Microsynodontis batesii Boulenger, 1903
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|Microsynodontis batesii Boulenger, 1903|
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, 1929 a: 359; 1929 b: 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 32521View Materials (1), female: 59.4 mm SL; Cameroon: Nyong River. MRAC 93 085P0279–0280 (2); females, 28.2–42.6 mm SL; Cameroon: Mboro River (tributary of Ntem River) at Akonekyé, 2 ° 28 'N 11 ° 10 'E. MRAC 93108 P 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 93108 P0656 (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 93108 P0657 (1), male: 22.8 mm SL; Cameroon: river after Aboulou in the direction of Mebang, 2 ° 19 'N 12 ° 4 'E. MRAC 93108 P0658 (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 93108 P 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 94 028P0002 (1), male: 34.4 mm SL; Cameroon: Anga’a River, approximately 10 km from Yaoundé, 3 ° 52 'N 11 ° 31 'E. MRAC 95 030P 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 95 030P 14431448 (4), 17.4 –27.0 mm SL, Cameroon: Mvong River, tributary of Kong River, 2 ° 48 'N 11 ° 39 'E. MRAC 95 030P 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. 2View FIGURE 2) and short (vs. long) tubercles on the dorsal and lateral surfaces of the head ( Fig. 3View FIGURE 3), from M. laevigatus in having a serrated (vs. smooth) anterior edge of the pectoral spine ( Fig. 4View FIGURE 4), rounded (vs. truncate) caudal fin ( Fig. 9View FIGURE 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.
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 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. 4View FIGURE 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. 1View FIGURE 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. 1View FIGURE 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. 1View FIGURE 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. 5View FIGURE 5).
Remarks. Although M. batesii appears to have a much wider distribution compared to all other Microsynodontis from lower Guinea ( Figs. 5View FIGURE 5, 7View FIGURE 7 & 13View FIGURE 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.
|Outer mandibular barbel length|
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