fin. Anal fin with iv,7 (30); iv,8 (9); iv,9 (2) or iv,10 (1) rays and convex margin. Pelvicfin origin at vertical ventral to posterior end of dorsalfin base. Pelvic fin with i,6 (42) rays and slightly convex margin; tip of appressed fin not reaching analfin origin. Pectoral fin with I,5,i (13); I,6 (28) or I,6,i (1) rays; spine slightly curved and stout (
Fig. 4
f). Anterior spine margin with 22–33 small serrations along entire length of spine; serrations antrorse (distally directed) on distal twothirds and anteriorly directed on proximal third. Posterior spine margin with 6–14 strong serrations along entire length. Pectoralfin margin convex posteriorly. Vertebrae 13+22=35 (6); 11+25=36 (1); 12+24=36 (4); 13+23=36 (3); 14+22=36 (2); 12+25=37 (5); 13+24=37 (4); 12+26=38 (2); 13+25=38 (7) or 14+23=37 (1).
Males with numerous tubercles on sides of head on region extending from snout to preopercle, and long genital papilla situated immediately posterior to anus. Females with fewer tubercles on sides of head, and with smaller, distally flattened genital papilla.
Coloration.
In 70% ethanol (adults larger than ca.
35 mm
SL): dorsal and lateral surfaces and of head and body medium brown, fading to cream or light grayish brown on ventral third of body, belly (with large faint brown spots), and ventral surface of head (
Fig. 1
a). Snout with a series of cream spots delineating anterior and posterior nares, sometimes coalescing to form cream band running from anterior orbital margin to tip of snout. Cheek region with one or two cream spots immediately ventral to orbit. Cream band encircling nape at supraoccipital. Dorsal third of body with series of four cream vertical barshaped marks extending beyond lateral midline of body: first at middle of dorsalfin base, second at adiposefin origin, third at middle of adiposefin base and last on caudal peduncle immediately posterior to adipose fin, sometimes encircling caudal peduncle as cream band. Ventral third of flanks with a longitudinal series of five to seven cream spots or vertical barshaped marks. Dorsal, pectoral, pelvic and analfin rays with brown spots arranged in two or three bands. Caudalfin rays with brown spots arranged in four bands and hyaline interradial membranes. Live coloration similar, with the addition of a faint dark reticulate pattern overlying the body (
Fig. 1
b).
Coloration of juveniles (smaller than ca.
35 mm
SL) similar, except for more prominent brown spotting on ventral surfaces, and larger cream markings that sometimes assume more vermiform shapes, partially coalescing to form reticulate pattern (
Fig. 1
c). Pectoral fins hyaline, with scattered brown spots. Dorsal, anal and caudal fin with brown spots arranged in transverse bands.
Distribution.
Known from the Ntem River drainage in southern
Cameroon
and northern
Gabon
, as well as the Campo, Ivindo, Lobé, Nyong and Sanaga River drainages in southern and central
Cameroon
(
Fig. 5
).
Remarks.
Although
M. batesii
appears to have a much wider distribution compared to all other
Microsynodontis
from lower
Guinea
(
Figs. 5
,
7
&
13
), it is possible that more than one species is involved in what is recognized as
M. batesii
here. In particular, the populations from the northernmost extent of its distribution (i.e. from the Nyong and Sanaga River drainages) should be further studied to verify their conspecificity with the material from southern
Cameroon
and northern
Gabon
, but the paucity of relevant material available for study does not allow for more a more conclusive test of this hypothesis.