Microsynodontis nannoculus, 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 : 27-32

Microsynodontis nannoculus sp. nov. ( Fig. 12)

Microsynodontis batesii (non Boulenger) (?) Pappenheim, 1911: 525; Roman, 1971: 131, Fig. 56.

Type material: Holotype: MRAC 173145, male, 39.1 mm SL; Equatorial Guinea: Mami River, a tributary of Kyé River; B. Roman, 5 September 1967.

Paratype: MRAC 173146, female, 35.7 mm SL; data as for holotype.

Diagnosis. Microsynodontis nannoculus can be distinguished from all congeners in having a smaller eye (10.6–12.2% SL vs. 13.1–25.7).

Description. Biometric and meristic data as in Table 6 . 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 just short of 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 3–4 long, thin branches on posterior half. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to middle of pectoral­fin base and with 3–4 long, thin branches.

Eye small 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 14–20, conical and separated from secondary teeth by distinct gap. Secondary teeth 35–40, acutely pointed and recurved; disposed in 3–4 rows. Tertiary teeth 17–23, elongate, villiform and extending over full width of premaxillae. Dentary teeth 18–19, 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,7 (2) rays and convex margin. Dorsal­fin spine short, 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 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 (1) or iv,9* (1) rays and convex margin. Pelvic­fin origin at vertical ventral to posterior end of dorsal­fin base. Pelvic fin with i,6 (2) rays and slightly convex margin; tip of appressed fin not reaching anal­fin origin. Pectoral fin with I,6 (2) rays; spine slightly curved and stout (as in Fig. 4 f). Anterior spine margin with 17– 20 small serrations along entire length of spine; serrations antrorse (distally directed) on distal two­thirds and anteriorly directed on proximal third. Posterior spine margin with 9– 10 strong serrations along entire length. Pectoral­fin margin convex posteriorly. Vertebrae 12+24=36* (1) or 13+23=36 (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: 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. 12). 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 slender, 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 anal fins hyaline and with one to two rows of elongate spots forming longitudinal brown rows. Caudal fin hyaline, with elongate brown spots forming two to three irregular columns.

Distribution. Known only from the Kyé River drainage (the Kyé River itself is a tributary of the Ntem River) in eastern Equatorial Guinea ( Fig. 13 ). Pappenheim’s (1911) record of M. batesii from the Benito River drainage may belong to this species, but I was unable to examine the specimens to verify their identity.

Etymology. From the Latin nanus, meaning small, and oculus, meaning eye. In allusion to the relatively small eye. Used as a noun in apposition.

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 ().

Tables

TABLE 6. Biometric data for M. nannoculus (n = 2).

	HOLOTYPE	PARATYPE	MEAN±SD
SL (mm)	39.1	35.7
In % SL
Predorsal length	37.1	40.1	38.6±2.12
Snout to anal	63.9	76.2	70.1±8.70
Snout to pelvic	47.6	53.8	50.7±4.38
Snout to pectoral	20.7	23.2	22.0±1.77
Dorsal­fin base length	11.5	16.0	13.8±3.18
Dorsal spine length	17.6	25.5	21.6±5.59
Anal­fin base length	16.6	12.6	14.6±2.83
Pelvic­fin length	13.6	16.0	14.8±1.70
Pectoral fin length	23.8	23.5	23.7±0.21
Pectoral spine length	19.9	22.4	21.2±1.77
Caudal total length	23.0	25.5	24.3±1.77
Adipose basal length	33.8	29.4	31.6±3.11
Adipose maximum height	5.1	5.3	5.2±0.14
Dorsal to adipose distance	18.2	17.4	17.8±0.57
Adipose to caudal peduncle	7.4	9.8	8.6±1.70
Caudal peduncle length	17.6	19.9	18.8±1.63
Caudal peduncle depth	9.2	9.8	9.5±0.42
Body depth at anus	17.6	19.0	18.3±0.99
Head length	25.1	26.3	25.7±0.85
Head width	22.5	20.4	21.5±1.48
Head depth	17.9	19.3	18.6±0.99
In % HL
Snout length	48.0	47.9	48.0±0.07
Interorbital distance	34.7	34.0	34.4±0.49
Orbit diameter	12.2	10.6	11.4±1.13
Maxillary barbel length	110.2	126.6	118.4±11.60
Inner mandibular barbel length	74.5	62.8	68.7±8.27
Outer mandibular barbel length	91.8	100.0	95.9±5.80