Microsynodontis vigilis, Ng, Heok Hee, 2004

Ng, Heok Hee, 2004, The Microsynodontis (Teleostei: Siluriformes: Mochokidae) of the lower Guinea region, west central Africa, with the description of eight new species, Zootaxa 531, pp. 1-52 : 39-43

Microsynodontis vigilis sp. nov. ( Fig. 16 )

Type material. Holotype: CU 87039, male, 62.0 mm SL; Gabon: Moyen­Ogooué province, 12 km N of Lambaréné, branch of Nzorbang creek near village of same name, 0°34'6.2"S 10°12'46.4"E; C. D. Hopkins et al., 18 July 1999.

Paratypes: CU 80133 (17): 8 females: 30.5–48.0 mm SL; 9 males: 31.5–58.9 mm SL; data as for holotype.

Diagnosis. Microsynodontis vigilis can be distinguished from all congeners in having a longer supracleithral process (reaching to vertical through the posteriormost tip of nuchal shield vs. not reaching). It further differs from all other congeners except for M. armatus and M. lamberti in having a shorter adipose fin (22.0–28.2% SL vs. 27.9–41.6), and except for M. emarginatus , M. lamberti , and M. notatus , in having a larger eye (19.3–25.0% HL vs. 10.6–19.6). Microsynodontis vigilis can be further distinguished from M. lamberti in having a serrated (vs. smooth) anterior edge of the pectoral spine and a round (vs. truncate) caudal fin.

Description. Biometric and meristic data as in Table 9 . 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, acutely 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, extending to vertical through posteriormost tip of nuchal shield.

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.

Eye large and 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 13–14, conical and separated from secondary teeth by distinct gap. Secondary teeth 40–85, acutely pointed and recurved; disposed in 3–4 rows. Tertiary teeth 22–26, elongate, villiform and extending over full width of premaxillae. Dentary teeth 17–27, 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 II,6 (1) or II,7* (17) rays and convex margin. Dorsal­fin spine long, stout and slightly curved; smooth on both anterior and posterior margins. Adipose fin moderately long; margin slightly convex for entire length and posterior end deeply incised. Caudal fin rounded, with i,6,6,i (18) 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 iii,7 (2); iii,8* (3); iv,7 (10) or iv,8 (3) rays and convex margin. Pelvic­fin origin at vertical ventral to posterior end of dorsalfin base. Pelvic fin with i,6 (18) rays and slightly convex margin; tip of appressed fin not reaching anal­fin origin. Pectoral fin with I,5 (2); I,6 (14) or I,6,i* (2) rays; spine slightly curved and stout (as in Fig. 4 f). Anterior spine margin with 22–28 small serrations along entire length of spine; serrations antrorse (distally directed) on distal two­thirds and anteriorly directed on proximal third. Posterior spine margin with 8–13 strong serrations along entire length. Pectoral­fin margin convex posteriorly. Vertebrae 11+24 (1); 13+23 (7); 13+24* (6); 14+22 (1) or14+23 (3).

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: dorsal and lateral surfaces and of head and body dark chocolate brown, fading to light brown on belly ( Fig. 16 ). Snout with a series of light yellow spots delineating anterior and posterior nares. Cheek region with one or two light yellow spots immediately ventral to orbit. Light yellow band encircling nape at supraoccipital. Dorsal third of body with series of four light yellow vertical bar­shaped marks extending to 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 light yellow band. Ventral third of flanks with a longitudinal series of four to seven light yellow spots or vertical bar­shaped marks. Dorsal fin with dark chocolate brown base and one to two rows of elongate spots forming longitudinal dark chocolate brown rows. Pectoral, pelvic and anal fins with hyaline bases and similarly marked. Caudal fin hyaline, with elongate brown spots forming two to three irregular columns.

Distribution. Known only from the lower Ogooué River drainage in Gabon ( Fig. 13 ).

Habitat. The type locality is a forest stream with a sandy bottom. Water temperature was 24.4°C and the pH was 5.5. Syntopic fish included: Mormyridae : Brienomyrus sp., Mormyrops zanclirostris , Stomatorhinus spp.; Characidae : Alestes sp., Brycinus sp.; Ditichodontidae: Nannocharax sp.; Cyprinidae : Barbus spp.; Amphiliidae : Amphilius nigricaudatus , Phractura sp.; Claroteidae : Anaspidoglanis macrostoma ; Malapteruridae : Malapterurus beninensis ; Mochokidae : Synodontis sp.; Cyprinodontidae : Epiplatys dageti , Plataplochilus chalcopyrus ; Channidae : Parachanna obscura ; Cichlidae : Hemichromis sp.

Etymology. From the Latin vigilis , meaning watchful. In allusion to the relatively large eyes of this species. Used as an adjective.

Figures

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 80 ­ 51 ­ P­ 839, 41.0 mm SL; f. all other Microsynodontis (represented by M. batesii, MRAC 93 ­ 085 ­ P­ 0280, 42.6 mm SL). Scale bar represents 1 mm.

FIGURE 13. Map showing distributions of M. nannoculus (), M. nasutus (˖) and M. vigilis ().

FIGURE 16. Microsynodontis vigilis, holotype, CU 87039, 62.0 mm SL; Gabon: Ogooué River drainage.

Tables

TABLE 9. Biometric data for M. vigilis (n = 18).

	HOLOTYPE	RANGE	MEAN±SD
SL (mm)	62.0	30.5–62.0
In % SL
Predorsal length	32.7	32.7–39.9	35.8±1.88
Snout to anal	64.4	64.4–71.5	68.3±1.86
Snout to pelvic	46.5	45.5–51.0	48.8±1.63
Snout to pectoral	19.0	17.9–21.4	19.8±1.06
Dorsal­fin base length	14.5	11.4–17.9	14.5±1.34
Dorsal spine length	14.4	13.4–19.6	16.1±1.63
Anal­fin base length	13.7	12.4–15.5	13.7±0.89
Pelvic­fin length	16.5	13.8–17.9	15.4±0.98
Pectoral fin length	21.0	19.5–27.2	23.5±2.28
Pectoral spine length	18.1	17.1–22.9	20.2±1.63
Caudal total length	25.3	19.0–28.5	23.2±2.47
Adipose basal length	27.6	22.0–28.2	26.4±1.45
Adipose maximum height	4.7	4.7–7.1	5.8±0.71
Dorsal to adipose distance	17.9	11.5–20.8	16.4±2.32
Adipose to caudal peduncle	10.2	8.6–11.0	9.7±0.57
Caudal peduncle length	19.4	14.8–19.4	17.1±1.12
Caudal peduncle depth	8.7	8.1–9.8	9.0±0.50
Body depth at anus	16.1	15.4–19.2	17.2±1.17
Head length	23.7	23.7–28.0	26.1±1.25
Head width	20.3	20.3–24.4	22.6±1.35
Head depth	15.6	15.3–18.0	16.7±0.85
In % HL
Snout length	46.3	34.7–47.6	44.1±3.66
Interorbital distance	34.0	28.6–37.8	34.6±2.50
Orbit diameter	21.8	21.3–25.0	22.9±1.10
Maxillary barbel length	109.5	75.6–132.8	106.2±14.84
Inner mandibular barbel length	55.8	25.6–72.7	51.0±11.13
Outer mandibular barbel length	78.2	56.1–104.7	78.3±11.9