Microsynodontis notatus, 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 : 35-39

Microsynodontis notatus sp. nov. ( Fig. 15 )

Microsynodontis batesii (non Boulenger) Pellegrin, 1909: 66; 1915: 503.

Type material: Holotype: MRAC 80­51­P­839, male, 41.0 mm SL: Gabon: Ezanga River, about midway between Lake Ezanga and Ogooué mainstream; T. R. Roberts, 10 September 1978.

Paratypes: MRAC 73­2­P­ 1906–1910 (5), 3 females: 26.9–31.0 mm SL; 2 males: 33.3–40.0 mm SL; Gabon: Lake Onangue, Mountsomanie; D. F. E. Thys van den Audenaerde, 28 August 1981. MRAC 80­51­P­17 (1), female: 53.6 mm SL; Gabon: Ogooué River, mainstream at Lambaréné; T. R. Roberts, 30 July 1978. MRAC 80­51­P­840–866, 16 females: 22.1–39.4 mm SL; 11 males: 24.8–43.7 mm SL; data as for holotype.

Diagnosis. Microsynodontis notatus can be distinguished from all congeners except for M. christyi and M. laevigatus in having a deeper caudal peduncle (9.6–11.9% SL vs. 5.8–9.8). It differs from M. christyi in having a larger eye (17.2–25.7% HL vs. 13.6–17.9) and from M. laevigatus in having a serrated (vs. smooth) anterior edge of the pectoral spine ( Fig. 4 ) and a rounded (vs. truncate) caudal fin ( Fig. 9 ). It also differs from all congeners in frequently having numerous faint, dark brown elongate spots on the body (vs. spots always absent).

Description. Biometric and meristic data as in Table 8 . Body compressed. Predorsal profile steep; 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, 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 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 11–14, conical and separated from secondary teeth by distinct gap. Secondary teeth 30–40, acutely pointed and recurved; disposed in 3–4 rows. Tertiary teeth 16–20, elongate, villiform and extending over full width of premaxillae. Dentary teeth 15–19, 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,6* (14) or II,7 (20) 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,5,6,i (1) or i,6,6,i* (33) 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 (1); iii,8 (4); iv,7* (11) or iv,8 (18) rays and convex margin. Pelvic­fin origin at vertical ventral to posterior end of dorsal­fin base. Pelvic fin with i,6 (34) rays and slightly convex margin; tip of appressed fin not reaching anal­fin origin. Pectoral fin with I,6 *(32) or I,6,i (2) rays; spine slightly curved and stout ( Fig. 4 e). Anterior spine margin with 3–16 small serrations along entire length of spine; serrations antrorse (distally directed) on distal two­thirds and anteriorly directed on proximal third. Posterior spine margin with 6–12 strong serrations along entire length. Pectoral­fin margin convex posteriorly. Vertebrae 12+23 (2); 12+24 (6); 13+22 (1); 13+23* (10); 13+24 (12) or 14+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 light to medium brown, fading to cream on belly and ventral surfaces ( Fig. 15 ). Dorsal and lateral surfaces of head and body frequently with dark brown elongate spots evenly distributed and forming a reticulate pattern. Snout with a series of cream spots delineating anterior and posterior nares. 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 five cream 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, fourth at posteriormost point 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 four to seven cream spots or vertical bar­shaped marks. Adipose fin brown, with an extensive hyaline margin and sometimes with dark brown spots and vermiform 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 lower Ogooué River in Gabon ( Fig. 5 ).

Etymology. From the Latin notatus , meaning marked. In reference to the dark elongate spots frequently present in 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 5. Map showing the distribution of M. batesii (), M. laevigatus () and M. notatus ().

FIGURE 9. Lateral view of caudal fins showing: a. emarginate fin (condition in Microsynodontis emarginatus, CU 89393, holotype, 33.4 mm SL); b. rounded fin (other Microsynodontis species, represented by M. batesii, CU 80748, 33.2 mm SL); c. truncate fin (condition in M. laevigatus and M. lamberti, represented by M. laevigatus, CU 88265, paratype, 22.8 mm SL).

FIGURE 15. Microsynodontis notatus, holotype, MRAC 80 ­ 51 ­ P­ 839, 41.0 mm SL; Gabon: Ogooué River drainage.

Tables

TABLE 8. Biometric data for M. notatus (n = 34).

	HOLOTYPE	RANGE	MEAN±SD
SL (mm)	41.0	22.1–53.6
In % SL
Predorsal length	33.2	33.2–40.4	36.7±1.63
Snout to anal	63.4	63.1–70.4	66.3±1.95
Snout to pelvic	45.9	45.2–53.2	48.8±1.61
Snout to pectoral	16.6	16.6–22.7	20.1±1.57
Dorsal­fin base length	14.1	12.5–17.0	14.8±1.21
Dorsal spine length	17.3	13.0–23.0	17.1±2.32
Anal­fin base length	13.4	12.1–17.1	14.5±1.23
Pelvic­fin length	14.9	10.0–19.3	15.1±1.69
Pectoral fin length	19.5	19.5–28.6	24.0±2.15
Pectoral spine length	24.4	18.5–25.7	21.0±1.73
Caudal total length	24.9	18.3–26.1	22.1±2.01
Adipose basal length	33.2	28.5–34.5	31.0±1.71
Adipose maximum height	6.1	3.8–6.7	5.6±0.66
Dorsal to adipose distance	15.9	9.1–16.5	13.2±1.88
Adipose to caudal peduncle	11.2	9.3–13.6	11.1±1.10
Caudal peduncle length	19.5	14.2–20.7	17.8±1.47
Caudal peduncle depth	10.2	9.6–11.9	10.6±0.51
Body depth at anus	16.3	14.9–21.5	17.5±1.28
Head length	23.7	23.2–29.4	26.2±1.46
Head width	21.2	21.2–26.7	24.2±1.40
Head depth	16.1	16.1–20.4	18.0±1.06
In % HL
Snout length	43.3	38.3–48.4	44.4±2.78
Interorbital distance	37.1	33.0–46.8	38.8±3.29
Orbit diameter	21.6	17.2–25.7	20.8±2.18
Maxillary barbel length	127.8	95.2–155.8	112.2±13.70
Inner mandibular barbel length	54.6	37.1–89.3	59.4±10.35
Outer mandibular barbel length	111.3	66.0–111.3	89.5±11.3