Synodontis afrofischeri Hilgendorf, 1888

Englmaier, Gernot K., Blažek, Radim, Zimmermann, Holger, Bartáková, Veronika, Polačik, Matej, Žák, Jakub, Mulokozi, Deogratias P., Katongo, Cyprian, Büscher, Heinz H., Mabo, Lwabanya, Koblmüller, Stephan, Palandačić, Anja & Reichard, Martin, 2024, Revised taxonomy of Synodontis catfishes (Siluriformes: Mochokidae) from the Lake Tanganyika basin reveals lower species diversity than expected, Zoological Journal of the Linnean Society 202 (3) : -

Synodontis afrofischeri Hilgendorf, 1888

( Fig. 13; Supporting Information, Fig. S9)

Synodontis afrofischeri Hilgendorf, 1888: 77 [type locality: Southern shore of Lake Victoria (Victoria Nyanza), Mwanza district, Tanzania].

Material examined: Type material: ZMB 12745 , holotype, S. afrofischeri , 104.9 mm SL, southern shore of Lake Victoria (Victoria Nyanza)), Mwanza district, Tanzania, coll. Fischer.

Non-type material: BMNH 1971.6.22.111–113, three, 119.9– 127.7 mm SL, Kasanda Bay, Malagarasi River, Lake Tanganyika basin, Tanzania, coll. Greenwood , Lowe-McConnell, Lockley . BMNH 1971.6 .22.116, one, 145.0 mm SL, Katare, Lake Tanganyika basin, Tanzania, coll. Lockley , 1950. BMNH 1982.4.19.951–955, two, 108.4–151.6 mm SL, Lake Victoria near Rusinga Island , Kenya, don. Kisumu Laboratory . MRAC 2011.003 .P.1220–1233, nine, 57.1–114.7 mm SL, Riv. Malagarazi, au village des marais Ku Mutongotongo , séparation plantation cannes à sucre et rivière, Burundi, coll. Banyankimbona , 2010. MRAC 2011.003 .P.1234–1235, one, 98.7 mm SL, Riv. Malagarazi, colline Gatonga, au confluent avec Muyovozi , Burundi, coll. Banyankimbona , 2010.

Diagnosis: Synodontis afrofischeri is distinguished from congeners in the LT basin by a unique combination of characters: axillary pore absent; no granular papillae on head, body and fins; dorsal spine sparsely pigmented and light brown; anal fin with abundant brown spots; 42–64 (median 49) mandibular teeth, arranged in six symmetric rows of replacement teeth; 33–57 (median 43) primary premaxillary teeth; 1–8 (median 4) secondary branches on inner mandibular barbels; and 38–39 (median 38) total vertebrae, with 20–22 (mean 21) caudal vertebrae.

Description: The general appearance of S. afrofischeri is shown in Figure 13 and Supporting Information, Figure S9; axial skeletons in Supporting Information, Figure S8M, N; and relative measurements, meristic counts, and coded characters are given in Supporting Information, Table S12.

Longest examined specimen 151.6 mm SL (female, BMNH 1982.4.19.951–955). Body moderately compressed laterally. Dorsal head profile and predorsal back rising straight or slightly convex to dorsal-fin origin at an angle of 20°–23° (against midline of body). Postdorsal profile falling straight to adipose-fin origin and straight or convex to caudal-fin origin. Body depth at anal-fin insertion greater than half of body depth at dorsal-fin origin. Head dorsoventrally compressed; depth at posterior eye margin almost equal to maximal cranium width. Snout blunt and usually shorter than half of head length. Mouth subterminal, with abundant papillae on lips; width 67.3%–84.3% of snout length. Eye diameter usually slightly greater than half of snout length.

Head, body, and fins without papillae. Occipitonuchal shield and humeral process rugose. Humeral process broad–elongated; maximal depth 34.8%–50.5% (N = 6) of its length. Axillary pore absent.

Adipose fin well demarcated and short; basal length 20.8%– 28.0% SL, extending over 42.7%–56.7% of distance between dorsal-fin insertion and end of caudal peduncle. Adipose-fin insertion distant to end of caudal peduncle. Dorsal fin with two unbranched and seven branched rays; dorsal spine moderately serrated on lower anterior edge, few serrae on upper anterior edge, posterior edge with 11–18 serrae; length of dorsal spine, excluding upper flexible part, 71.1%–110.9% of head length. Anal fin with five unbranched rays and eight or nine branched rays; longest branched rays extending beyond level of posterior edge of adipose fin. Pelvic fin with a single unbranched ray and six branched rays. Pectoral fin with a single unbranched ray and seven or eight branched rays; pectoral spine strongly serrated on anterior (25–43 serrae) and posterior (10–21 serrae) edges. Pectoral fin usually slightly shorter than pectoral–pelvic distance, but in some specimens reaching above pelvic-fin origin in folded position. Caudal fin forked, with 2 + 15 principal rays, upper procurrent rays 12–13, lower procurrent rays 12–13.

Mandibular teeth 42–64 (median 49, N = 13) (holotype 49), unicuspid, arranged in six symmetric rows of replacement teeth. Primary premaxillary teeth 33–57 (median 43, N = 13) (holotype 43), arranged in two or three irregular rows.

Maxillary barbels long, reaching beyond pectoral-fin insertion. Outer mandibular barbels 57.2%–87.8% of head length, with 3–6 (median 3, N = 13) primary branches, secondary branches absent (present in only one specimen). Inner mandibular barbels with 7–11 (median 9, N = 13) primary branches and 1–8 (median 4, N = 13) secondary branches.

Total vertebrae 38–39 (median 38, N = 10) (holotype 38), abdominal vertebrae 16–18 (median 18), preanal caudal vertebrae 2–4 (median 3), and postanal caudal vertebrae 17–19 (median 18).

Coloration: In life (Supporting Information, Fig. S9), body coloration variable, light brown or cream in colour. Body with marbled pattern of irregularly shaped dark brown or black blotches. Belly cream coloured, sometimes yellowish. Fins light brown, with abundant spots. Maxillary and mandibular barbels brown, maxillary barbels usually darker.

In formalin (initial fixation) and later transferred to 75% ethanol ( Fig. 13), coloration similar to that in live specimens, usually darker, and brown or dark brown, with marbled coloration pattern.

After long-term preservation in 75% ethanol, historical specimens light brown or cream coloured. Marbled pattern of brown blotches faintly visible. Fins lighter than body coloration.

Distribution and habitat: Widely distributed in eastern central Africa, especially in the upper Nile drainage including lakes Victoria and Kyoga (Poll 1971, Seegers et al. 2003). Recorded over rocky habitats in the littoral and sublittoral regions. In the LT basin, S. afrofischeri is known only from the Malagarasi River drainage (Poll 1971, De Vos et al. 2001) ( Fig. 1).